Handbook

MIL-HDBK-20416 August196$?

I

I MILITARY STANDARDIZATIO N HANDBO OK●

I

INSPECTIO N EQUIPMENT

DESIG N

EiklI AGO I0,17A

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Downloaded from http://www.everyspec.com

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,..r” DEPARTMENT OF ‘bERNsE

., .,, . .WASHiNGTON, D.C.

MILHDBK-204Inspection Equipment Desigri

1. This standardization handbook was developed by the Department of Defense in accordance withestablished procedure.

2. This publication was approved Ori 16 August 1962 for printing and inclusion in the military statld-ardization handbook ai?ries.

3. This document provides infoi’mition and guidance to persunnel concerned with the design of inspectionequipment. Tbe handbook is riot intended to be referenced in purchase specifications except for informa-tional purposes, nor shall it supersede any specification requirements,

4. Every effort has been made to reflect the latest information on inspection equipment design It is theinteht to review this handbook periodically to insure its completeness and currency. Users of this documentare encouraged tu report any errors and any recommendations for changes or inclusions to Headquarters,DSA, Standardization Division, Washington 25, D.C.

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MIL-HDBK-204

FOREWORD

1. This handbook is intended as a wide in standardizing and systematizing the design of inspectionequipment used by or for the Department of Defen%.

2. The information contained in this handbook is a correlation of standard definitions, terminology,tables, illustrations, and design data necessary for the preparation of inspec~on equipment drawings andInspection Equipment Lkts.

3. The handbook is to be used by all who are engaged in the design of inspection equipment by or forthe Department of Defense.

AGOI0117A


CHAPTER1.Section

CHAPTER2.Section

CHAPTER3.Section

CFIAmER4.Section

CHAPTER5.Section

CHAPTER6.Section

ACO10I17A

MIL-HDBK-204

CONTENTSmm

GENERAL PRACTICES FOR INSPECTION EQUIPMENT DRAWINGS . . . . . . . . . I1.11.21.31.41.51.61.71.8

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Teminolo~ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Quality assurance provisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Inspection equipment lists . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Inspection quipment drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Engin~ring orders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Analysis ofinspection requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Selection OfinspectiOn equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

II

ELEMENTS OF Inspection EQUIPMENT DESIGN . . . . . . . . . . . . . . . . . . . . . . . . . . 222.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.2 'tolerances andallowances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.3 General constmction practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.4 Materials; selection, heat-treatment & application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342.5 Protection of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46THE DESIGN OF THE BASIC GAGES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493.1 IntrductiOn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 493.2 Plug gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 523.3 ~]nggages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .._ 523.4 Snap g*ges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 543.5 Template gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 553.6 Flu&pin g~= . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . 563.7 Spanner gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .._ 593.8 CaliWrgages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603.9 COmparatOr gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ml3.10 Receiver gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 603.11 F]xture gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 623.12 In&eating type gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63INTERRUPTED DIAMETEN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654.2 Unified and American National threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

4.3 Other thread fores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 694.4 Involute sphnesand serrations . . .._-. ..-. __ . . . ..-- . . ..-. .-.. .---. . . . . . . . . . . . . . 70OPTICS IN INSPECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 825,1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 825.2 Mirrors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 825.3 Thesimple m~nifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 825.4 The micromope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 865.5 Telewopes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 865.6 Collimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 895.7 Optical tOOfing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 945.8 Optical projection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1095.9 IntifierOmetw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115NON-DESTRUCTIVE T~TING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1186.16.26.36.46.56.6

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118Llquidpenetmnts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118Magnetic patiicle testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121Penetrating ra&atiOn &ts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122Ultrasonics . . . . . . . . . . . . . . . . . . ...l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 123Eddy currents . . . . . . . . . . . . . . . . ..X . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

,.. .‘ill


Figure 1.2.3.4,5.6.7,8.9.10.11.12.13.14.15.16.17.18.19.20.21.22,23.24.25.26.27,28.29.30.31.32.33.

34.35.36.37.38.39.40.41.42.43.44.45.

AGOIOI17A

FiGURES

The principal index of inspection equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4'Fheindex ofinspection equiprnel~t. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Thelist of inspection equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6The list of inspection equipment numbers (basic list) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8The cross reference list (special inspection equipment) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9The cross reference list (standard inspection equipment). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Specification cOntrOl drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Mono.detail drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Detailed assembly drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 14Detailed assembly drav.illg with break. outs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15A.l engineering order . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 19Surface finish symbol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Fabrication byscre!vs (general practices) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Locating bydowels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ’29Locating by keyway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30Locating by back.up method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31De~igll Precautions toaidheat-treating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Thete.n basic gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48Flushpin formula for drilled boles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58Multiple flush pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59Comparator gages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61Dial andcolumn type airpressure indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63Length ofligbt waves ininches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81Inspection mirrors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Bench magnifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82Simple magnifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83Thernicroscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 84Thetoolmaker's microscope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85Thetelescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 87ThecolfimatO.r . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88Theauto+oll]rnator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90Reticle showing adisplaced image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 00VariOus types OfautO-cOllirnatOrs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92a. Micrometer eyepiece typeb. Sli@g microscope typ?c. Off-axis pinhole or slit typed, F]xture typeAngle comparison for900 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . WDirect angle check for900 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93Indirect +pglecheck . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . WChec&pg with as~ne.bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94The optical lever . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94Straightn~ss or flatness test_ . .._ . . ------------------------------------------------- 95

Parallelism test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95Squareness test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95Inspection ofa909prism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96Alignment telescope witb micrometers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96Alignment telescope constmction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97Alignment collimator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

iv


F]gure 46.

47.

48.

49.

50.

51.

52.

53.

54.

55.

56.

57.

58.59.

60.

61.

62.

63.

64.

65.

66.

67.

68.

69.

.70,

71.

72.

73,

7475,

76

77

78

79

80

81

82

83

84

tilL-tibBK-264

%.COllimatOi cOnstructiOn. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99Measuring tilt anddisplacement with acollimator andtelescope. . . . . . . . . . . . . . . . . . . . . . . 100

Diagram ofcollimator andtelescope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..i . . . . . . . . . . . . . . . . 101

Jigtransits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102

Thetiltihg level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

Targets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

a. Aligrirneht targetb. Disphicement targetc. Auto-reelection target& Mirror targete. Double-line tai’get

Horizontal tooling bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Vefiical tOOlingbai . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

Instrirn&nt scand.: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Theoptical mic~ometer . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Principle of theoptical micrometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Auto.c61jimation unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

Auto.ieflection principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

Projwti6n eyepiwe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Coinciderice level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Stfiding lev~l . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108Theop$ical square . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..- 109

PrOjectOr. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

Measuririg projector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112GagihgprOjectOi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

Stagirig fixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

a. Compensating typeb. Permanent +ignecl typec. Positiun locklng type

Pmpetiies ofhgbt\vaves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Production of interference bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115

Detetiination of flatness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

Band spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

Llquidpenetrant fiaw detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

Magnetization \vith electric current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

Yoke magnetization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

Prndrnagnetization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

Mlmradiography-priricipleofopeiation..............-....-.-..-..............._.. 122

Strai@t beam seaichunit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Angle beam search ut)its. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

Surface wave search unit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

Contact pulse reflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125Immersion pulse reflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

Throu@transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

Resonance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127Magnetic lines of force armmdasound test piece . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

Depressed lines of force dueto aflaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127

AGo L0117A v


.-

MIL-HDBK-204

Table I.II.

111.Iv.v.

VI.VII,

VIII.IX.x.

XI.

XII.

TABLESPM.

Gage tolerances (general) .." . . . ---------------------------------------------------- 23Plug andring gage tolerances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Adjustable snap andlength gage tolerances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24Finishes forgaging surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Surface finish applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27Load.deflections forhefical springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35General propetiies ofgagesteels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43Recommended hardness values andsymbols for steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45Gage materials andapphcations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47Gage design values and acme threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71P]tch diameter compensation for adjusted lengths of go thread ring gages for centralizing

andgeneral purpose acme threads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72PltcIldiameter allo\vances onexternal acme tbreads, general purpowand centralizi]]g . . . . 73

AGO10117A vi


MiL-HcJBK-204

CHAPTER 1. GENERAL PRACTICES FOR INSPECTIONEQUIPMENT DRAWINGS

1.1 INTRODUCTION. This chapter establishesthe basic terminology pertinent to the intent of thishandbook and outlines all the general procedures

applicable to inspection equipment ivith the ex.ception of those involving actual design criteria.It preccnts the general approach to the InspectionEquipment Lists, the methods of preparing drawingsfor inspection equipment and the approach to theanalysis made prior to actual design.

1.2 TERMINOLOGY. Thcce DaI%i[aDhs en-deavor to provide a cofimon lan~ag~ f~t thosepersons engagedin the ddsign of acceptance inspec:ticm equipment. For convenience, the terminologyhas been grouped into three primary wctions:General Terminology, Dimensional Terminology aidGage Terminology. Terminology pkxmliar to screwthreads may ’be found in H28, Screw Thread Stan-dards, for Federal Services.

1.2.1 GENERAL TERMINOLOGY. Theccterms are those which apply to no special categorybut are in common usage in relation to inspectionequipment design.

1.2.1.1 Piece. Apiece isthatportion ofapartorassembly that is not capable of ftirther subdivisionfor manufacturing purposes.

1.2.1.2 Pd. A part is the finiched piece ofassembled piece which is assigned a numbei and isthe smallest replacement unit in the design of anend item (bracket, resistor, toggle switch).

1.2.1.3 CorriporwtiL A component is a groiip ofconnected assemblies and parts which is capable ofoperation independently but may be externallycontrolled or derive its power fmin another sourre.(computer, transmission, electrical generator).

1.2.1.4 End Iht. Acombination dfcoinponents,as.wmblies, and parts which is ready for its intendedu&e.

1.2.1.5 Product. Product isthe general term forthat which is manufactured or produced in anyfacbbn.

1.2,1.6 Inspection Eguiprncnt. Any equipment

~utilized for examination of a product in order todetermine itsconforrnance todrawings orspecific~tions.

1.2.1.5 Gage. The term “gage”, as uced in thishandbook, shall refer to those devices or inecbanismsdesigned specifically for the acceptance or rejection

of Parts and assemblies so far as dimensional features

TAGO10117A4ctabe 1

are concerned. The term “gage” is not intended tocover test equipment (see below) or measuringequipment.

1.2.1.6 Test Equipment. Anydevice, mechanism,or instrument designed or required specifically forthe purpose of appraisal or calibration of the func-tions, electrical aspects, or other phenomena ex.bibited by the parts or assemblies to be tested,

1.2.1.9 MedswirtgEouiprrtertt. Measuring equip-ment is defined asthocc rleviceswhlcb individually,collectively, or in corijuimtioh with related itemsprovide for a range of dimensional measurements,

i.2.i bIA{EN810NAL TERMiN0L0Gy. Theterms listed iir this section are those which are mostfrequently encountered in the process of dimension-

ing and tolerancing both products and acceptanceinspection equipment. The subject is further de-fined in Mil-Std-8, Di~ensioning and Tolerancing.

li2.2.l Standard Size. Standard size is one of ascriesof recognized or accepted sizes.

1.2.2.2 Nominal Size. The nominal size is thedesignation which is used for the purpose of generalclassification,

1.2.2.3 Control Size. A control size is one whichis established to assist in fabrication of the part andis not gaged in acceptance inspection.

1.2.2.4 Desigrt Si.re. The design size of adimen-sion is the size in relation to which the limits oftolerance for that dimension are assigned, (usuallybased on computations or empirical data).

1.2.2.5 BwicSize. The basic size of a dimensionis tbe theoretical size from which limits of size forthat d~mension are derived by the application of theallowance and tolerance.

1.2.2.6 AUovJmce. Anallowance isanintcntionaldifference in correlated dimensions or mating parts.It is minimum clearance (positive allowance) ormaximum interference (negative allowance) betweensuch parts.

1.2.2.7 Tolerance. Tbe tolerance ou a dimensionis the total permissible variation from that dimen-sion.

1.2.2.7.1 Unitaterd Tolerances, Unilateral toler-ances are those which are applied to the basic ordesign size in one direction only.

1.2.2 .7.2 Bilateral ToZcranccs. Bilateral tolerancesare those which are applied to the basic or designsize in botb directions.’ The basic or design size


MIL-HDBK-204

may or may not be the mean size since the plus andminus tolerances do not have to be equal.

1.2.2.7.3 Gage Tolerances. Gage tolerances are

applied to the gaging dimensions of gages in orderto limit variations in size during their manufacture.The direction of the gage tolerance shall always bewithin the product limits.

1.2.2.8 Clearance. A c~eiranw is the actualmeasured difference between mating parts.

1.2.2.9 Limits. L]mits are the maximum andminimum sizes permissible for a specific dimension.

1.2.2.10 Fit. The fit between two mating partsis the relationship existing between them with re-spect to the amount of clearance or interferencewhich is present when they are assembled.

1.2.3 GAGE TERMINOLOGY. Tbe followingterms are the most commonly encountered withreference to gages alone, Additional definitions

aPPeaf in Commercial Standard CS8, Gage Blanks.1,2.3.1 Gouernmenl Final Inspection Gages.

Government Final Inspection Gages are those usedby or for the Department of Defense in the accept-ance inspection of the finished product. These

gages must insure that the product has been manu-factured within the limits specified on its drawingor that the product is functionally acceptable.

1.2.3.2 Manufacturing Gages. Manufacturinggages are those used by the contractor in productionand are also known as process or work gages.

1.2.3.3 Gaging Aids. Gaging aids are designedfor itemswhich are not produced in large quantities.These aids arc used in conjunction with measuringequipment, i.e., surface plates, test indicators, pre-cision measuring blocks, and require a much higherdegree of skill in their use than gages,

1.2.3.4 Gage Base. A gage. base is that portionof the gage to which gaging members and mechan-isms are attached for complete assembly.

1.2.3.5 Gage Blank. A gage blank is the stand-ardizedform of tbe gage prior to heat treatment andfinishing. The term usually applies to the gageblanks shown in Commercial Standard CS8.

1.2.3.6 Gage Frame, A gage frame is the bodyportion of the gage (usually portable) as distinctfrom the gaging pim, gaging buttons, anvils andadjusting or locking mechanism.

1.2.3.7 Gage Handle. The gage handle is that

portion of a gage which is employed as supportingmeans for the gaging member or members.

1.2.3.8 Gage Member. The gaging “member isthat integral unit of a gage which is accurately

finished to size and is employed for size control ofthe work,

1.2.3.9 American Gage Design Standard (A GD),The caption American Gage Design Standard hasbeen adopted to designate gages made to the designspecifications promulgated by the American GageDesign ‘Committee, as contained in CommercialStandard CS8.

1.2.3.10 Adjustable Gage. An adjustable gage isone which can be adjusted to any limiting dimensionwithin a given size range and locked in position.

1.2.3.11 Fixed Gage. A fixed gage is one which isfinished to an exact size and cannot be adjusted inany manner. It may be single or multiple piececonstruction.

1.2.3.12 Limit Gages. L,mit gages represent thelimiting sizes within which the work will be accept-able.

1.2.3 .12.1 Go Gage. A Go gage represents maxi-mum material conditions of the mating parts. Gogages control minimum clearance between matingparts.

1.2.3 .12.2 Not Go Gage. A Not Go gage repre-sents minimum material conditions of the matingparts. Not Go gages control maximum clearancebetween mating parts.

1.2.3.12.3 Maximum Gage. A Max gage repre-sents a maximum component limit such as depth,length or diameter, etc.

1.2.3 .12.4 Minimum Gage, A Min gage repre-sents a minimum component limit such as depth,length or, diameter, etc.

1.2.3.13 Functional Gage. A functional gage isone which is designed to sizes implied by the func-tion of the mating parts rather than to the actualsizes specified on the mating part drawings.

1.2.3.14 Muster. A master is a device made to tbehighest degree of accuracy attainable and used maiu-Iy for reference or calibrating purposes.

1.2.3.14.1 Master Gage. A master gage is madeto one of the specified (max or rein) product limitswithin a high degree of accuracy as related to theproduct tolerance. A master gage is used as areferee gage to accept or reject products which havepreviously been gaged and found to be borderlinecases.

1.2.3.14.2 Mmler Check Gage. A master checkgage simulates the product dimensions that are to begaged. The check gage is made accurately to withi II

2 AGO1011?A


I

Wroximateh .5% of the part tolerance and usuallyis made to either the max or min conditions, Mastercheck gages are for setting, acceptance or surveil-lance. *

1.2.3.15 Wear Limit Gage. A gage for deter.mining when a limit gage or functional gage hasworn to the maximum size permitted.

1.3 QUALITY ASSURANCE PROVISIONS.Section 4 of the procurement document (FederalSpec., Military Spec,, or Purchase Description) foran item is entitled, (Quality Assurance Provisions”It contains complete and detailed information con-

cerning the inspection requirements, classification,frequency of sampling, examinations, and the recom-

mended method of inspection or applicable testmethod necessary to determine conformance of theitem to specified requirements for acceptability,In order to facilitate a complete inspection and tosupport the inspection requirements, a certainamount of inspection equipment is needed. Thkequipment may be:

(a) Astandard orcommercially available item,(b) Designed specifically for the characteristic

or feature to be inspected.(c) Selected from existing Government stocks.

Whatever the case, the equipment must be supportedby related documentation in order to achieve theproper coordination between the item specificationand the inspection gquipment. It is recognizedthat each activity, due to differences in their needsand methods of operation, may have different

approaches in effecting this coordination. Thefollowing section presents the general approach t.othis problem by one service and M such is presentedonly as an example. The practices for preparationof drawings as governed by MIL–D–70327, Draw-ings, Engineering and Associated Lists, are nowstandardized, thus Section 1,5, Inspection Equip-ment Drawings, is applicable to all services,

1.4 INSPECTION EQUIPMENT LISTS. Theinspection equipment lists represent a completeorganized record of all the prescribed inspectionequipment required to support the quality assuranceprovisions for a specific item including all major andminor subassemblies. The lists also provide theproper coordination between the item or part to beinspected, the inspection equipment and the itemspecification.

1.4.1 COMPOSITION OF THE LISTS. De-pending on the complexity of the end item, the

MIL-HDBK-204

structure of the lists could consist of the type offorms shown below:

(a) Principal Index of Inspection EquipmentLists

(b) Index of Inspection Equipment Lists.(c) List of Inspection Equipment(d) List of Inspection Equipment Nwnbcrs

1.4.2 PREPARATION OF THE LISTS. TheIEL forms illustrated are S% x 11 and are designedto be prepared on electric typewriters employing 10horizontal characters per inch and 6 vertical charac-

ters per inch. Examples of the various lists appearin figures 1 through 6. A general description of eachlist is provided below.

1.4.3 PRINCIPAL INDEX OF INSPECTIONEQUIPMENT LISTS, This list lists all majorassemblies, sub-assemblies, orinstallations which arerequired fora complete end item when this end itemis a combination of other end items, or is of a verycomplex nature with a large number of sub-assem-blies or installations, For each assembly, sub-assembly, or installation listed, the Index to Inspec-.tion Equipment Lists number is shown together withtheactivity responsible for that particular Index.

1.4.3.1 Responsibility. The principal index isprepared at the discretion of” the activity respon-sible for the complete end item.

1.4.3.2 Numbering. The principal index carriesthe same seven digit part number as the assemblydrawing of thecomplete end item, See figure 1,

1.4.4 INDEX TO INSPECTION EQUIP-MENTLIAS’TIS. Thislist isarecord ofall the sub-assemblies and individual parts of an average enditem or of an assembly, sub-assembly, or installationwhich is a part of an end item of such complexity thatit requires a principal index. This list indicates byinappropriate symbol in the column preceding eachpart number whether or not the part requires in-speition equipment. See figure2,

1.4.4.1 “L” Defined. When the Letter “L”

appears inthecolumn preceding the part number, itsignifies that there is a L]st of Inspection Equip.ment for that part or sub-assembly in the completeset of Lists and therefore inspection equipment isrequired for that part.

1.4.4.2 “NL]’ Defined. When the letters “XL”

appear in the cOlumn preceding the part number, itsignifies that no inspection equipment is required forthat part and consequently no List of InspectionEquipment for this part will appear in the completeset of Lists.

AGO,0,,7A 3


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AGO,0,,7A


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L w873227 STAND, P I NTLE

NL F9873228 TRACKASSY, R I GHT(5EE INDEX IEL9873228)

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AGO,0117A 5


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6 ACO,01,7A


MIL-HDBK-204

1.4.4.2.1 Ezce.rtiue “NL’”s. Whenever the pro-portion of “NL’”S to “L’”s on a particular listwould become excessive (over 507.) of the totalparts, the parts need not be listed. A qualifyingnote must be placed on the first sheet of the list asfollows: “PartsL]sted on XXXXXXX Which DoNot Appear On This List Do Not Require Inspec-tion Equipment”. The number of the productdrawing that lists the drawing numbers of all theparts of the end item may be used,

1.4.4.3 Numbering. The Index to InspectionEquipment Lists generally carries the part numberof the assembly, sub-assembly, or installation draw-ing for the item for which. it is being prepared. (Anumber from a special series for indexes within aparticular service may be used if it is desired).

1.4.4.4 Auxiliary Uses. An index may also beprepared to record spare parts, partc common, andparts peculiar from similar major items which them-selves are no longer on active status, but for whichthere are continuing spare part or replacement re-quirements. ~~

1.4.5 LIST OF 1NSPECTION EQUIPMENTThis list records all the inspection, equipment re-

quired to inspect an individual part. The character-istic to be inspected, the type of equipment for theinspection and its stock number, are the basic infor-mation furnished by this list. Additional informa-tion may be added in accordance with the needs ofthe individual ssrvice. See figure 3,

1.4.5.1 Numbering, Each sheet is numbered byinserting the number of the applicable part in thespace provided after the standard IEL notation.The letter size of the part drawing is placed in thesmall block between “IEL” and the part number.In those cases where a letter or letters are used inconjunction with numbers to identify a part, theletter(s) will become part of the IEL number (IELALX1532, IEL FC2395, IEL SKFSA2217).

1.4.5.2 Assembly and Sub-Assembly Lists. Allinspection equipment used in the acceptance of acompleted assembly or sub-assembly shall appearon the List of Inspection Equipment for that ac-sembly or subassembly whether the features in-spected appear on the assembly drawing or on itsdetail drawings. Notes cross-referencing the listfor the asccmbly drawing shall appear on the listsof the details in place of the features that are gagedat as&mbly, If thiire are no features inspected atthe detail stage, a dummy list carrying only the cross--reference to the assembly drawing lists shall be pre-

AGO10117A

pared. The revision area of this list should bemaintained current with the detail drawing in orderto direct attention to the location of inspection equip-ment that may require revision.

1.4.5.3 Multiple Application. When an IELpackage is to be prepared for an item which hascommon parts with existing items, it is probablethat a substantial portion of the Lkts of InspectionEquipment has already been prepared. Par~speculiar to new items will require their own newInspection Equipment Lists.

1.4.6 LIST OF INSPECTION EQUIPMENTNUMBERS. This form provides an alpha-numeri-cal listing of all the inspection equipment stocknumbers pertaining to each item for which an Indexto Inspection Equipment Lists was prepared. Twoseparate types of Lists of Inspection EquipmentNumbers are provided, a Basic List and a Cross-Reference Lkt.

1.4.6.1 The Basic List. The Baise List lists all thenumbers alpha-numerically, segregating the Mil–Std numbers from the drawing numbers. Thedrawing numbers are grouped under each drawing

size “A”. “B”, etc. The Basic Lkt is shown infigure 4,

1.4.6.2 The Cross-Referenrc List. For thocc appli-cations requiring additional information on the list,the Cross-Reference Lkt is provided. It still pro-vides for segregation of Standard and Special in-spection equipment but it also lists for each stocknumber the various Lkts of Inspection Equipmentupon which it appears. Further, a column is pro-vided for other desired uses such as intilcatingmethod of supply, availability or similar information.See figures 5 and 6.

1.4.7 REVISION OF INSPECTION EQUIP-MENT LISTS. All of tbe lists except the List ofInspection Equipment are revised generally in ac-cordance with standard drawing practices.

1.4.7.1 Reuision for Lists of Inspection Ewiw~l.The revisio,> system for Lists of Inspection Equip-ment is based on the following:

(a) Whenever the part drawing is reviseddimensionally regardless of whether theapplicable equipment is affected, thelatest part revision date shall be added tothe List of Inspection Equipment.

(b) Tbe addition of a part revision date prnumber indicates a revisiou to the List ofInspection Equipment and, accordingly,a revision date shall be entered,


MIL-HDBK-204

—

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,lE~ 9873217

~

730j62 I7307622 (2)8657375729~~2s

COMPLETE.SET.OFWA81110SSHALLINcLuOCALL DR4WINWL15TE0BmowPLUS A1S1OFIMSPECTWNEOUIPUCMT”FORMIX WM8ERLAWLED“L’”ONINOEX

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729758b

7959920j9j9922

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7298200 (3 jffi5~03j’297~30

7ti97b29729752ti

MI L-STD 114j220-75 I-4033MlL S10 Ill

j220-751 -k247

MI L-STO 116

j220-75 I -4840

j220-75 I -484 i

MIL STD ill

5220-47 I -5690

5220-75 I -569 I

MIL STD 118

5220-747-9390

5220-747-9466

MIL STO 110

5220-743-0210

INOEX TO LIST:IEL 9873217

m

,. ..” .“ ,. ..,. .,tv Rwf( =2” Rwlwy ●. . nEovw~EON,,. *- ,“ LIST OF INSPECTION EOU4PMENT MJM8ERS FOm:

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lEL 987w71THIS LIST CONCERNS ● SPECIAL INSPECTION EOUIPMENT 0 STANDARO INSPECTION EOUIPMENTA C0MpLE7E sEr OF onhwwas 5HALL VNCLUDEaLL DRAwINGS L097co EJELOWpLUS . ‘LIST OF IN5pEcT10MEOUtPUEII1- FOR EACH NUMBER LABELED “L,, 0!( INDEX ,EL

;: EOUIPMENT PARTS NO . EOUIPMENT PARTS:~ NO.L STOCK NO.., 4PPLICABLE REOO Y STOCK NO Applicable eEoo

A729~b:3 A 9873219 I

A756k2 I 5 0 9873223 I

A865737 I A ;:$g:~ I

07307651 A 9873227 I

07307622 A 9873226 I

07567375 A 9873229 I

C72915& D 9873226 1

C~959920 A$;%:; : g

C7959922 A 9873222 2

C7959925 C 9873222 1 g

C7959918 A 9873222 1

D72982: A 9873226 1 ‘INOEX To LIST: ~

O&5&03 B~

9873223 I

F865&O: B 9873222 I L I ST OF NUBEI sIEL 9873217

fl k/UEN CROERI SPECIFY I ,?E“t. *E,,$,~ *CV REVIS,ON-. RE:W~~SY. IJ.,E , ,“ ~,~~ ,,” LIST OF INSPECTIONEOUIPMENTNWCRS FOR:

ORIG I NSTALLAT 10N, SU$PENS 10N

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THIS LIST CONCERNS O SPECIAL INSPECTION EOUIPMENT ● 5TANDAR0 InSpeCtiOn EOUIPMEN7a COMPLETE sET OF ORAWINGS SHbLL dNCLUOEALL DRAWINCS L,STCD OELOWPLU5 h ,,L157 of IN5pEc710NE0UlP14EN1- FOR EACH NUUBER LA9ELE0 “L” ON INDEXIEL;: EOUIPMENT PARTS NO ;: EOUIPMENT PARTS NO.; STOCK NO. 4PPL,CABLE REOO .5 STOCK NO APPLICABLE REOD. .

MI L-STD 114

5220-751-4033 9873222

MI L-STD 115

~220-75 I -42ti7 9873222

MI L-STD 116

5220-75 I -4840 9873222

5220-751 -k& I 9873222

MI L-sTD 117

5220-75 I -5690 9873222

5220-75 I -569 I 9873222

MI L-STD 118

5220-747-9390 9873222

5220-747-9466 9873222

9873226 (2)

!Xktz!’

52 10-790-023b 9873226

9873229 (3)

“,. .~,,$,@, “,, Rc,,s,o. -, RWfI#S.” 0,, [ ,.” O.,E s,” LIST OF INSPECTION EOUIPMENT NUWERS FOR:

CR16I I/\7/58 I NSTALLAT 10N, SUSPENS 10N

>“,,. ”,, “,”,,.,0

SUB14111CD

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IELI:l:::’:

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10 ACOIOIITA


Thk system represents the minimum procedures formaintaining Lists of Inspection Equipment current.However, it is not intended to prohibit the respon-sible installation from revising the List of InspectionEquipment hr all part changes (material and otherspecification changes as well as dimensional revisions)if desired. It is mandatory, for successful operation,which once established, the system used must be

maintained consistent without change withh thegiven installation.

1.5 INSPECTION EQUIPMENT DRAWINGS.Inspection Equipment Drawings are prepared inaccordance with MIGD-70327 Engineering Draw-ings and Lists and its complement of the first 31Mil–Stds. This handbook restates the basic pro-cedures set forth in MIL-D-70327 with additionaldetail concerning their application,

1.5.1 TYPES OF INSPECTION EQUIPMENTDRA WINGS. Inspection equipment drawings maybe either of two general types, detailed drawings orspecification type drawings.

1.5.1.1 Detailed Drawings. Detailed drawingsare those drawings which completely depict all theinformation necessary in the fabrication of an itemof inspection equipment.

1.5.1.2 Specification type drawings. When it isdesired to procure a device purely on the merits ofits performance or upon the manufacturer’s specifi.cations, an envelope drawing is prepared. It depictsthe device in outline or pictorial form only andspecifies the required performance or characteristicCS.The manufacturer’s name or model number shall notbe used; only industry standardized model numbers.When it is necessary to specify the manufacturer’sname and model number, a qualifying note may be

app~ed Or a specification control drawing maY beused. (See M~l+3td-7 and figure 7.)

L5.2 PREPARATION OF INSPECTIONEQUZPMENT DRAWINGS. Inspection equip.ment drawings may be prepared as Mono-Detaildrawings, as Detail Assembly drawings or as acombination of the two.

1.5.2.1 Mono-Dekzil Draw”ngs. Mono-Detaildrawings are those drawings which depict only onedetail or part per drawing, See figure 8.

1.5.2.2 Detail -.’i88fmbly Drawings. Detail as-

sembly drawings are those assembly drawings whichhave some or all of the dimensions placed on theasccmbly views in order to eliminate or reduce thenumber of separate detail drawings as in F@mes 9and 10.

MIL-HDBK-204

1.5.2.3 Selection of Type of Drawing. The choiceof drawing type is determined by several factors,The number of interchangeable parts, the necessityfor field maintenance and repair, the quantity to beprocured, and the method of manufacture, all playa part in the decision as to whether mono-detail ordetail assembly drawings shall be uced.

1.5.2.3.1 If the equipment is complex and can bebroken down into a large number of individual parts,some of which are standardized or interchangeable,and if it is utilized in field service operations or is tobe procured in large quantities, the mono-detailsystem is preferred. Most test equipment and auto-matic gaging equipment falls in this category,

1.5.2.3.2 If the equipment is not overly complex,contains relatively few standard or interchangeableparts, is procured” in small quantities, and is stockedand issued as an entity, then the detail ascembly

apprOach Ora variant is preferable. Most gages fallin this category.

1.5.3 CLASSIFICA TJON OF DRA WINGS,For purposes of standardization, stock control andidentification, inspection equipment and inspectionequipment drawings are divided into two generalcategories, Standards and Specials,

1.5.3.1 Standards. Standard inspection equip-ment is equipment that has a univercal applicationfor a specific function and whose physical charac-teristics have been “standardized at the Department

of Defense level. Equipment standardized andutilized throughout the Department of Defence isreferred to as Military Standard equipment.

1.5.3.1.1 Catatogi~, Catalogs have been pre-pared for the various types of Military Standardgages. The gages are listed in order of ascendingsize and are numbered in sequence.

1.5.3.1.2 Stand4rd Drawings. Drawings are pre-pared by the individual services for prototypes ofMilitwy Standard equipment or equipment that issimilar in design to Military Standard equipment

but is not included in the dimensional scope of theMil-Std catalogs. This equipment is referred to forconvenience as Standard equipment. Drawings areprepared for this equipment with the aim of ultimateinclusion in the Mil&Std catalogs.

1.5.3.2 Speed drawiW8. Special inspectionequipment drawings are thoce which are primarily

@pplicable tO One particular type of part and aresubject to individual design peculiarities. This doesnot preclude the possibility of special equipmenthaving multiple application, because the identical

AGO10117A 11


.. . . ._ _ . . .. . . _. .

MIL-HDEK-204

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12 AGO IOI17A


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AGO 10117A 13


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.MiL-HDBK-204

AGO 10117A 15


MIL-HDBK-204

partfeatures may re-appear on several similar items;e.g., diameter bourrelet for 105m2n shells, multiplelead threads, diameter of retaining ring grooves,etc. Special drawings shall require referencing ofthe applicable parts.

1.5.4 INSPECTION EQUIPMENT DRAW-ING PRACTICES. The methods of presentation,terminology, dimensioning and tolerancing, shallbe in accordance with MILD-70327 EngineeringDrawings and Associated Lists, the latest applicableMilitary Standards numbered 1 through 31, and asprescribed in this handbook,

1.5.4.1 Clarity. An inspection equipment draw-ing is, in effect, a legal document. Therefore, tbebasic for rejections shall be so indicated on thedrawing as t.o fully protect the Government fromaccepting inferior workmanship, especially in tbeevent of controversies which could result from misinterpretation of “the drawing. Therefore, it is of

the utmost importance that all drawings be clear inevery respect and. free from ambiguity at any point,To assure that tbe designer’s intent is clearly des-cribed, the following should be noted.

1.5.4.1.1 Enlarged Sec~ions. An enlarged sectionof the equipment shall be shown where the com-plexity of the particular detail makes such enlarge-ment’ essential,

1.5.4.1.2 Minor Clearances. Both important andminor angles, radii and chamfers must be toleranceto prevent the manufacturer from taking excessivelatitude on these features, thm causing the quiP-ment to function improperly.

1.5.4.2 Dimensioning and Tolerancing. The di-mensioning and tolerancing of inspection equipmentdrawings shall conform .to the practices set forthin M.IIATD–8, Dimensioning and Tolerancing,

1.5.4.2.1 Gaging Dimensions. Gaging dimensionsare tbo~ which control the location and accuracy of

WecisiOn gaging surfaces and, therefore, are of tbeutmost importance. There fore,. it is imperativethat these dimensions be carefully applied andaccurately checked.

1.5.4.2.2 Detail Dimensions. The detailed partsor pieces of inspection equipment sba,ll be dimen-sioned in a manner which will insure correct assem-bly and economical manufacture, Accordingly, thefollowing precautions should be taken.

1.5.4 .2.2.1 Positional Tolerances, The allowableeccentricity, misalignment and similar features be-tween various pieces or parts of equiument shall he

specified, especially when the requirements are of ahigher degree of accuracy than that specified inMILG/10944. If a dimension which is vitally

concerned with tbe function of the equipment, iscovered within the limits of accuracy of MIL–G–10944, it is recommended that a symbol and cross--reference to a note referencing MIL-G/ 10944 be

applied.

1.5.4.2.2.2 Dimensioning System. It has been thepractice to specify in decimal form those dimensionswhich are critical to the proper functioning or opera-tion of the equipment or which must be rigidly

checked in tbe acceptance inspection of the equip-ment, while those dimensions which are non-critical are specified in fractional form. Althoughthis system may be continued for convenience, it isno longer mandatory and conversion to the completedecimal system of dimensioning is recommended.

1.5.4.2.2.3 Application of Dimensions and Toler-ances. Detail assembly dimensions should alwaysbe carefully cross-checked to eliminate any possibleconflict. The tolerances should be carefully appliedon piece or detailed dimm~ons to assure that a,,accumulation of them will not cause inter fere,lcewhen assembling the part with its mate or mates.Further, dimensions shall uever be duplicated onseparate views or enlarged sections. (If it is ab-solutely necessary to refer to a dimemion in two ormore places on a drawing or set of drawi,,gs, thatdimensiou shalt be identified b,v a symbol which shallbe used as a substitute for the actual dimellsim]s i])all places where it. must be repeated, )

1.5.4.2.3 Reference Dimensions. Reference cli-mensions are applied to drawings as an aid in manu-facture and ac,:eptance inspection, Reference di.mensions shall be computed with an accuracy whichis in keeping with the degree of accuracy requiredfor the final product. For rigidly controled parts,the rounding of numbers should not be accomplisheduntil the final result has been computed, Measure-ments over rolls and wires, for example, are some-times given as reference figmes. (h’f11,–STD/ 120outlines various means for precision measurementsover rolls or wires and gives related formulae forcalculations.) All reference dimensions arc based onmaximum material conditions unless otherwiselabeled; for instance, a dimension based W] meaumetal con{ltion should be labeled, “REF MEA\””.Reference dimensions also should be used on dettailedpieces to indicate critical requirements which mustbe controlled at assembly.

16 AGO ,01,7A


1.5.4.3 Delineation ofCommercial Items. Drawi-ngs for commercial gages, equipment and relateditems such as bases, frames, clamps, etc., need onlyshow the necessary object line at assembly. Dimen-sions are not required unless the cmmnerc;al gage oritem requires modification or the designer believessome difficulty may arise in procurement,

1.5.4.4 Scale. Designs should be drawn to full

size whenever practical. small type gages, forexample may be drawn several times size to achievethe necessary clarity. The scale to which themajority of views and sections are drawn shall beentered in the prepared space as provided on thedrawing format, in fractional form such as 1/1, 1/4,or 2/1. The scale of each view or section drawnto other than the predominating scale shall beentered directly below the view or section’ as“SCALE 2/1”, In the event that an item is drawnseveral times the size, an outline of the assembly,drawn to actual scale, should be provided somewherenear the oversize assembly.

1.5.4.5 Abbreviations, MIL-STD/12 should beused as a standard for all abbreviations. In general,drawing notes and specifications describing fits,alignment and assembly requirements should notinclude abbreviations unl~ss the meaning is un-

questionably clear. On the other hand, the identi-fication data shall contain the maximum number ofabbreviations that may be used without sacrificingclarity.

1.5.4.6 Identification Data, The identificationdata to be applied to the equipment shall be asconcise as possible and consistent with the properprocedures as applied to the various categories ofequipment. Abbreviations shall be used as notedabove, Identification data shall never be appliedon any precision surface.

1.5.4.7 Cross-Reference. All special inspectionequipment drawings shall carry cross-reference to the

applicable part drawing number in the Applicationcolumn. Any other part drawings required toestablish critical dimensions shall be listed asreference parts,

1.5.4.8 Drawing !Pitks. The title applied to thedr?wing of inspection equipment shall conform toany accepted nomenclature for that equipment andshall he phrased in the inverted form as outlined inMIL-STD-28. (See also paragraph 3,1.1).

1.5.4.9 Drawing Symbols. Drawing symbols area considerable aid in keeping general notes to amm]mum.

MIL-HDBK-204

1.5.4.9.1 Hardness Symbols. Apreferredaeriesofhardness symbols is recommended so that each

appearance of a particular symbol will com,istentlYindicate thesame hardness; e.g., an asterisk (*) willalways mean Rockwell Hardness CM to c66 orequivalent. Such a series is shown in Chapter2,

1.5.4.9.2 Surface Finish Symbols. MIL-STD-10, Surface Roughness, Waviness and Lay, serves asa basis for specifying the required surface finish.

1.5.4.9.3 !l’olerancing with Symbols, MII.-STD-8, Dimensioning and Tolerancing, shall be thestandard for expressing tolerance symbolically,

1.5.4.9.4 Welding Symbols. MIL%TD/19) Weld-ing Symbols shall be used on drawings to ind]cate the

apphcatlon of all weld]ng processes,

1.5.5 REFERENCING OF SPECIFICATIONSON DR.4.WINGS. Those specifications pertainingto inspection equipment that are necessary to insmyunacceptable piece of equipment shall be referencedon the drawing of said. equipment.

1.5.5.1 Gage Specifications. MIL-G/lo944,Gages, Dimensional Control, covers the minimumessential requirements for all types of dimensionalcontrol gages. It also references all specifications

applicable tO gages and gage drawings, except thetwo noted below, Therefore, only MIL-.G/lo944need be listed on the gage drawing unless extremeclarity is required. There are two other newspecifications;

(a) MIL-G45653, Gages, Cylindrical Plugand Ring, Plain

(b) MIL-G45654, Gages, Plug and Ring,Thread

which are used in place of MIL-G/ 10944 on thedrawings for those particular type of gages.

1.5.6 RELATED PUBLICATIONS. The list-ing below presents those publications and documentsof major interest to the design of inspection equip-ment. Itisessential thateach inspection equipmentdesign agency maintain these documents current tothe latest available revision.

1.5.6.1 Specijfcations,MIL-G-10944-Gages, Dimensional ControlMILI-18422—Dial IndicatorsMIL--I456O7-Inspection Equipment, Supply

and MaintenanceMILD45608—Design

spection EquipmentMILG45653—Gages,

Ring, Plain

and Drawings of In-

Cylindrical Plug and

AGO 10117.4 17


%. — ..

MIL-HDBK-2@l

MIL-G45654-Gages, Plug and Rhg, Thread

MIL-D-70327—Drawings, Engineering andAssociated Lists

1.5.6.2 Standards,MIIATD-1 General Drawing PracticesMIIATD/2 Drawing SizesMIIA$TD-7 Types and Definitions of

Engineering DrawingsMIfATD,–8 Dimensioning and TolerancingMIL-STD-9 Screw Thread Conventions and

Methods of SpecifyingMIL-STD-1O Surface Roughness, Waviness

& LayMIL–STD–12 Abbreviations for use on Draw-

ingsMIPSTD-19 Welding SymbolsMI~STD–24 Revision of DrawingsMIL-STD-28 Drawing Titles, Approved

Method for Assignment ofMIL–STD–29 Springs, Mechanical Drawing

Requirements forMIESTD–30 Associated Lists (Data List,

Index List and List of Ma-terial)

MIL–STD-110 Gages, Plug, Plain Cylindri-cal, Go

MIfrSTD-111 Gages, Plug, Plain Cylindri-Cal, Not Go

MIL-STD-112 Gages, Ring, Plain, GoMIL–STD-113 Gages, Ring, Plain, Not GoMIIATD-114 Gages, Phig, Thread GoMIL-STD–I 15 Gages, Plug, Thread, Not GoMIfATD–116 Gages, Ring Thread, GoMILSTD–117 Gages, Ring, Thread, Not GoMIL-STD-I 18 Gages, Snap, Plain AdjustableMIL-STD-120 Gage InspectionMIL-STD–133 Thread Minor Diameter Go

Plain PlugsMIL–STD-134 Thread Minor Diameter Not

Go Plain PlugsMIL–STD-273 Gages, Plug, Thread Setting,

Class W, for Go GagesMIIrSTD-274 Gages, Plug, Thread Setting,

Class W, for Not Go Gages

1.5.6.3 Other Publications.Commercial Standard CS8, Gage BlanksScrew Thread Standards for Federal Services,

H281.5.5 APPROVAL OF INSPECTION EQUIP.

ML’NT DRAWINGS, The approval of inspectionequipment drawings shall rest with the responsible

activity. The procedures for approval set forth byeach activity shall guarantee compliance with thishandbook and related service documents in allrespects. In cases where design is accomplished bycontract, an adequate design liaison and surveillanceprogram is essential to educate the commercialfacility as to correct procedures, design specifications,drafting practice, etc., in order to insure an accept-able product for the Government.

1.5.8 DISTRIBUTION OF INSPECTIONEQUIPMENT DRA WINGS. The distribution ofinspection equipment drawings shall he in accord-ance with the procedures established by each respon.sible activity,

1.5.9 REVISION OF INSPECTION EQUIP-MENT DRAWINGS, Revision of inspectionequipment drawings shall be accomplished in ac-cordance with MI L–STD–24, Revision of Engineer-ing Drawings.

1.5.10 SECURITY CLASSIFICATION. Nor.rnally, inspection equipment drawings will not carrya security classification. However, if an equipmentdrawing in any way reveals the nature of classifiedmateriel, the drawing shall have the same securityclassification as the item to which it pertains.

1.6 ENGINEERING ORDERS. In accomplish-ing the distribution or revision of inspection equip-ment drawings, a formal document must be pre-pared to direct the attention of the contractingofficer to the engime ring action being taken, Thisdocument is referred to by variom names but is mostgenerally known as an Engineering Order. It is thedocument which acts as a basic transmittal a“ci coversheet to identify and summarize an engineeringrelease or change action, The Engineering Orderdirects procurement zmd contracting actiom intocontracts for procurement and manufacture ofGovernment materiel which is committed to produc-tion or is in the process of such commitment,See figure 11,

1.7 ANALYSIS OF INSPECTION REQUIRE-MENTS.

1.7.1 OBJECT OF INSPECTION. The objectof inspection is to insure that the part being inspectedconforms with all requirements specified either bythe engineering drawing of the part or by relatedspecifications.

1.5.2 BASIC CA T.EGORIES OF INSPEC-TION, There are three general categories ofinspection requirements: dimensional, performance,and material.


,MIL-HDBK-204

O, D#anc# C01?8 Em ORDERNo.ENGINEERIll@ORDER

FuM65511)BREIWLATION PERTAIHIM70 lUE USEOFTHIS FORNSEEORDN-WINAIIUALWEI 3 MO; tiance Mvis ion, Army IIMpection of mtince OATE:

Ordnance Agencies Concerned 1-2740

FloM*m eermg Uivi sion, Sub-OffIce, OTAC CIMU:O SYMBOLFocal Machinery & Chemical Corp. ,1105 Coleman St., San Jcse

DUAREIIEREBYIIOTIFIEOOFTIIE FOLLOwlNGENQINEERINOACTION,TOBE ;PP~lEo TO PROCURWR PRODUCTION0NL%UNOEIIINSTRUCTIONSISSUEDBY THE CONTRACTII03AQECY

OE8CRIPTIVE DATAhTERIAL (ORO ITEM) AUTNORITY

Carrier, Personnel, Pull Wacked, Armored, K1l.3 ZCS FOM65x.1EASONFORENOINEERIMOACTION:To overcome an impracticable pro- AOS Identification

This E@neering Order is issued to revise Suspension Support Arm108’/5oo6and 10875007 by increasing the radius of fillets from 7/32 to 1/2 atintersection of Arm uitb Trunnion and Wheel Sub Sosses.

molwATloN10FR16RPwmllon nAllBLE oMmREmumEOmDlllEATIMnlwcllDlo/nl*lmo

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AGO 10117A 19

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MIL-HDBK-204

1.7.2.1 Dimensional inspection requirements re.late to conditions of size, form, position, or assembly.

1.7.2.2 Performance inspection requirements re-late to the functioning of the end item or any of itssub-assemblies.

1.7.2.3 Material inspection requirements relate tothephysical properties of the item such asiveight,hardness, strength, etc.

1.5.3 RESPONSIBILITIES O~INSPECTION,

EQUIPMENT ENGINEER, It is the responsi-’bility of the inspection equipment design engineer tothoroughly analyze all pertinent product require-ments, prescribe the equipment deemed necessary toeffect a creditable inspection and design ,the equip-ment as required.

1.7.3.1 The inspection equipment design engineershall prescribe the necessary inspect~on equipment toinspect all defects excepting purely observationaldefects, Defects requiring comparison standardssuch as surface finish blocks, scratch and dlgstandards, etc., are not to be regarded as observa-tional defects.

1.7.3.2 The equipment design engineer Shall con-duct a thorough analysis of all aspects of theinspection situation in order to provide the inspec-tion equipment most consistent with the overallrequirements, This analysis is dis,cmmd in thefollowing paragraphs.

1.7.4 ANALYSIS ‘OF PRODUCT DRAW-INGS. As a prelude to the preparation of theinspection equipment lists and drawings, the inspec-tion equipment design engineer shall conduct a,thorough analysis of each part and its position andfunction at assmebly to assure that:

(a) The available part print is to the latestrevision.

(b) The dimensions as applied will insure anacceptable product and necessary inter-clwngeabili ty, and are in accordancewith MIIATD–8.

(c)” The tolerances as applied are to the maxi-mum practical value which will notimpair the functioning of the product.

(d) The dimensions and tolerances as appliedwill not create interference at maximummaterial conditions (except where de-

,, sired), and are consistent with identicalfeatures’ cm similar items which havedifferent model numbers.

(e) The dimensions conform to recognizedstandard preferred sizes for threads,drilled holes, splines, ball bearing hous-ings, bushings, etc.

(f) New drawings are not identical to drawingsfor established spare parts or otherstandards.

1.7.4.1 Recommended changes based on thisanalysis should be submitted to the responsible,product design activity,

1.7.5 ANALYSIS OF QUALITY ASSLJR-ANCE PROVISIONS. When quality assuranceprovisions are included in the specifications for theitem, the inspection equipment design engineer shallcheck to insure that:

(a) The Inspection Requirements are con-sistent in all respects with those previ-ously issued for an identical or similaritem,

(b) Inspection equipment has not been spe.i-fied for dimensions on the part drawingswhich do not appear in the InspectionRequirements.

1.7.5.1 In the event that clarification or revisionof the applicable quality assurance provisions isbelieved essential, recommendations should be ~“b.mitted to the activity responsible for these specifi-cations,

1.7.6 DETERMINATION OF INSPECTIONEQi71PMENT REQUIREMENTS. In the prep-aration of the equipment lists, the analysis ofspecifications and product drawings is of considerablevalue since this analysis will convey to the inspectionequipment design engineer the critical nature ofcertain dimensions and functions which should beinspected to insure interchangeability and properfunctioning of the item. Since the great variety ofinspection situations makes it virtually impossible toestablish rigorous rules for governing these require-ments, paragraphs 1.7.6.1 and 1.7.6,2 are offered forgeneral guidance.

1.7.6.1 Inspection Equipment is Required:(a) When specified in the Inspection Require-

ments issued by a material branch of theparticular department,

(b) For parts and sub-assemblies which arcsupplied as spares and which must beinterchangeable,

(c) For parts and sub-assemblies which are notsupplied as spares but which mate withspares,

20 AGO I0,17A


I

(d) Where the dimension is critical with regardto the proper functioning of the item.

(e) For special requirements m specified in theoverall item specifications,

1.7.6.2 Inspection Equipment is Generally NotRequired:

(a) For non-critical sizes having large toler-

ances or which are manufactured bymethods which consistently reproducethe required size such as die-casting orstamping.

(b) For dimensions controlling the fit of onepiece with another which are perma-nently attached (as by staking, solderingor welding) prior to acceptance inspec-tion.

(c) For most ‘atmospheric fits” where varia-tion in size or contour will not causeinterference or disturb the functionalcharacteristics of the item.

(d) For dimensions not specifically defined ontbe part drawing. (Example: Hole ahownon a, centerline but having no d]mensionor toierance for its exact location mdwhere the location will affect neitherinterchangeability nor the functioning oftbe item.)

(e) For dimensions specified without toleranceor limits and possessing no functional

value. This includes “reference;’ “ad-visory, “ “construction, ” and “control”dimensions.

1.7.6.3 Justification of Eztent oj Inspection Equip-ment Design. In planning for the design of acomplete set of equipment, the total cost of designand supply must be considered relative to the overallcost of manufacture for the complete item ofmateriel. As a general rule, the cost should notexceed 5V0 to 8% of the total monetary allotment ofthe contract.

1.7.6.3.1 Desiqn oj Inspection Equipment jmEzperirncntal Itan.r. Undesigning for experimentalitems, improvised methods of inspection should beemployed wherever feasible. Existing stock gagesshould be salvaged wherever practical to achieveeconomical gaging and maximum coverage. Thiswill effect the greatest saving to the Government,since only a small percentage of experimental itemsare standardized for high production.

MIL-HDBK-204

1.7.6.3.2 Design oj Inspection Equipment jor

Standardized Items. When design is initiated forstandardized items which will be produced in largequantities, design units can effect the greatest savingby providing gages and equipment having automaticor manxal quick-operating features. The highinitial cost of the equipment will be amortized by thesubsequent saving in inspection time.

1.8 SELECTION OF INSPECTION EQUIP-MENT. Tbe type of inspection equipment to beemployed in the inspection of a specific feature is

established when the equipment list is initially pre-pared. However, in the actual design of the equip-

ment, it may differ from the one first planned. Inselecting the type of equipment, it is economicallyadvisable to employ standard equipment if possible,When this is not practical, the design of specialequipment is necessary. The design of expensivespecial equipment should be limited to standardizedmajor items where high rate of production willamortize the extra cost.

1.8.1 REQUIRED ATTRIBUTES OF IN-SPECTION EQUIPMENT. Inspection equipmentchould possess certain fundamental qualities, name-ly: accuracy, practicality, and economy.1.8.1.1 Arcuracy. The name, “Inspection Equip-

ment” applies to tools of specific types, but the namein itself does not necessarily imply a high degree ofaccuracy. The equipment should be designed to doits particular job, and the degree of accuracy should

be commensurate with the accuracy required by thecomponent.

1.8.1.2 Practicality. A design must be practicalfrom a standpoint of both operation and manufac-ture. A good design should provide ease of appli-cation with a minimum loss of time and motion tothe operator. Further, design considerations shouldminimize excessive or intricate machining andfabrication problems. Fhally, thought should begiven to the acceptance inspection of the equipmentand, accordingly, to fully protect the Government,the drawing and applicable specification shall providethe equipment acceptance inspec~iun facility withdefinite grounds for acceptance or rejection.

1.8.1.3 Economy. As a piece of inspection equip-ment is only one of the many tools required toproduce the complete item of materiel, care must betaken to insure that it is economically satisfactoryfrom an equipment manufacturing and componentinspection viewpoint. However, precisiou and dura-bility shall not be sacrificed to economy.

AGO 10117A 21


MIL-HDBK-2Q4

CHAPTER 2. ELEMENTS OF INSPECTION EQUIPMENT DESIGN2.1 INTRODUCTION. This section defines basic

inspection equipment design practices pertaining toconstruction and fabrication, tolerances, materialand general specifications,

2.2 TOLERANCES AND ALLOWANCES

2.2.1 GENERAL. It is not the purpose of thismanual to deal with all tolerances. Only generalconstruction tolerances and tolerances to be appliedto gaging dimensions will be discussed in detail.

2.2.2 TOLERANCES FOR GENERAL CON-STRUCTION DIMENSIONS, The determinationof a suitable tolerance is governed primarily by thefunctional requirement of tbe dimension andsecondarily by the economy of manufacture of thepart. Where standard fits are involved, such as withscrew threads and anti-friction bearing mountings,the tolerances have been standardized and referencetables are available, In other cases, the deter-mination of tolerances depends upon experience inthe type of manufacture involved,

2.2.3 GAGE TOLERANCING POLICY. Gage”tolerances and allowances shall always be applied

! within the product limits, i.e., the extreme limits of‘ the gage must in all cases fall within the acceptable

product limits. The unilateral system shall be ucedin applying tolerances to gaging dimensions which.control the extreme product limits, The bilateralsystem is preferred in applying tolerances to gagingdimensions which are based on mean or intermediateproduct dimensions, such ac for location of holes,

2.2.4 TOLERANCES FOR .GAGING DIMEN-SIONS. The tolerances applied to the functioningdimensions of gage designs shall be in accordancewith tables I, II, and III, unless the tolerance

specified imposes an impossible machining problem.In the cace of large or complex gaging dimensionswhere the tolerance specified i“ the tables or cmn-

puted on the basis of ten percent of the producttolerance results in impractical tolerances, theproduct designer may allow additional tolerance ora larger percentage of the product tolerance will haveto bs consumed. To bc practical, the gage toleranceshould not be less than fifteen millionths of an inchper inch. On extremely large gaging dimensions,this figure will accumdate rapidly and ~onsume tbegreater portion of the product tolerance. Care mustbe taken to avoid tolerances that cause confusionbetween the product and gage due to excessiveencroachment upon part tolerances.

2.2.4.1 Tolerance8 for Maximum or MinimumLimit ,Gages. Where product dimensions are pre-scribed as maximum or minimum values without agiven tolerance, the gage tolerance shall be based onan assumed product tolerance of .01 or the sum ofthe tolerances on the dimensions making up theoverall dimension to be gaged, whichever is theIesscr value.

2.2.4.2 Tolerances Applicable to “After Painting”Gages. For thocc specific gages used to measuremaximum dimensions after painting, apply a gagetolerance based on 10% of thickness of paint or thetolerance specified in the tables for a componenttolerance of ,002 whichever is the larger.

2.2.5 WEAR ALLOWANCE. Wear allowanceshall be applied on all fixed gage contact surfaces toprovide a smalI amount of extra metal whichlengthens the useful life of the gage. Excepted fromthis rule are all Not Go gages, adjustable snap orlength gages which may be recet, flush pin gages,height or depth gages on which wear occurs on bothsurfaces in the same direction, certain classes ofthread gages, taper gages with greater than 15”included angle, After Painting gages, and gagesdesigned to reduce gage encroachment “Pen producttolerance through the use of wear-resistant materialssuch ac tungsten carbide, etc.

2.2.6 SPECIFIC GEOMETRIC REQUIRE-MENTS, The tolerances directly specified on gagedrawings for requirements such as concentricity,parallelism, perpendicularity, centrality, flatness,etc. shall be to the maximwn that will ~till insure anaccurate gage, but in general shall not exceed 10%of the part tolerance on that requirement. Themethod of specifying tolerance shall be in accordancewith MIL-sTD-8,

2.2.7 IMPLIED GEOMETRIC REQUIRE-MENTS, The general nature of gages requires thatconcentricity, parallelism, perpendicularity, central.ity and flatness and other requirements be main-tained within general close limits, A sectioncovering this is included in MIPG–Iog44 for theexpress purpose of controlling implied geometricrequirements.

2.2.6 SURFACE FINISH. The graphic surfacefinish symbol as outlined in Figure 12, shall be usedto designate the quality of surface desired. For

application of this symbol see tables IV and V.2.3 GENERAL COnStrUCtiOn pRACTICES.

22 AGO 19,17A

.—. .


,MIL-HDBK-204

“HIS TABLE SHALL APPLY TO:1.TAPER PLUG ANO RING GAGES (INCLUDEO ANGLE UP TO ANO INCLUDING 1500’),FIXEO SNAP GAGES, FLAT PLUG GAGES (EXCLUOING FLAT CYLINDRICAL TYPE).WEAR ALLOWANCE REQUIRED. COLUMNS li2, ANO 3 ARE APPLICABLE.

2. TAPER PLUG AND RING GAGES (IN CLUOEO ANGLE GREATER THAN 1500’). WEARALLOWANGE NOT REOUIREO. COLUMNS t? ANO 3 ARE APPLICABLE.

3. MAX AND MIN GAGES, E. G., DEPTH, LENGTH, ANO FLUSH PIN TYPES. wEARALLOWANCE NOT REQUIRED. 00LUMN Z APPLICABLE FOR f.’)TH MAX ANDMIN TOLERANCES

AGO 1011TA

TABLEL G.getolerance. (g.ner.[).

23


MIL-HDBK-2CM

THIS TABLE SHALL BE USED FOR ALL THIS TABLE SHALL BE USED FOR ALLCYLINDRICAL PLUG AND RING GAGES ADJUSTABLE SNAP AND LENGTH GAGES

— QO 6AOES —1 1-(TOLiCOL I COL 2

LE~cE ALLw&RCE ToLERAffiE

.0s t ,825

.025 1.610.00002.00003

I.S1O l?.slo .00004%610 4.510 MASTER4.5 I o 6.510

.00006

.000066.510 9.0109,0 I o 12.010

,00008.00010

;:xlf5J .00004:::: $:3:1,610 2.510s .0003

2.510 12.010 uSE APPROVED COMLMEASURINQ DEVICE

2.6 I o 4.s I o* .000104.5 Io 12.010 ,001 ‘J2E AWROVEO GOML

MEASURIN9 DEvICE.0s I .025.825 1.s10

.00010 ,00007

.00010 .000091.610 2.s10 .00008 .000122.510 4.5 I o .002 .00006 .0001 s4.s10 6.510 .0000s .Ooot 96.610 12.010 USE APPROVEO COML

MEASURING 0EwC6.Oa 1 ails .00020 +m$ ::.82s I.slo Sxll::1.510 2.s t o .000162.s I o 4.s10 .004 .000204.s10 6.510

.00020,00020 .0002s

6.5 I o 9.0 I o ..000 to .000s20.0 I o 12.010 .000 I o .00040.125 t.slo .008 .00040 .00030I.slo 2.s10 .00040 ,000402.s I o 6.310 L?P .000306.S 10 12.010

>000s0,00020 .00060

— NOT 00 6AGES —

SIZE RANGE COMPONENT WEARCOL 3

A30vE TOR lNCL ToLERm= AL~AN= ‘oLEw=.03 I .62s .00004

-.625 2.510 .0005 SNUG FIT ON GO%5 I o 12.010 USE COML MCAS OEVICE.W?s 1,s101.610 2.510

.00006.001 .00006

2.5 I o 4.s 10 .000 I o4.s 10 12.o1o uSE COML UEAS DEVICE4.510 6.510 .002 I .000 I s6.310 12.010 USE COML MEAS 02VIC24.510 9.0 t o6.010 12.010 .004 .00016

.00020.12s,S25 l%

.00010

.000121.510 2.510 .006Z.5 I o 4.s I o

.00016

4.510 6,S 10 u!.00020JJ:lxl;:

6.S 10 9.0 I o6.010 12.010 .000404tUSE FOR ALL GAGE6 REOUIRING AIR GROOVES

LANCESARE IN TEN-THOUSANDTHS OF AN INCH)

SIZE RANGE

I+H-t-w

#i

.O1t 45666 6

.01045S66 6

,00934 s5s5

.006 3 45s5

.OOT 13141515151

W+#.Oo1111 I I I I

1 PDR COMPONENT ToLERANCE ANO/OR SIZE RANGE WOT SHOWN, USE NEXT SMALLER COMPONENT TOL

TABLE H. Plug and nng gage lolmmce.% TABLE 111. Adjualable snap and length gage tolemnces

24 AGO 10117A


T . . . . . .. . –.-

2.3.1 FABRICATION2.3.1.1 Fabrication b~ Screws, This is the most

common method of fabrication. The length ofengagement should range from 1 to 1~ times thediameter of the screw. Smaller gages such asbuilt-up snap types and precision locating elementsof fixture gages usually employ a fine pitch screwwhile a coarse pitch screw is considered adequate forsecuring large fixture gage elements where precisionlocation is not of vital importance. Unified screwthreads shall be specified, Where angularity, align-ment or other types of precision location must bemaintained within ,005 or less, precision dowel pinsor keyways should be used in conjunction with thescrews. For general practices, see figure 13.2.3.1.2 Fabrication by Welding. Welding is fre-

quently used in the fabrication of larger equipment.It is a rapid, permanent, and economical means offabricating, For method of specifying welding by

MIL-HDBK-204

tage with welded constructions is the possibility ofdimensional change due to the gradual release ofinternal stresses set up during the welding process.A stress relieving or artificial seasoning treatment ofthe welded assembly should always be specified tominimize this effect. Gaging dimensions of a high,accuracy should never depend on welded assemblies.

2.3.1.3 Fabrication by Brazing, Soldering, etc.Brazing and soldering are used mainly for applying

carbide inserts, balk, and other wear resistant a“viisor locating surfaces to the equipment..

2.3.1.4 Integral Part US,F’abricaled l’ype. Manu-facturing economy and ease of salvage are prime

considerations in determining whether a part shouldbe made in one piece m fabriacted from severalpieces. Parts should be fabricated, if complexmachining and grinding operations can be elimi-nated, even though several additional simple

symbols, see MIfATD–19. The main disadvan- operations are requi~ed,

RECOMMENDED MICRO-INCH VALUESACCORDING TO SIZE AND TOLERANCES

SIZE RANGEAPPLY ~ TO ALLGAGING TOLERANCESLYING BETWEEN

ABOVE TO 8 INCL THESE VALUES,029 ,825 ,00003 .00009.825 I .510 .00004 ,000111.510 2.510 .00006 .000142.510 4.510 .00007 .000174.510 6.510 .00009 .000226.510 9.010 .00012 .000289.010 12.010 .00015 .00035

d dAPPLY 2 TO GAGING APPLY6 TO GAGINGTOLERANCES BEL- TOLERANCES ABOVEOW THESE VALUES THESE VALUES

AGO 10117A

‘~ABLE IV. Surface jiniah app/ica1im18.

25

~._._...


ENLARGED DETAIL OFSURFACE FINISH SYMBOL

FIGURE 12. SwJace finish symbol

2.3.2 LOCATION

2.3.2.1 Locating by Dowels. See figure 14. Toprevent relative movement between precisely locatedparts, hardened and ground steel dowel pins are used.They are often referred to as precision dowel pins,

However, in using dowels, workmanship plays animportant part in the final accuracy since a good fitis imperative. It isadvisable to use a dowel pin of

%6 diameter or larger to insure the Iikelibood of aprecision fit unless space will not permit. Whereverpossible, the length of engagement in each pieceshould be 1~Z to 2 times the diameter of the dowel.Where repeated disassembly and assembly is re-quired, the backing up method is preferred overdowel pins,

2.3.2.2 Soft Plugs. Where two hardened piecesmust be located with respect to each other, or a pinmust be located through a soft piece into a hardpiece, soft steel plugs driven into the hardened piecesare recommended to facilitate machining at assembly

2.3.2.3 Locating by Taper Pins. Taper pins areused for the same general purpose as straight dowelpins. However, they are less susceptible to faultyworkmanship. Taper pins are preferred because of

their positive locational repeatability and theirrelative ease of removal.

2.3.2.4 Locating by Keywa~s. Locating by key-ways is a suitable method of maintaining locationalaccuracy in one direction. However, the maindisadvantage to this method as compared to dowelsor taper pins is the higher cost entailed in themachining process. This may be reduced on smallerpieces by using the entire cross-section as a key.

A keyway will prevent shift in only one directionand, therefore, dowels are usually employed toovercome shift in the other direction. Keyways areused where locational accuracy must be maintainedon several interchangeable elements which arecommon to one particular piece of equipment. Theuse of keyways is highly satisfactory where thefactor of strength must be considered in rnaintiaininglocational accuracy. See figure 15.

2.3.2.5 Locating by Backing Up Melhod. By usinga finished surface to back up a gaging element,locational accuracy can be maintained. Two ii-ished surfaces in planes 90” apart will providelocational stability in two directions. ‘rbis particu-lar method of locating provides for repeated dis-

26 AGO 10117A


GENERAL:L THENUMERICALVALUESSPECIFIEDIN THESE TABLES REPRESENTTHE MAXIMUMALLOWABLEROUGHNESSON THE OESIGNATEOSURFACE.

2. REQUIREMENTSFOR NATURALFINISHES (CASTINGS,FORGINGS,ETC) SHALL NOT BESPEGIFIEOON ORAWINGS,

IRECOMMENDED VALUES

TYPES OF FITSSURFACES, ETC.

MIcRO- INCHVALUES

‘~lv]vlylwl’’vpvEQUIVALENT FINISH DESIGNATIONZaQ g ~ $lfi =_

$?3

FEELER OR SIGHTING SURFACES

PRECISION LOCATEO SNUG. PUSH. DRIVE I I

1 (FLUSH PINS) +-1 I

.,OR PRESS FITS +REFERENCE SURFACES FOR MEASURINGPURPOSES

I

ORIVE OR PRESS FITS •x- “

BASES OR I

j: ~.& [9M 0s! f f Cf Cf:J K-1 ff

~ >a a~

COMPONENT CONTACTING SURFACESPRESENTING LINE OR POINT CONTACT

GRITICAL SLIOE a BEARING FITS

LESS CRITICAL SLIDE FITS

I FREE OR’RUNNING FITS 1111I NON PRECISION LOCATED SNUG. PUSH. I I T ““”l

OVERALL CLEANUP FINISHES(HANO GAGES) I

OVERALL CLEANUP FINISHES [ fOTHER UNIMPORTANT MACHINED SURFACES) I I I I

I I THE CLASS FIT SHALL BE CONSIDERED WHEN SPECIFYING THE REOUIREO FINISH.OBVIATIONS FROM THE RECOMMENDED VALUES ARE PERMITTEO IF JUSTIFIED.

TABLE V. Surface /inish rzpplic.tiom,

AGO I0117A 27


—.- ..-. ---- -.-v ..-.

SCREW HEMM MAY bRUTRUDE WHEN

METHOO OF DETAILING (EXAMPLE – SCREW”A” )

1. LOCATION DIMENSIONS FOR COUNTERSORE SHALL BE SNOWN ON OETAIL OF PART

oSCREW ENTERS FIRST OR I A NOTE SHALL BE SHOWN “ FOR + SCH SCR,

X HOLES ‘:

2. THE PART THAT IS TAPPEO TO RECEIVE TNE SCREW SHALL HAVE A NOTE

o

“ + -XxNF–XB,

X HOLES, LOCATE FROM I

3, ANY INTERMEDIATE PARTS SHALL HAVE ANOTE’’FOR’+ SCR, XHOLES, LOCATE FROM 0“[PART ENTEREO FIRST).

FIGIJEE 13. Fabrication buscrms (general practices).

28 AGO 10117A


r MAX DISTANCE BETWEEN DOWEL PINSEFFECTS GREATEST ACCURACY

7

PREcISIONPUSH FIT

DRIvE FIT

LLENGTH OF ENGAGEMENTI 1/2 TO 2 TIMES blAMETER

/

L TWO TYPES OF KNOCKCUTWHERE POSSIBLE MoLEs (LOWER pREFERAELE)z

PRECISION 00wEL PINS USEO INCONJUNCTION WITH SCREWS TOMAINTAIN ANGuLARITY, ALIGN-MENT, ANO DIMENSIONALACCURACY.

L LOCATE ONE PIN OFF CENTER IF THE ASSEMBLYMUST BE MAOE IN ONLY ‘ONE WAY.

II

FIoum 14. ,?mcatingbydowel.x

AGO 10117A 29


- .,

MIL-HDBK-204

30 AGO 101I7A

KEYWAY ‘MAINTAINS ALIGNMENT OF ROLLERS WHILE PINSMAINTAIN SPACING BETWEEN ROLLERS.

I - - 7 l-l

l-l~2 PREFERRED

IF CROSS-SECTION OF KEYEO PART IS SMALL, IT IS PREFERABLETO KEY THE ENTIRE CROSS-SECTION INTO BASE TO EASEMACHINING.

— .-- —.. _._— —


. _

MIL-HDBK-204

PREVIOUS METHOD(LOCATINGBYDOWELS) ‘

-

NOTE THAT ANY SHIFT IN TOP PLATEi CHANG+S ANGLk AND POSITION OF DATUM.,,

PREFERRED METHOD(LOCATINGBYBACK-UP)

,1

t THIS METHOD THE ANGLE IS GROUNDINTO FLANtiS OF BA5E PLATE. ANY SHIFT IN TOP PLATEIILL NOTAFFECTANGLEORFOSITION OF DATUM.THEREFORE, DOWELPINS CAN BE ELIMINATED.

FIGURE 16. Locating by back-up methcxl.

31AGO,0117A

I

I

1 .-.


MIL-HDBK-2Q4

asaembly and assembly without loss of dknensionalaccuracy, See figure 16.

2.3.3 ADJUSTING DEVICES2.3.3.1 Screws. The use of screws is a very

common method for providing adjustments. A finepitch screw together with a locking nut will usuallysuffice for most purposss. Various type specialscrews are also used for locating and anti-backlashdevices.

2.3.3.2 Locators and Special Mechanism. Where

speed is essential in operation, quick acting adjustingdevices shouId be designed using locating buttonsand spring loaded elements to reduce. unit inspectiontime.

2.3.4 INTERCHANGEABLE, AND REPLACE-ABLE ELEMENTS.

2.3.4.1 An interchangeable element is one of arelated series which makes a piece of equipment

$ppljcable to several related items,2.3.4.2 A replaceable element is one that is subject

to extreme wear or impact and may require frequentrenewal. These type elements should be designedon an interchangeable basis.

2.3.4.3 Both replaceable and interchangeableelements shall be prepared on asparate d~awings andassigned a stock number. On’equipment drawingsutilizing these replaceable or interchangeable ele-ments, they will be shownon the assembly view, begiven a part number and proper reference made inthe standard parts block to their assigned stocknumbers.

2.3.5 STANDARD PARTS OR MECHA-NISMS. Astandard partormechanism isonetbatinapplicable to several similar type pieces of aquip-ment; for example, the bearing supports for shellconcentricity gnges. The development, and appli-cation of standard parts isto,beencouriged.

2.3.5.1 When a part or mechaniam is designed. thatcan be widely adapted for use on other pieces ofequipment, a separate drawing should be prepared.The parts should be cataloged or indexed to providean easy reference for the designer. The use ofstandard parts will generally reduce costs anddelivery time.

2.3.6 COMMERCIAL PARTS. The uae of comm-ercial p~s is preferred wherever their applicationis practical. In general, ‘procurement time and costsare less as compared to specially designed parts.

2.3.7 UNIVERSAL TYPE EQUIPMENT. Uni-verwd type equipment is one which gages a particularfunction on various sizes of one typ+ of material.

The equipment in itcelf is designed on an adjustablebasis to include the necessary size range. However,care should be exercised to insure that the expenseentailed to include a wide size variation will beamortized in application, It is often better toprovide a ceries of two, three, or four universal types

to cover a certain size range than to design anextremely expensive and cumbersome unit to covertbe entire size range. The development of universaltype equipment is to be encouraged, particularlywhere it can be applied to a series of experimentalitems which do not warrant individual equipment.The designer should employ as many standard parts,interchangeable elements and commercial parts aspossible in designing this type equipment.

2.3.8 CASTING uS, MACHINED PARTS.Generally, it is advisable to cast most bases andframes for large pieces of equipment. Elementswhich are difficult to machine or fabricate should becast, It is usually a definite economic saving tosupplant complex inachhed parts and large cumber-came pieces with castings when designing standardparts or equipment for standardized items.

2.3.9 QUICK OPERATING DEVICES. Com-plicated fixture gages usually are slow in operationand, therefore, the use of various quick operatingdevices is recommended to reduce the productin.spection time.

2.3.iO HELICAL COMPRESSION .4ND EX-TENSION SPRINGS. In inspection equipment,helical springs are used extensively on fixture typegages. They perform many functions such as: (a)returning moving parts to their original position,

(b) in. conjunction with arms or pressure pads tohold a component in a predetermined position whilebeing gaged, (c) to retract gaging elements whilecomponent is being positioned, (d) to automatically*at multiple flush pin type elements where it isimpractical for operator to seat each elementindividually.

2.3.10.1 Such springs, while important to tbefunction of the gage, generally do not require a highorder of accuracy in design or manufacture and ithaa heen determined there is a need for a simplifiedmethod of calculation for springs of this mature.Such a method is presented here. For completespring design data, consult MilX%d–29, Springs,Mechanical Drawing Requirements For.

2.3.10.2 The data in this section, with its accom-panying loaddeflection tabies, is sufficient forgeneral design purposes and is not intended for use

32 AGO10117A

.—. . .. .


on unusual designs for highly accurate springs. Alltabular values are slide rule calculations and are, ingeneral, rounded off but are sufficiently accurate forcommon use.

2.3.10.3 Three (3) basic factd are generallyknown at the start of any spring design problem.They are Load, Deflection, and Space and are predetermined by the type of action and method of loadapplication. Thece basic factors are then used to

determine tbe cecondary, design factors: W]rediameter, Free length, Solid length, and Number ofactive coils. .. . . .

2.3.10.4 Load (P) is the force built up by com-pressing or extending the spring to counteract an

applied ‘load in a mechanism, a knOwtr factor ofweight in pounds. Loads thould. be specified atsome definite compressed or extended length, not atsome deflected distance from the free length, S&thefree length should be a reference dimension. Toler-ances should preferably be applied to the loads.

2.3.10.5 Deflection (F) is the movement of z springfrom its free or unloaded length tn a premxibedoperating position, which “is established by themechanism for which the spring has been designed.Deflection pcr coil is the “total deflection of a springunder a given load, divided by the number of activecoils,

2.3.10.6 Space is determined by the movement and

dimensions nf tbe associated parts, the spring beingdesigned to conform to space limitations.

2.3.10.7 The type of ends should be specified onthe drawing. When an extension spring is required,the ends shall be depicted and dimensioned.

2.3.10.8 Active coils (n) are thocc coils whichpermit deflection under applied loads. All coils areactive in extension springs.

2.3.10.9 Wire diameter (d) is dependent uponload, de~ection and workhrg space, and should bespecified in decimals to eliminate any confusionresuIting from the various wire gauge sizes.

2.3.10.10 Free length is the overali length of springin a free or unloaded position. For compressionsprings, assume a free length 1~ to 2 times theworking length. For unusual .worhg length tuspring diameter ratios, this figure may requireadjustment.

2.3.10.11 Spring index is the ratio of the meanspring diameter to the wire dkmetcr. Tbe bestproportioned springs, from the standpoint of manu-facture and design, hive a spring index of between

MIL-HDBK-204 ,.“~.}.

7 and 10, although indexes from 6 to 14are frequentlyused.

2.3.10.12 SoKd length is the length of a compres-sion spring when it has been fully compressed andthecoils aretouchirg. Itequals thedlameterofthewire times the total number of coile.

2.3.10.13 Pitch is the spacing or dimension betweentbe individual active coils of a spring.

2.3.10.14 Initial tension is the load in poundswhich opposes the opening nf the coils of an extensionspring by an external force. It is wound into thespring during the.coiling operation. The spring willhave a uniform rate after the applied Inad overcomesthe load due to initial tension.

Uwoflhe Lcu&DeJkctionTable.

The values in the Load-Deflection tables representthe deflection per coil (f) of a spring under a load (P).Thevalues may beincreased or decreasedin directproportion toanydesired change in load (P). SeeTable VI.

Example #1. Design a compression spring towork in a ~“ bore and exert a force of 6 Ibs. at aworking length of %“.

Known: O.D. of spring ~ (.359)Load (P) 6 Ibs.Working Length ~Free Length 1. (ussumed)

Required: W]re diameter (d)Solid len~hNumber of active coils

In the ?& O.D. row of the, Load-Deflection tables,the nearest figure for load (P) to the stipulated loadof 6 lbs. is found to be the ‘number 5.69 lbs. with acorresponding deflection”per coil (f) of .064. Directlyabove these fignres, at tbe top of the column, findthe wire diameter whtch is .038. To find thedeflection per coil (f,) for 6 Ibs., divide the value of(f), .064, by the value for (P), 5.69, and multiply bythe required load (P) of 6 lbs.

f,=~Xi =.0675

The number nf active coils (n) is determined bydividing the total deflection of the spring (1 –. %j

= %) by the new deflection per coil (f*),

.375— = 51A active coils,3675

Total number of coils equals 5)4 active coils plus 2coils for squaring ends or 7?4 coils. .

,., .AGO 10117A 33


. .

MIL-HDBK-204

The solid length equals the wire diameter (d)multiplied by the total numberof coils.

.038 x 7% = .285

F]nal design values—

Data—.O38 wire diameter?@&O.D.ofc oil ~~61b. + .61b load at~“ compressed length.285 solid lengtb (given888 max figure if spaceis limited)

Ends squared

Reference Data-1. Free length7% total coils,

5% active

Example #2, Design an extension spring X60ut-side dkmneter, full loop ends, in”line, to exert a forceof 8 Ibs. at a 2. extended length inside loops.

Known: 0. D.ofspring~6 (.437)Load (P)81bs.Working Length 2. inside loops

Required: Wire ,diametei (d)Free length, inside loopsNumber of coils

In tbe X6 row of the Load-Deflection tables, thenearest figure for load (P) to the stipulated load of8 lbs. is found to be the number 9.14 Ibs. with acorresponding deflection percoil(f)of .076. Directlyabove these figures, at tbe top of the column, findthe wire diameter, which is .047. To find thedeflection per coil (f,) for 8 lbs., divide the value of(f) .076, by the value for (P), 9.14, and multiply bythe required load (P) of 8 lbs.

f,=~ X8=.066

Pitch equals the deflection per coil (f,) plus the wirediameter.

P = ,066 + .,047 = ,li3

Length of loop = Inside diameter of coil (assumed)= .437 - (2 x .047) = .343,Length over extended coils = 2. – (2 X .343) =1.314

Number of coils equals the Iengtb over the extendedcoils divided by the pitch.

1.314— = il.6 coils.113

Free length = 11.6 X .047 = ..545Free length inside loops = .545 + (2 X .343) = 1.23

F]nal design values—Data—.O47 wire diameter

~~eO,D. of coil

8 lb + .8 lb load at 2. extendedlength, inside loopsl?ull loop ends, in line

Reference data—”1.23 Free length, inside loops11.6 Tntal coilsSpecify initial tension if required

2.4 MATERIALS : SELECTION, HEAT TREAT-MENT AND APPLICATION.

2.4.1 GENERAL. The selection of a proper steelin the construction of a gage is one of tbe mostcritical decisions a designer has to make. In aneffort to remove some of the mystery surroundingsteel selection, chemical analysis, tempering, etc., itis the aim of this section to give the designer a briefinsight into the causes and effects of heat treatmentof steel and the role it plays in the field of dimen-sional control. A gage drawing, however, accuratelydrawn and perfect in detail, remains inadequate solong as the physical materials from which it is to befabricated are not judiciously chosen with respect tothe tasks the gage must accomplish. A gagedesigner must further be guided in his selection ofmaterial by the degree of production expected, notonly of the part to be inspected, but also of the gage.In other words, a gage for a high production partmay dictate the uee of cemented carbide gagingsurfaces instead of tool steel and a particular gagethat is expected to he made in large numbers (orbecome a basic or standard gage) may necessitatethe usc of a casting for a large part of tbe gage ratherthan machining tbe various parts from steel, whichis costly and time-consuming. The designer mustalto take into consideration the shape or generalconfiguration of the part when cclecting steel. Partsof uniform or nearly uniform sectiou can stand amore severe heat treatment than parts that haveirregular form or haye”””narrow protrusions. Fromthe foregoing, which are just a few of the tbiugs adesigner must consider when celecting steels, it canbe seen that material selection is of the utmostimportance..to the designer.

2.4.l.l””Heat ‘f’reatment (defined). It is oftenerroneoudy assumed that heat treatment of steel

applies pnly to the hardening and tempering of steel.According to the definition accepted by the AmericanSociety of Metals and the Society of AutomotiveEngineers, heat treatment is “an operation or combi-

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IK-204

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nation of operations, involving the heating andcooling of a metal or alloy in the solid state for thepurpose of obtaining desirable conditions or prop-erties. ” Heat treatment therefore includes harden-ing, tempering, annealing, or any other processwhich employs the use of heat to impart specialproperties to a metal. Heating andcooling for thesole purpose of mechanical working is excluded fromthe meaning of this definition.

2.4.1.2 7’/wor~o~ Heat Treatment, Carbon istbech]efhardening element of steel, Inafully annealedsteel, carbon isin a certain form called pearlit.e andif the steel is heated uniformly above a certaintemperature (called the critical or upper transforma-tion point) a change in the stmcture occurs and thepearlitebecomes austenite. (Itisinteresting to notethat the steel becomes non-magnetic at this pointand is one way of determining the correct hardeningtemperature.) Ifthesteel isallowed to cool slowly,the austenite changes back into pearlite at the lowertransformation point which is anywhere from 85° to215°F. be16wthe upper transformsAionpoint. Thesecritical points have a direct relation to the hardeningof steel. Unless a temperature sufficient to reachtheupper trmmformationpointis obtained, so thatthe pearlite may be chsnged into austenite, nohardening action cam take place and unless the steelis””cooled suddenly before it reaches the lower trans-formation point, thus preventing the austenite fromchanging back into pearlite, no hardening can takeplace. Whensteel”is cooled suddenly fromtheuppertransformation point to above 400”F. or to roomtemperature the austenite is transformed into a hardneedle-like structure called martensite. It is tbi$structure (which takes theplace oftbepearlite) thatdetermines the hardness of a steel of stated carboncontent, Tbe lowest rate of cooling which resultsin the transformation of austenita into martensitewithout production of any pearlite is called thecritical cooling rate; it is Iargely dependent upon thecarbon content of the steel, being greater for low.carbon steels than for high-carbon steels.

2.4.l.3Harderzabiltty, Theinformation in 2.4.1.2is bated on the assumption that the piece of steelsubjected to treatment is of such small size that thechange of temperature throughout its mass occurs ata constant rate. In actual practice, however, in apiece of steel of practical size, the outside surfacecools more rapidly because it is in direct contactwith the quenching medium while the center COOISmore slowly, with corresponding differences in the

AGO 10117A 37

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formation of thevarious microstmctures. Howeverrapid the cooling, therefore, martensite is formedonly as an outside layer, while the structure of theinterior may grade to coarse pearlite at the center.

The depth of the case of martensite depends to aconsiderable extent upon the size of the austenitegrains at the start of cooling; tbe coarser the initialgrain structure, the deeper isthehardening for anystated rate of cooling. Constitution of the steel isthe other important factor in depth of hardening;the action of alloying metals bas the effect of permititing transformation of the austenite to martensite toa greater depth than is possible with plain carbon

steel. Althotlgh alloying metals have a notableeffect upon the hardenability of steel, they havelittle effect upon its maximum hardness, which forany stated heat treatment is determined chiefly bythe carbon content.

2.4.1.4Anneafing ati Stress Retieting. Annealingmay be performed by one of several methods,depending on the results desired. The purposes ofmmealingmaybe: (1) to soften steel for greater easein machining, (2) to relieve stresses and hardnessresulting from cold workhg, (3) to refine the grainand reduce brittleness.

(a) FuttannediW—The sWelisumally placedin tightly closed boxes, heated to a

‘temperature about 100”F. above thecritical range, and held at that tempera-

ture for a period of at least one hour foreach inch of maximum section. Afterthe heating period, the steel is ordinarilyWowed to cool very slowly in the furnace.Cooling may also be accomplished byplacing it in some insulating rnaterialtaprolong the time of cooling mcomparedto unrestricted cooling in air. Fullyannealed stscl is soft and ductile and freeof internal stress.

(b) Sub-critical annealing-If alargeamountofmetal is removed by machining, con-siderable internal stresses can be set upin the steel. These stremcs are likely tocause dktortion in hardening, eventhough oil-hardening, non-deforming toolsteel is used. It istberefore desirable toremove these stresses before the tool ishardened. Sub-critical annealing orstress relieving is accomplished by plac-ing the steel in containers packed withprotective material mid heating to just


—%—7—.-—.-—- — -- - —

MIL-HDBK-204

below the critical range (about I050”F.to 1200”F.). The rate of cooling de-pends on the carbon content, the ra~decreasing with increasing carbon. It issomewhat more rapid than the rate usedfor a full anneal. The resulting productis less soft than fully annealed steel, butis practical y free of stresses.

(c.) Normalizing—Normalizing is a special caseof annealing and is intended to put thesteel in a uniform, unstressed conditionof proper grain size and refinement sothat it will properly respond to furtherheat treatments. Normalizing may ormay not (depending on composition)leave steel in a sufficiently soft state formachining. The steel is heated to shout100° above the critical range and heldthere just long enough for completetransformation to austenite. It is thenremoved from heat and allowed to coolin’ still air at room temperature.

(d) Sphemidi%ing-To soften high carbon steel

sufficiently for machining, it is spheroid-ized. Steel is heated for extendedperiods just above the critical range, thenthe temperature is allowed to fall to justbelow. the critical range and maintainedfor an extended period. Slow cooling isthe final step,

2.4.1.5 Hardening and.Quenches. Steel is hardenedprimarily to incremw its wear resistance, This isaccomplished hy heating in a furnace to a predeter-mined temperature and quenching in the propermedinm. The purpose of qnenching steel is to fixin it some of the structural changes or modificationswhich have been caused by heating the steel abovethe critical range. The more rapidly the steel iscnnled from the hardening temperature, the more

changes will be retained in the steel and the harderit will be. In view of this, it might be assumed thatthe more rapid the quenching the better the results,Th,s, however, is not always tree, because too rapidquenching sometimes causes internal stresses whichmay be harmful. It is therefore advisable to use themildest quenching which will cool the steel withsufficient rapidity to develop the required hardnessand penetration. The rate of cooling, which deter-mines hardness for any stated ,composition of steel,is adjusted by choice of quenching method, Inorder to obtain the maximum hardness of any steel,

it must be cooled from the hardening temperature ata certain minimum cooling rate. This rate is calledthe critical cooling rate and will vary for differenttypes and analyses of “steel. In the case of straightcarbon steels, the rate is very Klgh and as a result,carbon steels are shallow hardening because tbe heatcannot be removed fast ennugh to secure hardnessexcept in an area relatively C1OSCto the surface. Theadd]tion of alloying elements to steel reduces thecritical cooling rate more or iess in pmportiou to theamount and Kind of elements used, Steels contain-ing a relatively large amount of alloying elementscan be hardened very deeply because they willharden even at a comparatively slow cooling rate.The most common quenches are water, brine, oil,and air.

(a) Water—Quenching in water at tempera-tures below 100”F. provides rapid conlingand is used frequently for carbon steelsof a wide range of carbnn cnntent and formedium carbon low-alloy steels. Forcarbon steels, only water quenching issufficiently rapid to give full hardness.For maximum effect the water may beagitated violently or applied as a spray.

(b) Brine-When a piece nf hot steel is plungedinto water, bubbles of steam form aroundit, momentarily insulating the hot steelfrom the action of the cooling water.This may result in soft spots on tbefinished article, Quenching in a brineconsisting of 10% rock salt dissolved inwater, prevents thk, action. The saltcrystals that crystallize near the surfaceof the steel, as water is vaporized, explodeas they come into contact with the hotsteel and agitate the solutinn sufficientlyto break down the bubbles of steam.

(c) Oil—Oil is a slower and much milderquench than water. Because cooling inoil is less rapid than in water, oil quench-ing produces less rapid change of volumeand consequently much less distortionthan does water quenching. The oil isgenerally a mineral oil of sufficiently lowviscosity to permit free circulationaround the piece being quenched. Thequenching property nf oil is increasedmaterially by vigorous agitation.

(d) Air—If the degree of hardening obtainableby quenching in air is adequate for the

38 AGO 10117A


,.. .-— ,- . . ,,-———<,—. ~, ,.,.—. .W. ,- ,--- -

purpose for which the steel is required,that procecs has the advantage of givinga product with the absolute minimum ofintend stress and distortion, becauee thetransformation takes plnce relativelyuniformly throughout the mats of steel.With some steels of high alloy content,the transformation process is so slow thatcooling in still air produces sufficienthardness to make the steel suitable evenfor cutting tools,

2.4.1.6 Cnse Hardening.’ In order to harden lowcarbon (. 10~o to .25% approx.) steel it is necessaryto increase the carbon content so that it may respondto proper heat treatment, This involves twooperations. The first is tbe carburizing ‘operationwhich consists of soaking the pieie in a carbon-richmedium for a specified length of time, depend]ng onthe extant of carburization desired. The carbon willthen be absorbed by any surface that is exposed tothk medium, producing a thin, bigh~arbon caseranging from .8% to 1.2% carbon. The secondoperation is that of heat treating the carburizedparts so w to obtain a jmrd outer case and at therame time give the low-carbon core the requiredphysical properties. Generally, the piece may beheated and quenched in much the came way as ahigh-carbon steel or it may be quenched directly fromthe carburizing temperature. The various methodsfor carburizing the low-carbon medium alloy steelsare outlined below:

(a) Pack Carburtiing-The articles to becarburized are cleaned and packedloosely in a metal box with carbonaceous

material or commercial carburizing com-pounds. Carbonaceous materials includecoal, charcoal, charred bones, bone meal,and hide scraps. Barium, ammoniumcompounds, soda ash, and various saltsact as energizers in hastening the reac-tion, The box is then sealed and placedin a carburizing oven at a temperature ofabout 1700”F. for the desired length oftime.,

(b) Gas Carbuting-A process in which thecarburizing is carried out in an atmos-phere of carburizing gases such as carbonmonoxide, or hydrocarbons such asbutane, ethane, methane, or propane.The prucecc is Rexible and more accurate-ly controllable than pack carburizing; it

MIL-IitiBK-204

can be used to produce almost anydesired hardness, depth, or carbon con-tent of the case. Poti]ons of the workwhich do not require hardening may beprotected by 8 layer of copper plating.

(c) Nittiding-Nitri&ng is a process by whichextremely high surface hardneac com-bined with exceptionaOy high wearresistance can be obtained on steel.Nitrided steel is resistant to corroeionand fatigue. Parts may be mach]nefinished before nitriding, because prac-tically no distortion occurs during theprocecs and no further heat treatment isrequired. Large sections of work can behardened successfully by nitriding, Theprocess consists of heating the steel in anatmosphere of nitrogen (ammonia gas)at a temperature of approximately 950”F.for tbe desired length of time, thencooling S1OW1Y,Carbon steel, whennitrided, ie too brittle; therefore, specialnitriding steels have been developed,The principal nitride forming-alloying

elements are A1uminum, Chromium, andMolybdenum.

(d) Cyaniding-Cyrmiding is, in effect, a com-bination of carburizing and nitriding. Inthk process a thhr case between ,001 and.015 inch in thicknecc ie produced byimmersing steel in a molten calt bathcontaining a cyanide, usually sodiumcyanide. This procecs is followed byquenching.

2.4.1.7 T@mpering. When a piece of steel has beenhardened fully, it is hard, brittle and internallystressed to such an extent that it may fail in service,It is necessary, therefore, to apply to a piece ofhardened steel some tort of after treatment to makeit less brittle (and therefore tougher) or to relieveinternal stresses. This is accomplished by reheatinga piece of hardened steel to a relatively low tempera-ture as compared to the hardening heat and leavingit soak for a specified time, then quench~ng in theproper medium. This process generally causes thepiece to Ioce some of its hardness. It is this finalhardness that is specified on the print. It will besufficient for this section to merely outline thedifferent methods of tempering.

(a) Colw Method-This method takes advan-tage of tbe fact that as the temperature

AGO 10117A 39


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MIL-HDBK-204

of steel increases, it goes through variouscolor stages varying from light straw(380”F. approx) through dark blue (560°

aPPr’OX). A trained obccrver can ~sti-mate the temperature of. a piece of steelin this way to withhr about 20” of its truetemperature before, quenching.

(b) .4usMnpeting-An interrupted quench pro-cecs which consists of quenching the steel

in a bath of molten salt at a temperaturebetween 450”F. and 900°F., dependingupon microstmcture desired, and main-taining that temperature until trans-formation of austenite into bainite (anintermediate structure between marten-site and pearlite) is complete. The re-sult is a steel of great toughness andductility.

(c) Martempering–An interrupted quenchwhich consists of quenching the steel ina bath of molten salt at a. temperaturejust above the martenaitic formationpoint and held there long enough fortemperature equalization throughout thework, then removed and cooled slowly inair. The result is a fully martensiticstructure which has Klgh hardness andlow distortion.

2.4.2 EFFECTS OF ALLOYING ELEMENTS.An alloy steel is one to which has been added one ormore elements in addition to the carbon and thecmall amounts of sulphur, phosphorous, silicon andmanganese that are preccnt in all plain carbon steels.The effect of these elements is ,to impart to steel

certain properties that plain carbon steels do notpossess such as: increased hardenability (carbonsteels harden through only in thin sections), lessdanger of cracks and distortion in quenching, greatertoughness and ductility, and increaced wear rcsist-

arrce,(a) Carbon (C)-Carbon increases the steel’s

capacity to harden till about .90%

carbOn is reached when the steel will be-come file hard upon quenching. Addingmore carbon than this does not increacethe measurable hardness, but it impartsgreater wear resistance, A good averagecarbon content ccems to be around 1,05$70

‘ This makes a very hard steel with highwear resistance, yet is not fussy or sensi-tive. to heat treatment.

(b) Manganese M(n) —Manganecc imparts acertain amount of strength, toughness,and elasticity, It is present in all steelsto about .20% and can be present toabout ,50To before being regarded as aspecial alloy addition. Adding moremanganese increases the hardness pene-tration. In fact, so powerful is its effectthat the addition of about 1.60% manga.nese to a .90% carbon steel would causea 2“ cube to harden clear through to thecenter, whereas without the extra man-ganese, the depth of hardness would onlybe about ~.. Furthermore, it causessteel to harden so rapidly and deeplythat it is no longer safe to quench inwater but must be quenched in oil; the

steel now betimes an oil-hardening, non-deforming tool steel. Manganese alsohas a favorable effect on stability.

(c) Silicon (Si)—Silicon, like manganese, ispresent in practically all tool steels inpercentages of .10% to ,30’3& .4s analloy, silicon is almost never used alone,or simply with carbon. It is generallyuced in conjunction with some deephardening element like manganese orchromium to impart strength and tough-ness and help to increase the hardnesspenetration. As an alloy it may befound in amounts of ,50% to 2.0!70.When silicon is present in considerableamounts,, it has a tendency to decar-burize the steel in hardening.

(d) Phosphorous (F’) and S?.dphur (S)–Gen-erally regarded as harmful impurities.Present in all steels, phosphorous isthought to have the good effect, bowever,in increasing the steel’s machkabilityand resistance to atmospheric corrosion.Sulphur also helps a steel’s machinability.Sulphur and Phosphorous are usuallykept below a maximum of .03%. Ingood quality tool steels, it is not uncom-mon to find them below .015%.

(e) Chromium (Cr)—The prime benefits ofchromium are to increase the hardnesspenetration and to impart great wearresisting qualities. The increased wearresistance is not necessarily accompaniedby greater hardness. In sufficient quan-

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I

(0

k)

(h)

(i)

,.

tities it confers oil hardening qualities tosteel, though not as effectively as man-ganese. The low and medhm chromiumsteels do not hold size as accurately asmanganese steels, those that are waterhardening changing size even more thanplain carbon steels. A steel containing5.0% chromium together with 1.070molybdenum is very deep hardening andsuitable for air quenching. Steels of1170 to 14% chromium and 1.5V0 to2.2~o carbon, commonly caOed “highcarbon, high-chromium steels” have rela-tively high wear resistance, and may beeither oil or air hardened, and their

stability or size holding property is high,

N~ckel (Ni)—The use of nickel in toolsteels adds toughness and greater tensilestrength but has little effect on hard-enability. Its primary effect is to imparttoughness and wear resistance when usedin conjunction with some hardening alloy

such as chromium, N’ickel tends tomake the steel oil-hardening rather thanwater-hardening,

Tung.sta. (lV)-In amounts up to 1.5%tungsten gives high carbon steel in-creased wear resistance. In greateramounts, together with high percentagesof carbon, the steel will acquire such wearresistance as to be di5cult to grind,

When united with carbon, tungstenforms tungsten-carbide. The carbide isbrittle and must be bonded together witha tough metal like cobalt, and sintered(powdered) to form an insert usuallybrazed to an alloy steel,

Vamzdirm (V) —Elasticity is the specialquaIity imparted by vanadium. Some-times added in small quantities (about.15%) to plain carbon steel, it does notaffect hardness or hardness penetration,but toughens it by keeping its grain sizesmall.

Molybdenum (Me)-Molybdenum is moreeffective tha”nany other common alloyingelement in imparting oil-hardening andair-hardening properties to stsel. It hasthe greatest hardening effect of any ele-ment except carbon, but at the same time

minimizes enlargement of the grain, withthe result that ‘toughness is retained.Like tungsten, it increases red-hardnessand wear resistance. Molybdenum, how-ever, encourages decarburization in beattreatment.

2.4.3 STABILIZATION AFTER HARDEN-ING. When a piece of steel is heated above thecritical point as in hardening, the carbou and anyalloying elements dissolve into a dense, tough stmc-.

ture called austenite. On quenching, austenitetransforms only partially into martensite, aliarder,stronger, and larger crystalline structure. Thiscbarige tomartensiteis characterized by an increaseinvolume of the steel, creating internal stresses, Torelieve these stresses and to transform more austeniteinto martensite, tempering is required. Temperinghas the effect of decomposing s,omeof the retainedaustenite. One hundred percent martensite is theideal aimed at in tempering but is rarely realized.The remai~ing .wsAenite {s one of the chief causesof dimensional instability since at normal tempera-tures the retained austerite decomposes into mar-tensite causing cmali but measurable dimensionalchanges in a plus dkection because its product islarger in structure. High precision gages need astabilization treatment if they are to maintain theiraccuracy over a period of time, otberwisetheexpan-sion due to decmoposition of retained austenite willeventually change dimensions outsideaf thepcrmis-sible tolerance. These dimensional changes are onthe average (depending on analysis and heat treat-ment of the steel) of about .0001 to .0002 inch psrinch or smaller. Insignificant or ordinary tooling,they are important on precision gages, The object

of the stabilization treatment is to transfrom theretained austenite so that none remains which couldtransform later on. Sub-zero or cold treatmentstransform the retained austcnite almost completelyand renders the gage dimensionally stable. Gagesalso derive other benefits from cold treatments,Rockwell “C” hardness is increased two or threepoints, wear life in increassd and the probability ofgrinding cracks is reduced. Generally the coldtreatment process consists of heating the steel totempering temperature rmd then cooling back toroom temperature. This is followed by sub-zerochilling to about – 120”f?. in a refrigerator or dryice for a similar amount of time and then allowingthe steel to return to mom temperature. 1t maybe necessaiy to repeat this process three or four

AGO 10I17A 41


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times to achieve the proper stability. The gage isthen finish ground’ and lapped to si’ze,

2.4A MACHINE STEEL. Machine steel is atrade name given to any of the hot or cold finished,low-carbon, fres-machining steels, It is a relativelyinexpensive, easily obtainable, versatile steel thatfinds many applications in the construction of in-spection equipment. It machines eaailyr can bewelded withont the use of fluxes, and can be bent orformed to many shapes, It is exceptionally amenable

tn carhurizing and attains a high degree of hardnesswhen case-hardened. For large gaging surfaces thatdo not receive intensive wear and the gaging d]men-tion is not of a high degree of accur?wy, case-hardened, hot-finished machhe steei is recom-mended. The hot finished type is the more stableof the two steels and should be ussd in preference tothe cold finished type whenever machine steels areemployed to make up nr have a direct relation withany gaging dimension, A drawback of hot-rolled

steel is that it has a heavy scale that must be re.moved by machining. Cold finished machine stceiis probably more widely used because it has a clean,s&de-free surface and is available in a multitude ofreasonably accurate sizes and shapes. In fact, alarge portion of the time, it may be used in the as-finished cnndition with a minimum of machiningbeing required, other than sizing to length andtapping for screws.. Both types of machine steelhave a scrioue distortion factor, when being heattreated, due to the severe quench required., Ther:-fore, caution should be exercised when d:signingcase-hardened, machine-steel parts. Rapid changesof section and thin protrusions should be avoided,Generous radii and fillets should be, provided toprevent cracking during the heat treat process,

The*” limitations, however, should not cause thedesigner to shy away from tbe use of ‘the machinesteel; rather it is the mark of a good designer tominimize these drawbacks by taking them intoaccount and designing around them. Case-hardenedsteels, in fact, do nnt enjoy the wide application theyare capable of. With a little thought, the designerwill find that tbe glass-hard fine fini~es and toughcore of case-hardened steels will supplant many of theexpensive tool steels that are specified indkcrimi-nately today, When a part ii to be case-hardened,carbon steel (carburizing grade) should be specifiedin order to be sure of getting a steel with the mostdesirable and predictable properties.

2.4.5 TOOL STEELS. “TooI Steel” is& blanket

term that is generally applied to medium or highcarbon steels of special quality prepared by theelectric furnance method, held to rigid physical andchemical standards, and prnceseed with extreme carefrom ingot to finished product, The result is a steelthat hardens more deeply, has more wear resistance,yet can be machined with relative ease, Practicallyall tonl steels are of such a composition that they arecapable of attaining a high degree of hardness whensubmitted to suitable heat treatment. Tool steelsmay he classified under two headings: Carbon toolsteel and Alloy tool steel.

a. Carbon Toot Sfeel may be had in either water-hardening or oil-hardening grades. The grade de-sired should be specified on the drawing, The water-hardening grade may be specified for a large portionof the precision parts of inspection equipment thatreteive average wear, are of fairly uniform sectionand the desired properties are such that case-hardened steel will not suffice. Again the drawbacksof water-hardening steels are comparatively highdisto~ion and danger of crack]ng during beat treat-ing. Three of tbe main reasons for specifying tbeoil-hardened rather than the water-hardening gradesare:

(1) to get more wear resistance(2) To get a tougher steel(3) To secure greater safety and hardening

accuracy in heat treating

Tool steel should be viswed with care when selectingsteel for large parts or parts that are to receive in-tensive wear. In the former case, carbon steel withthe critical areas case-hardened is recommendedwhile in the latter case, tungsten+mblde inserts orsimilar wear-resistant materials are preferred. Forparts under the size of a 3N cube or larger than 1“in cross section and also parts of any size possessingabrupt changes of section or irregnlar sections,carbon tool steel (oil ,bardening) should be specified.

b. AUoy TOOLSteel is a steel that has had variousalloying elements, such as chromium, vanadium,tungsten, etc., added dining the steel-making process,

They are steels that possess wear-resistance equal totwo or more times that of ordinary steel and are

applicable to inspection equipment in the oil a“d airhardening grades, Oil-hardening, non-deformingtool steel comes under the classification of an alloytool steel and should be specified for parts that areof such intricate form that a minimum of distortion,deep hardening and extra wear life is desirable.Graphitic tool steel has much, the snmc properties

42 AGO101,1A


tiik-HDBK-204

AGO 10117A 43


Mlk,HDBK72Q4 ,

but the .wear..resistance. is. extremely high. .Highspeed ‘steel is an air..hardenirig’steel and is generallyused for parts that ‘have carbide inskrts braze/1 inplace @t %lii ‘paits must retain its ha;dness. Thedecision to tit~li;~ 6ne of these steels should take into

consideration their lacti of free machining propertiesand higher first cost; with the exception ,of graphitictool st@ which machines almost as easily is castirmx .Wbenevex it is desired to U% one of thesesteels,, the app]icahle federal, specification ‘shall bereferenced in note form at ;the top of the drawing or

below the steel selected. ~~ .c. Dn”U Rod is a high carbon steel wh]ch is

obtainable in numerous fractional and decimal sizeswith the outside diameter grcmnd accurately to size.

Gagernakers frequently substitute drill rod for toolsteel when making cylindrical’ part:. Being finishedon diameter, it is a very convenient material forpins, piugs, handles, buttons, m@l anvils or abortflush pins. It is a little more difficult to machinethan most tool steels, hut it’harde,ns r+.sily. On thedrawing, tool steel should be specified to climate thepossibility of low carbon drill rod being used.

2.4.6’ CAST STEEL. A good grade of cast steelwith properties, similar to that of tool steel is some-times used o? complex parts to economize onmachining operations .where the parts must later be

hardened. Cad steel is stronger than cast iron andvery tiugh, and for this reason should be used

instead of cast: iron on t@ equipment and any otherequipment that may be subject to considerable

shock or impact z2.4.7 CAST IRON. Most large fixture equip-

ment bases are made from fine grain, gray cast ison.It is also ueed for odd shaped memberswhich can becast m6re conveniently than they can be machinedfrom standard size stock, fine grained gray cast ironis suitable for most baks ahd small parts.

2.4.8, SEMI-STEEL. The chief application of

semi-st4el is a substitute for cast iron where thecasting; is very cornpIex’ and adde~ strength isneeded.< Various types of semi-ite$ offer ,wearresistant propeti] es, resistance to gra]q growth andthus greater dimensional statilfity.. f+emi-stsd can

be welded and lends itself to heat treating. .2.4.9’ SIN~ERED, “CARBIDES. The use ‘of

tungsten, tantalum ~or heron carbide is preferred ongaging surfaces which .me subject to extreme wearand where hardened steel “parts would require fr~quent *placement: The life of carbide surfaces farexceeds the life of hardened tuul steel, so that wear

allowance in. meet cases in unnecessary. Carbide

blanks are a powdered metal product, and are pro-duced to the desired form by pre-forming, sinteringand shaving. Consequently, any further formingor resizing can only be aocomplisbed by grinding.

Therefore, the inserts used for gaging surfaces shouldconform to the general forms or shapes commerciallyproduced,’ Where inserts are subject to impact or

shock, the proper grade must be selected. Insertsshould be supported or ‘<backed-up” from as manydirections as possible.

2.4.10 SAPPHIRE. Synthetic sapphire is next

to boron carbide in hardness and wear resistance.Its use is usually limited to smal} rings and plugs.Its non-magnetic and non-sparking properties makeit excellent for use in equipment for componentscontaining explosives.

2.4.11 MAGNESIUM AND ALUMINUM.

Magnesium alloy contains 85% magnesium, theremainder being aluminum, manganese and zinc.This chemical composition produces an alloy rela-tively strong and tough and At the same time verylight in weight. These characteristics make magne-sium alloy especially adaptable for frames and

handles particularly on large pieces of equipmentwhich ,rnust be carried to the job by. the inspector.The same general characteristics contained inmagnesium alloy are present in aluminum except toa lesser degree. In addition, this material is readilyadapted to test equipment where resistance tocorrosion must be maintained in tanks and otherliquid reservoirs.

2.4.12 BRASS, BRONZE AND COPPER.These metals and their alloys are generally used only

for accessories. Copper is especially adaptable forelectrical contacts, etc., ,on electronic equipment.

Brass can be used for name plates. Phosphorbronze is an excellent material for special springs.Bronze is frequently employed for bearings. Brass,bronze, beryllium copper and other similar non-ferrorp metals are used exclusively for ammunitioninspection equipment when any amount of explosivepowder is exposed, because of their non-magnetic andnon-spark]ng properties. Beryllium copper bas arelatively Klgh strength and hardnem value for non-‘feirous material and therefore it is excellent for thebody eections of non-sparking equipment.

2.4.13, PLASTICS, In times of emergency when

materials such as steel, aluminum, brass, etc., arenot available, this material is uxful for handles,guides, name plates, and otbcx accessories.

44, AGo 1011’7A


Mli-HDBK-204’

4. A LIGHT SEGTIONSHALL NOTABRUPTLYJOIN A HEAVYSECTION

PROBABILITY OFCRAGKINQ DURING

‘“EN’H’N”YALE:’::;;U;

2. USE AUXILIARY HOLESTO GIVEUNIFORM COOLING

v F. 4UXILIARYHOLE PROVIDESuNIFoRM SECTION

3. f’ART5 SHALL BE OESIGNEOWITHOUTSHARPCORNERSOR UNDERCUTSADJOININGTHIN SECTIONS

mm

7-.ILP5 INTERSECTING HOLES CONCENTRATE

STRAIN AT THEIR JuNcTION

-E!!!fz3=’6. BLIND HOLE5 SHALL BE ELIMINATEDWHENEVER POSSIBLE

ORILL THRUTO PREvENT

.B-

CRACKINO THRU ~——-——THIN SECTION -

————

T.COMPARISONOFQUENCHINGMEOIAFOR STEEL RELATIVE TO CRACKING

1--MOST SEVERE 14ANDENING MEDIUM2.QN-LESS SEVERE3*-MILDEST

WHEN THIN SECTION OR ODO SHAPED 20W10URC2JINOT BE AVOIDEO, AN ADVISONYNOTE SNAUS1ADDEO TO THE ORAWIMQ SPEOWYlU60tLON AIRHARDENING TOOL STEEI. TO LESSEN THEPOSSIBILITY OF CRACIONQ.

1=.IDmFmuuF.17. De.stiprecatdiunatiaidh.%ltreniinu.

TYPE STEEL THICKNESS ROCKWELLHARONESS,PREFERREDSYMBOLSOR EQUIVALENT REMARKS

YOOL STEEL UP TO .06S5 C50 70 Css + THE NARDNESS SHALL BE

TOOL STEEL .062S T081NCL .125 C85 10 Gso

TOOL STEEL

oBASED ON T14E THINNEST

,125 TO NINCL .1675 C60T0 Css MSECTION OF TNE6AIX

TOOL STEEL ABOVE ,1S7S C63 TO C66

THOS8 SERRATEOGAGEs { TOOL S7L) ~~ ; c60 MIN : “

SPRIN6 STEEL,c45T0cs5 f K=% &?&Ys-

MACHINE sTEEL,:

ISN 90MIN CASE OR PACI( HAROEN .02 MIN-0- DEPTH AFTER~RjNo\N@

QRAPHITIc TOOL STEEL I — CSI TO C64 A


Ml~HDBK-~

M@hd OjSpmr~ingSld m Drm”np

skd(hd-~nbtijFor soft portiom of innpectiou equipment that have a directrelation with a gwjng dimension.

,Steel (mfd+.tdwd)For posts, indicator bracke@ eiq mft parta that bcve noconnection with a gaging surface.

Carbon steel (curburizinp Pm&)-e hardenLarge gaging curfacea that am not highly accurate,diding

memfxxn,pins, pm-tn thatdo not receiveintensivewear:

C@on tool steel (wler.fwd)-hardeaFor precision parta of inspection equipment that me of fairlyuniform cection, that receive average wear &nd numt behardened.

f!orton tool skzt (ti[-hard)-hardenSmall parts where there is a danger of cracking or dwtxxtionduring hardening. Parts of irregular cection that receiveaverage wear and nmct, he hmdened.

Tool skel (nondeform., oif-hard)-hardenPartsof complex design where a minimum of distortion duringhrmhming and where uniform properties rmd a little cxtmwear life in desired.

Graphic &d a!etd-hardenGen.ma]ly m larger pm of inspectionequipment.wherea

long wear life is desired. Also recommended for threadplug and ring gages

Highspud wce-lwrdenPrccisio” parb of imp+cticm equipment where high wearresistance in deairrxf or parta that mast retain hardnmaafter brazing ccrbide inserts.

2.6 PROTECTION OF MATERIALS.

2.5.1 CHROMIUM PLATING. This is a prc-cecs whereby a thin layer of chromium is depositedon gages or parts of gages for the purpoxc of in-creasing wcnr life or the salvage or modification ofgages. Tests reveal that chromium plated CUrfacesoutwear the finest tool steels by from 2 to 19 times.When specifying chromium plating, the hardness ofthe bate metal should be a minimum of Rockwell

C60 to prevent chipping of the plate. The basemetal may bc a plaincarbonsteelto keep the costlow. A xurface finish of 16 microinches or betterxhould be specified on tbe baxc metal since chromiumplate follows with Klgh fidelity any surface irregulari-ties produced by machining.

a. DimcneionaJ Chromium Plating-Chromiummay be deposited on a pr+sized gage to the thick-ne~ of the wear allowance, genernlly in amounts offrom .0fYW5 ta .0002. A copper sulphate eolution

applied to the. gage will indicate when the wearallowance has been expended. The remainingchromium can then be xtripped and the gage re-plated. Dimensional chrome plating is generallylimited to plain plug and ring gnges.

b. Wew Sw@cc Plutzig--This method ie ucuallyemployed on precision parte of inspection equipment.A minimum thickncm of chromium plate aftergrinding to ei8e, is specified, usually, ,0001 to .0005.

c. Salvage Pfati~Ih dvnge or nmcfificatifmwork, thicknesses up to .02 maybe used. Expensiveinspection equipment may be roved by grindingworn areas and building up the surface again withchromium, then regrinding to size.

2.5.2 PROTECTIVE FINISHES. Bases, frames,handles, and other non-functioning parts of equip-ment xhould be protected by an enamel, a paint, orother cimi}ar commercial finish. Mil-G- 10944 setsforth the minimum requirements for painting and

other protective finiches applicable to gages. Black-oxide finixh may be applied to all non-gaging sur-faces, It hns poor corrosion resistance alone;however, it will prnvent finger marking. Whengiven a light coat of oil, the corrosion resistance isgreatly increawd. It has the advantages of beinginexpensive and recults in a surface buildup on theorder of .000G25 inches. Black-oxide finish is asurface discoloration and shall be applied to alloptical staging fixtures to prevent glare.

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AGO 10117A 47


MiL-HDaK-2q4

48 AGO 10117A


MIL=HDBK-204

CHAPTER 3. THE DESIGN OF THE BASIC GAGES r3.1 INTRODUCTION. This chapter presents

the design information pertinent to the basic gageswith the exception of thread, spline, and serration

gages which are to be found in the next chapter.

3.1.1 GAGE NOMENCLATURE. Current gagenomenclature is a conglomeration of functions,

appearances, and trade names. In an effort tobring some standardization to this nomenclature,ten basic gage types have been selected. They arenamed accord]ng to their physical appearancerather than the feature inspected or possible tradename. It is realized that there are always excep-tions but with a little ju~cious use of the namesprovided it is felt that nearly all gages can be placedin one of the following groups:

1. Plug 6. Spanner2. Ring 7. Comparator3. snap .8. Caliper4, Template 9. Receiver5. Flush Pin 10. Fixture

Tbe definition of each type and some backgrounddiscussion is provided in the following paragraphs.

3.1.2 PLUG GAGE. A plug gage is defined asany gage which simulates a male part or has anoutside measuring surface that tests the size of ahole.

3.1.3 RING GA GA’. A ring gage is defined asany gage of circular cross-section that verifies thesize of a single cylindrical or tapered surface. Thisdefinition is somewhat restricted in comparison withthe one for plug gages. This is done to provide aclear distinction between Ring and Receiver Gages.

3.1.4 SNAP GAGE. A snap gage is defined asany gage whose gaging surfaces are flat, paralleland opposing, separated by a frame or a spacer.Strictly speaking, (dictionary-wise) that which theindustry refers to as a Snap gage is a Caliper gage.It was felt, however, that usage of tbe term Snap isso common that it was doubtful if Caliper could besuccessfully applied; so the term Snap was retainedfor rigid frame devices with fixed or adjustable jawswhile Caliper was assigned to those gages with oneor more movable arms that actuate an indicatingdevice (see 3,1,8),

3.1.5 ‘1’EMPLA TE GAGE. A template gage isdefined as any gage which is merely a guide to theform of the work being executed, having either aprofile, a sighting surface, a scribe line or similarcomparison feature. It is proposed in this category

to include all the former plate type, length, depth,width, and height gages that were made from a

piece of M or % steel and presented steps, scribelines or profde against which the part was compared.Plate-type shaps were relegated to the Gage, Snap,F]xed category.. ,.

3.1.6 FLUSH PIN GAGE. A flush pin gage isdefined as one which utilizes a pin of known Iqngtbmoving in relation to a reference surface to ind]cateacceptability or unacceptability.

3.1.7 SPA NNER GAGE. A gage consisting ofa holder and precisely located pins or bushingswhich verify the relative position of features such asplain or threaded holes, bosses or slots.

3.1.8 CALIPER GAGE. A caliper gage is anygage with movable arms (or a combination of fixedand movable arms) that transfer a part featureinserted between or placed over them to an indicat-ing mechanism.

3.1.9 COMPARATOR GAGE. Any gage whichutilizes an indicating device to directly contact thework and indicate its departure from a preset sizewith a minimum of auxiliary devices. Thk categoryis tbe weakest of the group but was intended pri-marily to include those commercial or homegrowndevices with an anvil, column, base and indicatingdevice, either air, electric or mechanical. It is notintended to include optical projectors as opticalcomparators.

3.1.10 RECEIVER GAGE. Receiver gages areprecisely what tbe name implies. They receive thepart and verify its dimensions. Tbe name shall be

applied only to gages which consist predominantlyof internal surfaces or portions of surfaces arrangedto verify part dimensions. Gages consisting solelyof external surfaces shall he classed as Gage, Plug,Multi-Element. See paragraph 3.2.6 for morediscussion of this type gage.

3.1.11 FIXTURE GA GES. Any gage consistingpredominantly of devices arranged to verify the fea-tures of a part shall be labeled a fixture gage. Thedistinction is rather clear, it is believed,-tixturegage consists predominantly of devices, a receivergage of surfaces.

3.1.12 A list of sample gage titles follows. Theunderlined portions are for use where space con-siderations, on an lEL, for example, preclude use oftbe full title. Inverted nomenclature should be

applied to both drawing and IEL equipment listings.AGO 10117A 49


MIL-HDBK-204

PluggngeaGage, plug,adji.table!——Gage,plug, air——Gage, p>g, fl@Gage, plug, flat cylindricalGage, Kg, m~lt~&nent cylindrical.— .Gage, plug,spline. —.Gage,plug,spline,taper txmth msstw——. ———Gage, plug, surveillance c&k—.Gage, plug, taper——Gage, plug, taper thread——— -Gage,plug, taper threa$=ttingGage, plug, threa~——Gage, plug, thread-setting——. —

l<ing gaceaCage, ring, air——Gage, r@, plain—V,agc, ring, splint———Gage, ring, taper——(“:agc,&g, taper thrmd—.-Gage, ~g, &eacJ

Snap gagesGage,snap,plain ndjuatabl~—-Gage,snap, plain ~ustablo (!eng~b)—-G8ge, snap, fixed (builkup)..-—Gage, =P, fixed (solid)—.. .—Gage, map, indicating (mecb)——Gage, 9P, indicating (e=Gage, map, i=icati”g (.Q——Gage, ~p, splineGage, map, s~i;e-mllGage, Xp, tTre-&———-(hge, WMp,tbmud-mll—--—

Tmphlle gage,

(kg., Template, (r)rofilc)

WLgc, ~lwtc (Icngtb)

Gage, =plate (~cpth)

Cage, ~latc, (height)—.Spfmner gages

Gage, ymy~

Gage, 8~mmr2r,multi-pin,--—Gag., mumyr, multi-hole—(:age, 8Pw”er, i.diwtir,g,— --—

Flush pin wges(hge, Rwahpin, extcrml—— .(kigc,,flushpin, intcrnd———Chg., Hush pin, multiple—. —

)(8..10.? gqeaGage, receiver---- .,,Gage, :e:eiver, profileGage, recei;e;, ~ro~ile imd dignmmt----- .—

,.Firiwe gagesGage, d@lle

Gage,&turc, “=.ry[;age, fif@urc,flushpin—.(&c, @urc, i@icating

3.2 PLUG GAGES. A plug gage has been de-fined as any gage which simulates a male part orhas an outside measuring surface that tests the Szeof a hole,

3.2.1 PLAIN CYLINDRICAL PLUG GAGES.The most common form of the plug gage is the plaincylindrical plug. It consists of a single cylindricaldiameter ona plug coupled with a suitable handle,the best examples of which are the standards setforth in Commercial Standard CS8, Gage Blanks.

3.2.1.1 MiMaru Standards for Plain CylindricalPlug Gages. There are four Mil+td catalogscontaining plain cylindrical plug gages, Mil–Stds 110and 111 which are a general listing of available Goand Not Go plug gages and Mil-Stds 133 and 134which area listing of the Go and Not Go plug gagesused in the acceptance of the minor &lameter ofinternal threads. These gages bear no limitingidentification data so may be used for any suitableplain plug application, Each catalog is dkcussedseparately below,

3.2.1.1.1 M&Sti-120. This catalog is the primesource of Mil–Std Go plug gages, It covers therange from 0.31 t.o 2.510 inches inclusive and is

arranged in increments of .001 inches and .03125inches.

3.2.1.1.2 Mit-Std-lff. This catalog is the primesource of Mil-std h’ot Go plug gages, It covers therrmgefrom .031 inches toandinchldin g2.510 inchesin increments of .001 inches, It also includes gagesin increments of .0005 inches fora part tolerance of

.0005 across the range of .031 inches to and including

.8255 inches.3.2.1.1.3 Mil–Std-19S and 13’4. These catalogs

area listing of allthe Go and Not Gopiain cylindri-cal plug gages applicable to the inspection of the

minor diameters of standard classes of internalthreads. The gages are not marked with theparticular thrud designation but merely with thegage part number, function and size, i.e., 5220-7512800, Go .0465 so they may be universally

~ppliedto their particular hole size and tolerancecombination. Many of the gages listed thereindo not appear in Mil-Stds 110 and 111; therefore,these catalogs can be considered as a source of plaincylindrical plug gages.

50 AGO 1LI117A


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MIL-HDBK-204

3.2.1.2 Special Cylindircal Plug Gages. Thesegages are designed using the basic design datapertaining to standard and Mil-Std plug gages;but possessing a unique design feature such as a stepor cutout. Special plug gages should be designedso that they maybe modified from American GageDesign Standard Blanks whenever possible. Tbetolerances and wear allowances on gaging dimensionsshall be in accordance with tbe applicable tablesfound in Chapter 2.

3.2.1.2.1 Pilot Plug Gages. This type of gage isused to gage holes where the combhwtion of sizeand part tolerance is such that a pilot is requiredtocenter and start the gage in the hole.

3.2.1.2.2 Cylindrical Step Plug Gages. A cylin-drical step plug gage is a plain plug which has asurface ground perpendicular to its axis for use ingaging a depth. Thespecifications fortbecylindri-cal gaging features shall be identical to that for astandard type gage. The following should be con-sidered when designing gages of this type:

(a) Theplug must have achamferto clear theallowable radius in the bottom of thehole.

(b) The step surface on the gage must beimmediately adjacent to the part surfaceand must be accessible for feel purposesor for use with a straight edge.

(c) Thepart tolerance ondepth should be.005or greater since the accuracy of inspec.tion dependson feel.

(d) Clearanc. cutsorslotsmust reincorporatedin tbe design to clear obstructions.

(e) When thepart tolerance exceeds +%tbeuse of scribe lines is acceptable in lieu ofri step. Seeparagraph 3.5,2.l.

A single step is employed for gaging only one criticallimit of adepth, either maximum or minimum. Asingle step may also be placedon not go gages usedfor hidden surfaces to indicate whether the gage hasentered to or beyond the permissible limit. Twosteps me employed when the gaging of both limitsof a depth is required. In certain cases where thetolerance on diameter and depth of thehole is verysmall and the mating part entering the hole is aclose fit, it becomes necessary to use both a step plugandatlush pin. Thesingle step ontheplugisuwdto insure that thehole istheproper diameter to itsminimum depth and will properly receive the matingpart, while the flush pin is used to check the depthIimitsof the hole. Thetolerance onthe single step

AGO I0117A 51

on the plug shall be reversed (minus) to preventconfl]ct with the flush pin inspection.

3.2.1.2.3 Recessed Type Plug Gages. Some di-mensional features necessitate the design of pluggages containing various types of slots, cutouts, audcounterbores whlcb will clear protrusions locatedwithin the hole being gaged. Thk type plug shallbe modified, where possible, from an AmericanGage Design Standard blank and may berlesignedto either clear orperform a functional check on thelocation of the protrusion within tbe hole.

3.2.1.2.4 Functional Plug Gages. Certain partspecifications require that a plug of specific diameterand Iengtb must pass through the part. Care

should be taken to insure that the plug design ismade as light as possible and that a convenientmethod of handling is provided.

3.2.2. FLAT CYLINDRICAL PLUG GAGES.This type of gage is ess~ntially tbe same is a cylin-drical plug gage insofar as its gaging application isconcerned. When used as a Eat Go gage, it pro-vides a more critical inspection due to the reducedarea of contact as compared to that of a full circum-ference. The following features should be cml-

sidered in design:(a) An entering chamfer sbordd be used where

the part specifications will permit.(b) Lightening holes should be used on large

plugs to reduce weight.(c) Precision centers should be left to facilitate

inspection and reconditioning.(d) Plugs over 8 inches in diameter may have a

strap handle insulated from the gage toease the inspector’s use of the gage.

3.2.2.1 Tbe chief application of flat cylindricalplugs is on large diamete- holes where a full cylindri-cal plug would be impractical due to its weight.Another primary application of the flat cylindricalplug is as a Not Oo gage on critical maximumdimensions of holes since it will jick up out-of-roundness beyond the maximum limit which wouldnot be observed using a full cylindrical plug.

3.2.2.2 Depth checking steps may be included intbe design of a flat cylindrical plug gage as outlinedin paragraph 3.2.1.2,2.

3.2.3 ADJUSTABLE PLUG GAGES. Arljust-able plug gages are usually applied to low productionitems when the internal diameter to be inspected islarge and the part tolerance is greater than .003.The gage consists of a frame, a set of gaging buttonsand adjusting device. Adjustable plugs are stau-


‘MIL:HDBK-204

dardized ii both single arid” double end types insize ranges from; 2X to 12% inches approximately.Full details of preferred construction may be foundin Commercial Standard CS8, Gage Blanks.

3.2.4 TAPER “PLUG’ GAGES. “Taper pluggages are used for checking the various dimensionalIimitsbf ”taperedholes’such asdiametei, depthaudangle or taper. When gaging tapered holes, thedesigner should be extremely cautious t? insure thatthe design’ will sufficiently control all the partdimensions. Insomeinstances, itmaybe net$ssarytout.e a taper ftushpin ificcmjunction wit,hap\aintaper plug,

3.2.4.1 The control of the diameter of a taperedhole is usually attained by grinding steps on oneend of the plug gage which indicates the limit of thedistance itmayenterthehole. When itisneces.mryto measure the max and min limits of the taper orthe angle, two plugs are employed, one plug beingmade to the maxiruwn angle, and the other to the

minimum angle. When gaging the part, the maxi-mum tapered plug must wedge at the top portionof. the taper, while the minimum plug should clearat the top portion and wedge at tbe bottom, Thedesigner should provide for the removal of a qwwtersection of each plug to aid the inspection in checkingwhether those conditions prevail.

3.2.4.2 Preference should be given to.the datumdiameter system of dimensioning in conjunctionwith the use of a basic taper if the length of the taperis such that the taper is sufficiently controlled by thetolerance zone created. When tbelengthof taper isshort, a tolerance on the taper or angle is generallyrequired.

3.2.4.3 Dimensions over rolls may be given inaddition to the actual mandatory size controldimensions, but swh dimensions should be labeled“Reference’’o nt redrawing, Wear allowance shallnot be applied on taper plug gages for tapers over15” included angle since there is no problem ofsliding contact whkhwould cause rapid wear. Also,it is not necessary to chamfer the front end of theplug since there. is no problem entering the gageinto the part.

3.2.5 FLAT PLUG GAGES. Thistypeofgageisusually utilized in the inspection of the width of aslot or groove. In some instances, the Go membermay incorporate the maximum and minimum depthof a slot along with its basic function. Flat plugsare also employed in many fixture type designs.

3.2.5.1 A Go and two Not Go flat plug gagesmust be employed for a satisfactory dimensionalchick of a rectangular hole.

3.2.5.2 Flat plug gages should have enteringchamfers except where the shallow depth of a partwill not permit.

3.2.6 MULTI-ELEMENT PLUG GA GA’S. Thisgage classification includes all male gages composedof two or more gaging elements on a common axis.If the gage consists of only cylindrical or taper

elements, it shall be labeled as such, i.e., Multi-element cylindrical plug gage or Multi-clement t:aperplug gage. If is consists of combhations of these orother types of elements, it shall be referred to assimply a Multi-element plug gage.

3.2.6.1 Applications. This type of gage is usedprimarily to inspect the relationship of two or moreinternal surfaces. It maybe designed on the basis ofdependent requirements specifieci on the drawing orindependent requirements on a drawing which maynot be gaged ecomically separately.

3.2.6.2 Design Considerations. Each surface ofthe gage is deeigned to the minimum size of itscorresponding female surface less the allowablemisalignment per individual surface. In two ele-ment gages, tbe permissible misalignment may behalved and each half subtracted from the minimumpart size ij the surjaces are adjacent and OJthe samelength, If the surfaces are not adjacent or not thesame length one diameter must be held to theminimum female size and all the misalignmentsubtracted from the other diameter to avoid anyerrors induced by the angular displacement betweenthe two diameters. In gages with more than twoelements, it is preferable to reduce each &lameterby its individual misalignment. Individual limitgages shall be specified to control the sizes of thevarious elements of the component.

3.2.6.2.1 On the smaller gages, American GageDesign Standard plug gage blanks and handlesshould be employed, if possible. The drawing,in any case, should specify that the precisiotl centerson which the gage was manufactured should he leftto facilitate wxeptance inspection and surveillance.

3.3 RING GAGES. Any fixed gage of circularcross-section that verifies the size of a single maleplain cylindrical or tapered surface shall be classedas a ring gage.

3.3.1 PLAIN RING GA GA’S’. A plaiu ringgage is defined as one which verifies the size of asingle male plaitl cylindrical surface. There arc

52 AGO 101I7A


several basic design criteria that apply to ail plainring gages.

(8) Ring gages should seldom be “Wd a.s NotGo gages unless deformation of tbe partis a factor.

(b) Since large ring gages are awkward andexpensive, the use of an adjustable snapgage ie preferred for gaging large diam-

eters where the tolerance is not criticalor deformation is not a problem,

(c) When the part tolerance is .001 or less, it isadvisable to “use indicating type gagesfor all sizes.

(d) R]ng gages that are under ,075 in diameterrequire an acceptance check to facilitatechecking.

(e) When the part tolerance is .004 or less, orthe gage is used for 100% inspectionon high production items, or the partmaterial is different (brass, copper,aluminum, etc.) from the gage metal, asurveillance or wear limit check is re-quired which is a standard plain cylin.drical plug gage made to the mastertolerance in table II. In this case, itmay be desirable to fabricate the ringfrom a wear resistant material such aschrome plakd tool steel, high speedsteel, carbide, etc.

3.3.1.1 Military Standard Plain Ring (j’ages.There are two Mil–Std catalogs containing plainring gages. Mil-Std–l 12 contains Go rings andMil-Std-l 13 .Not Go rings,

3.3.1.1.1 Mi~-Std-l 12. This catalog contaim allthe Military Standard Go rings, It covers the rangefrom .059 to 2,510 inches inclusive, in increments of

.X31 and .03125 inches.

3.3.1.1.2 Mil-Std-2f3. This catalog contains allthe military Standard Not Go ring gages. Itcovers the range from .059 to 2,510 inches inclusivein increments of .001 of an inch and includes ringsin increments of .0005 for a part tolerance of .0005covwing the range from .059 to .825 of an inch.

3.3.1.2 Special Ring Gagw This category in-cludes all plain ring gages which are designed usingthe general design information pertaining to Mii-Stdring gages, but which possess a unique design featuresuch as a step or cutout. In designing special ringgages of any type, consideration should be givento the following:

MIL-HL?BK-204

(a) Thegaging tolerances andallowancesshaObe in accordance with the applicablevalues found in table II.

(h) American Gage Design standard blank.shall be used wherever possible.

(c) Thethickness of section shall bekeptuni-form to prevent deformation in heat treat-ing and, further, the depth of cross-section shall be sufficient to prevent thegaging dimaeter from going out-of-roundin excess of the tolerance allowed.

3.3.1.2.1 Plain Skp Ring Gages. A step ringgage is a plain ring which has a surface groundperpendicular to its axis for use in gaging a length.The specification for the cylindrical gaging featuresshall be identical to that for a standard type gage.The following should be considered when desigtliug agage of this type:

(a) Tbering shaOhave achamfertocleartbeallowable fillet on the part.

(b) The step surface on the gage shall he im-mediately adjacent to the part surfaceand shall be accessible for feel purposesor for use with’a straight edge,

(c) Theparttolerance should be.0050rgreatersince theaccum.cy of inspection dependson feel.

(d) Clearance cutsorslots shal]beincorporatedin the design to clear obstructions.

3.3.2 TAPER RING GAGES, Taper ringgages are used for checking the various dimensionallimits of tapered parts such as diameter, Iengtb,angle, or taper. When gaging tapered parts, thedesigner shall take care to sufficiently control allpart dimensions, In some instances, it may benecessary to use a female taper flush pin gage inconjunction with a plain taper ring.

3.3.2.1 Where practical, taper ring gages shaUhedesigned so that American Gage Design standardblanks may be used.

3.3.2.2 Thecontrol ofti.sdiameter of thetaperedprotrusion on the part is usually a: fained by grinding

stepson one end of the ring wk;dt indicate the limitsof thedistancet.he gage may fit.ol]toa!] acceptablepart. When it is necessary to determimt the limitsof the taper or the angle, two (2) taper rings areemployed. One ring is made to the maximum mgleand the other is made to themiuimum angle, andare employed similar to the taper plugs of para.3.2.4.1.

AGO 101I7A 53


MILnHDBK-204

,3.3.2.3 Preference shall be given. to the datumdiameter system of dimensioning in conjunctionwith the uac of a basic taper, if the length of taperis~nmh’ that th:, taper is sufficiently controlled bythe tolerance zone created. when the length ofthetaperiscbort, atolerance onthetaper or angleis generally required,

3.3.2.4 Taper rings usually are fittcdto a Mastertaper plug by the blueing transfer method.

3.3.2.5 Wear allowance shall not be applied ontaper gages for tapers over 15” included angle asthere is a minimum of sliding contact, A chamferat the large end of the ring is not necessary sincetaper parts are easily inserted into the gage.

3.4 SNAP GAGES. A snap gage consists of

opposing measuring surfaces separated by a spaceror frame and is used for gaging diameters, lengths,and thicknesses. A snap gage is an excellent NotGogagesinceovality below theminimum limit caneasily be detected. A snap gage is an adequate Gogage for many purposes; however, a ring gage ispreferred if aasmnbly is the prime consideration.There are three general classes of snap gages:adjustable, (ixed,an dindicating.

3.4.1 PLAIN ADJUSTABLES NAP GAGES.Plain adjustable map gages with or without extendedanvils are used for gaging part diameters, thicknessesand lengths when the part tolerance is .003 or greater.Gages of this type are classified as Mil-Std gagesand accordingly no drawings are required. Mil–Std-~18 gives a listing of stock numbers for unsetplain adjustable snap gages (plain or extendedanvils, square or round button type) for size rangefrom 0toll,625 inches. This Mil-Std catalog also

establishes the method for listing the proper stocknumber and setting size on the Lkt of InspectionEquipment.

3.4.1.1 Adjustable Snap Gage-Modijicd Anvils.SWcial part features often require that the snapgage anvils must be modfied to a special form.Particulm attentinn shall be given to insure thatthe upper and lower anvils be held withh the properalignment to insure correct functioning of the gage.It is also, necessary to check the location of thescrews in the lower anvil to insure that no inter-ference will occur between the required contour oftbe anvil and the screws. The proper alignmentnotes between the upper and lower anvils droll bespecified as well as the detailed dimensions ?f themo@ied anvils. Mil–Std-l 18 presents a method

for classifying a modified adjustable snap gage as astandard gage. This method, however, shall beused only in the event that the modified anvils maybs umd for inspecting a series of similar dimensions.(Example: thickness of wall at mouth on cartridgecase%) Generally, when a modified anvil is requiredthe modification is such that the likelihood of furtheruse on other parts is improbable and thereforq a

gage drawing must be prepared depicting the re-quired modification. The setting size in this case

sbali be specified on the gage drawing and not on theList of Inspection Equipment, The gage drawingshall then be classified as Special.

3.4.1.2 Adjustable Snap Gage-Blade T.vpc A nuil.Thk type gage is a standard commercial product.The gage consists of a C frame on which are mounted

adjustable blade anvils, The thickness of standardanvils is either .130 nr .183 inches. These thinblades arc particularly adaptable for gaging recesseddiameters in shafts, the recescss posccaaing dimeri-sional limits or shapes for which an ordinary ad-justable snap gage would not function. B1ades ofspecial th]ckpesses and forms may be designed tosuit specific requirements. In designing gages of thistype, the proper frame for the~iven part dlametef mustbe selected and the width and contour of the bladeanvils chall be specified or detailed in the eventthat the anvils deviate from the standard type.Thk type gage should not be used for part tolerancesof less than .003.

3.4.2 BUILT-UP SNAP GAGES. Build-upsnap gages are used primarily where a fixed typegage is desired and the part tolerance is about .003.Built-up snap gages are also widely used for largerpart tolerances where the part shape is such that astandard or extended anvil type adjustable snapcannot be uced. The us-c of built-up snaps shouldbe minimized on low production items.

3.4.2.1 General Construction Feaito’es. A built-upsnap gage usually consists of two hardened steelanvils separated by a soft steel or cast iron spacer,the three pieces being fastened together with sockethead screws of a size proportional to the size of thegage. When the gaging dimension is above one

inch, the anvils shall be fastened by screws enteringfrom each anvil. Tbe length and width specifica-tions for the anvils Jmll, be governed by tbe partsizes. The spacer is made from soft machine steel,as this is an aid in maintaining dimensional stability.However, gray cast iron spacers have been recentlyintroduced and due to the even higher degree of

54 AGO 10117A


dimensional stability, this type of spacer’ is pre-ferred,

3.4.2.1.1 Built-up snap gages may be of the singleend, progressive, or double end type design. Theprogressive type is considered the most desirable

from a standpoint of rapid inspection. Hnwever,there are certain instances where the part designis such that a double end type becnmes a necessity.

3.4.2.1.2 The Go end of a built-up snap gage shallbe identified by a radius on the anvil and the Not Gnend shall be identified by a chamfer

3.4.2.2 Built-up Snap Gages-Separate ReceiuerType, It is often necessary to design a receiver orholder for the part which is used in connection witha built-up snap for gaging length from a datum or ataper, position of shoulder, etc. The receiver isusually designed to slide on the bottom anvil andthe limits are established by progressive stepson theupper anvil.

3.4.2 .2.1 Receivers nf the female tvDe usuallv. . . .. . ...- .require a check gage which simulates the criticalform and dimensions of the part. The check gageshall be depicted on a separate drawing.

3.4.2.3 Built-up Snap Gage.s-Rece.ssedAnvil Type.It is nften necessary to provide recesses or cavities inthe anvils nf snap gages to clear protrusions o“ or inthe part gaged. The designer shall take specialcare tn provide clearance at extreme conditions byproviding the required chamfers, etc. If possible,sufficient clearance shall be provided so that keysand dowels arc not required to maintain alignment,

3.4.2.3.1 Where alignment of the part is to becontrolled or is a factor in the gaging of umtherfeature, the upper and lower anvils sb.all bc keyed ordoweled to the spacer. A nnte slid .-ppear on thedrawing specifying the misalignment allowed on theassembled gage,

3.4.2.4 Built-up Snap Gages-Relieued Anoil Type,Where the part gaged has a small cnntact surface, itis advisable tn reduce the width nf anvil to a practicalwidth on which approximately even wear will occur.It is d]fficult to pick up a small area nf wear in ~wide anvil a“d this leads to errors in gage mrveil.lance since a gage blnck measurement will begoverned by the high points or unwnm surfaces onthe anvils.

3.4.2.5 Carbide inserts may be used on the anvilsof built-up snap gages to minimize the effect of wear,The use of inserts is recommended particularly onstandardized items where production is high and the

AGO 10117A

MIL-HDBK-204

component design or material is such as to causerapid wear nn the gage.

3.4.3 PLATE GAGES OF THE SNAP TYPE.This type of gage is not easily salvaged and should

be employed only where an adjustable snap orbuilt-up type is not adaptable to the particularapplication, It is made entirely from one pieceof steel which is hardened and finish ground tosize. A chamfer on the outer corner of the anvildenotes the Not Gn gaging side while a radiussimilarly placed identifies the Go side on the doubleend type. Gages of this type require wear allowance.

3.5 TEMPLATE GAGES. Template gages arewidely used to check profiles, lengths, widths anddepths. Gages of this type are economical tomanufacture due to their simplicity. In the case ofprofile gages and certain length types, the gage issimply a measuring stick, and acceptance of tbepart depends upon the accuracy of the inspectnr’svisual judgment. When gaging complicated pro-files, it is suggested that an optical comparator beused in lieu of a template type, particularly if thepart is used nn a standarditem.

3.5.1 GENERAL CONSTRUCTION. Templategages of tbe small and medium types are usuallymade from hardened tool steel ~to3/s inches thick,the gaging surfaces being ground to the proper size.In snme cases, large gages are made from machinesteel, the gaging surfaces being case-hardened andground to size. (Generallyj gages are designed topermit the manufacturer to use construction holestn facilitate gang milling and grinding so that severalmay be made in one set-up. )

3.5.2 TEMPLATE GAGES FOR DEPTHS &LENGTHS. This type of gage usually resemblesthe letter T in shape, the gaging surfaces being theundersides of the cross bar of the T which are groundparallel and in line, Parallel to these surfaces, twosteps separated by an undercut, are ground on thebase of the T their difference being equal to the parttolerance. Template gages for depth and lengthdo not require wear allowance.

3.5.2.1 When a part has a tolerance of .03 orgreater, it is sometimes feasible tn use scribe linesto denote the maximum and minimum lengths.This type gage is usually L shaped and is faster inoperation but less accurate. Scribe lines shall be.005 maximum wide by .008 maximum deep andshnuld be placed on both sides nf the gage.

3.5.3 TEMPLATE GAGES FOR PROFILES.This type of gage is used to inspect various profiles

55


MlL;HDBKy2~.. ’.’.and contours. It, is made .of hardened tool steelground to the’proper profile, Generally, the gage ismade to” the muiimunr profile while scribe lines arepositioned to indicate the minimum conditions oflength. The profile or gaging surface should bechamfered on both sides to produce a thin sightingsurface, the desired thickness of the gaging surfaceranging from )f’Zto ~~ inch.

3.5.3.1 Profile gages may also be designed using anominal profile and in this ce e an acceptable

contour is determined’ simply by vsiual comparison.This type of design should he used only on partswhere the contour is of minor iDportarrce. In

other instances where the contour is relativelyimportant, maximum and minimum profile gagesshould be employed to insure that the contour iswitbin the desired limit.

3.5.3.1.1 Tolerance on angles should equal 10percent of the angular tolerance on the part, wppliedminus on max and plus on min. Tolerance on rad]ishould equal 10 percent of part tolerance. Where notolerance is shown on angles or radii on the partdrawings, the tolerance on the gage will be dependenton function of the parts. Where there is no fit,tolerance on angle will be +0”5’ and on radii +5percent of radius,

3.5.3.2 Profile gages generally require an accept-ance check gage, The gage is fitted to the checkand is acceptable when the viewing on a comparator.

shows perfect matching of the profiles. Only oneacceptance check ii required for each lot of gages.

3.5.3.3 Since profile gages rely on the inspector’svisual accuracy in sighting an acceptable contour,they should be used sparingly on complica~d pro-files. On standardized items, preference should begiven to the use of optical projectors in order tofacilitate accurate inspection.

3.6 FLUSH PIN GAGES. A flush pin gage isdefined as one which utilizes a pin that protrudes oris recessed a known length, movi,ng in relation to areference surface to indicate acceptabllit y.

3.6.1 APPLICATIONS. Flush Pin gages areused for checking dimensional features swh as thefollowing:

(6) Depth of hnles, either .straight or tapered.(b) Height of bowes, either straight or tapered,(c) Location and position of holes, bosses, etc.(d) Perpendicularit~,

The application of f-lushpin gages is generally con-

fined to the gaging of dimensions having a toleranceof ,005 or greater. When the part tolerance is

under .IX15,it is preferable to use a dial indicatortype gage rather than to rely on the accuracy of theinspector’s sense of touch.

3.6.2 GENERAL CONSTRUCTION FEA-TURES. The common type of flush pin consistsof a body, mnvable gaging pin and pin-retainingdevice. There exists a multiplicity of body stylesand retaining devices currently in use. In theinterests of standardization, however, the followingconstruction criteria are preferred.

3.6.2.1 Barrel Type Flush Pin. These gages areso named because the body is cylindrical in shape.The basic design criteria are:

(a) A cylindrical body having a minimum wallthickness of we inch, knurled and withtwo flats, diametrically opposed, pro-vided fnr marking purposes.

(b) A ratio of length of body to diameter ofsliding pin of about 3:1 (3:1 plus com-ponent dimension for internal gages).

(c) A retaining device consisting of a button-head socket screw, located ~ inch from

the top face of the body and having thefimt ~ inch of its length machined downto the minor diameter,

3.6.2.2 Bar Type Flush Pin Gages. These gagesconsists of a pin sliding in a bar. The pin may becentered in the bar nr placed in any position alongthe bar. The bar should be basically rectangular inshape with recesses along the sides for easy gripping.

3.6.2 GENERA L DESIGN CRITERIA. Thefollowing precautions shall be considered whendesigning flush pin gages:

(a) Tbe end of the pin or bottom of the hole inthe body shall be chamfered wherevernecessary to clear any chamfer or filleton the part feature.

(b) The diameter of the pin for external flushpins or d]ameter of the hole in the bodyfor internal flush pins shall always clearthe worst condition relative to the dia-meter of the part.

(c) All feel surfaces must be easily accessibleto the inspector when using the gage.

(d) All feeler edges (both steps on body andtop edge of pin) shall be sharp to insuregaging accuracy. A note to thk effectshall appear on the drawing.

(e) The movement of the flush pin shall besufficient to insure that the part can

56 AGO 10117A


always be applied to the gage and easilywithdrawn after gaging.

3.4.6 EXTERNAL FLUSH PIN GAGES.This type of flush pin is used to gage the depth ofholes, or similar female dimensions. It consistsof the body together with a protruding pin thatenters the feature being gaged, The other end ofthe pin is correlated with the reference stepson thebody to indicate whether the, part dimension lieswithin the desired. limits,

3.6.4.1 Flush Pin Gages Entering Thread Cavities.When a, flush pin gage is used to measure the depthof a threaded cavity, the pin, must clear the minordiameter. The pin diameter shall be dimensionedto either 40~o of the difference between the minordiameter of the part and the mating part, or ,002whichever is the larger, In the event that themating part is designed with a pilot extending intothe threaded cavity, the flusy pin shall have aeimilar pilot based on the conventional 40~o func-tional rule.

3.6.4.2 Foush Pin Gages for Depth of DrilledHoles. The depth of drilled holes isusuallyd]men-sioned from the entered surface to the intersectionof the cylindrical surface and the drill angle. Un-fortunately, drill wear usually creates a varyingradius atthk intersection. Therefore, fluih pins forthe depth of drilled holes shall be designed to clearthk rad]us and contact the conical surface belowthe intersection. This isdoneby grinding a smallerdiameter on the end of the flush pin, maintaining

a sharp corner at the bnttnm. In dlmensinning,an amount equal to the additional length from thepoint of the intersecting of the part to the point nfcontact nf the flat bottom flush pin, is added tn thegaging eizes. See figure 19,

3.6.4.2.1 Since the gage presents only line contact,it ~ advisable to, ,uee carbide insetis ~11the bottnmof the pin in nrder to maintain sharp edges.

3.6.5 INTERNAL FLUSH PIN GAGES. Thistype of flush pin is used to gage the height of a bossor other type of pintrueion. The gage is designedas above, except. that the length of the body isthree times the pin diameter, plus the part dimen-sion. For gaging part dimensions up to ~ inch, aslot should be cut in the side of the body to permitviewing the contact between part and pin. Above

% inch, a hole shnuld be drilled through tbe bndyto permit viewing the same. The lower edges nf thereceiving hnle are chamfered to clear any fillets at thebase of the protrusion.

MiL-HDBK-204

3.6.6 TAPER FLUSH PIN GA GES., Thistype of flush pin is generally used h gate the dis-tance from a surface to a datum diameter in atapered hole or on a cylindrical tapered bnss. Thedesign” features of thk type of gage are identicalto those mentioned in paragraphs 3.6.4 and 3,6.5,except that the slicbg pin or the body, as the casemay be, is tapered’ to suit the taper of the hoie orboss. The gaging dimensions are given from thebase of the body io the datum diameter on the pin orfrom a datum on the body to the end of the pin.Wherever practical, the gage taper should be di-mensioned simihm to the part taper and care shouldbe taken to insure that all component variationshave been considered. The tolerance nn the taper

part of the pin or body should be taken in the properd]rection to slightly clear tbe worst possibli conditionof the part. When gaging snme types nf taper holes,it is necessary to use a two section taper flush pin inconjunction with a plain taper plug gage to suffi-ciently control all of the component variations.

3.6.7 SPRING LOADED TYPE FLUSH PINGAGES. The use of spring lnaded pins eliminatesthe need fnr the inspector to seat the pin ,befnrefeeling the steps. Spring loaded types should beused primarily on those fixture gages where the num-ber of gaging elements may make it impractical forthe nperator to seat each pin befnre feeling the steps.

3.6.8 MULTIPLE TYPE FLUSH PINGAGES. When a part is designed with a counter-bore or a protrusion having two different d]ameters,it is snme:.imes desirable to check the depths orheights simultaneously. In this instance, a multipleflush pin g$ge is employed. The design features.ofthis type of gage are similar to the ordinary flush pinexcept that there is an inner pin sliding within theouter slidlng pin and the bottnm of this outer slidingpin acts as the gaging surface from which the innerpin measures. There are twn sets of steps, one set onthe body for the outer pin, and the other set on the

inner pin. See figure 20.

3.6.8.1 On occasion, it is necessary to employ themultiple flush pin nn tapered holes or protrusionswhere all the part variations cannot be gaged usingthe nrdinary type of taper flush pin or plug. ~~

3.6.8.2 Multiple flush pin gages are relativelypensive and their use should be confined to stan-dardized items of high production or employedonly when the part design precludes the use ofordinary flush pin gages.

AGO 10117A 57


Ml~HDBK-2M

.?TL.:~US&T2M TASLE I

2 REF

..—.

J

“g”~---——— —----

A <$4-1

SHARP

d---

)= MIN DIA. = MIN DEPTH- = TOLt = TOLI = .01 )

ANC#T@=~RNl

D+t

t {PART

FLUSH PIN FORMULA

FOR DRILLED HOLES

FOR 118”DRILL

@= D-.002

@= D-.97R

@,= .8837 (@-@

@= L+.2914R

@=@+ T+.3004t

, @=@-@

fl = .25A = 29”30’

OTHER ANGLES

@- D-.002

~= D-2[1-cc5*)R

a=%@= L+(SIN~-TN $)R

@@+T+~

O-Q-O 7# - .25A

FIGURE 19. Flush pin formula for d,ifkd holes.

58 AGO 10,,7,4


MIL-HDBK-204

‘\ PININNERPIN

Fzonm 20. Multiple jlu8h pin.

3.6.9 BUILT-UP TYPE FLUSH PIN GAGES.Some part designs necessitate the use of complexflush pin gages t? measure various lengths, depths,thicknesses and locations, One or more flush pinunits similar in principle to standard flush pingages are mounted on a frame or case along withpositioning and holdlng devices to comprise thecomplete gage. Designs of this particular typeare difficult to standardize; therefore, their develop-ment depends upon the part design and the gatedesigner’s originality.

3.7 SPANNER GAGES. The term “spannergages” as used in the following paragraphs refers togages which are designed to check either the locationof p~ln or threaded holes or protrusions or thespacing of slots.

3.7.1 GENERAL DESIGN DATA The firststep in the design of spanner gages is to determinethe mating part conditions. The survey must ascer-tain if the extreme part limit conditions permitproper assembly. The designer must then decidewhether to gage the actual or the implied dimensions,particularly with the two pin or two hole type.

3.7.2 TWO PIN (HOLE) GAGES. The sim-plest type of spanner gage involves either two pins or

two holes or a combination accurately located withrespect to each other. The design data is asfollows.

3.7.2.1 The distance between centers of the holesor pins on the gage shall be equivalent to the meanof the part hole or pin spacing. The tolerance onthis distance shall be five percent of the part spacingtolerance applied, bilaterally (+ .05YO). It shallnot exceed +.0005 or he less than +.0001 in any

case.3.7.2.2 On a male type gage, the diameter of each

of the pins shall be equal to the minimum diameterof the part hole minus one-half of the total toleranceon the part hole spacing. The toleranoe on the pin

diameters shall be the “go” tolerance from Table H

applied PhM. The part tolerance on the holes shallbe used to obtain the required gage tolerance fromthe tolerance table.

3.7.2.3 In the female type gage, the diameters of

the holes shall be equal to the maximum diameter ofthe part protrvsiom plus one-half of the totaltolerance on the part spacing. The tolerance onthe hole diameters shall be the Go tolerance fromTable H, applied minus, The part tolerance on thepin shall be used to obtain the required” gage toler-ance fmm the table.

3.7.2.4 When a location of a hole or protrusion isgiven from a surface, the total part spacing toleranceshall be added to the gage hole or subtracted fromthe gaging pin diameter. Tolerance applied sameas above.

3.7.2.5 Generally, where only two holes or pro-

trusior~ are concerned, sufficient information forgaging is given hy the distance between holes andtolerance on holes being specified. However, if thetolerance has been omitted or available tolerance isnot sufficient, the gage may be designed using im-plied dkensions.

3.7.3 MULTIPLE PIN OR HOLE ‘GAGES.Multiple pin or hole gages are designed utilizingthe same basic data as two pin gages. That is, thatthe ideal center of the part pin or hole coincideswith the ideal center of the gage pin or bole and thegage pin or hole is altered by the amount of disloca-tion to allow acceptance of any correct diameter pinwithin the area defined by the locational tolerance.

3.7.3.1 However, in dimensioning this type ofgage, difficulties arise. A careful survey of the partdimensioning and tolerancing and that of its matingpart must be made. If the part has been dimen-sioned using the baaic location system with a loca-

AGO 10117A 59


MIL-HDBK-204.,,

tional tolerance according to MIL-STD-8, it is arelatively simple matter to gage if the part tolerancesarc not extreme. It is recommended that coordinatelocation he used despite the increase in accuracyrequired of the gage.

c.7.4 BASIC CONSTRUCTION

3.7.4.1 Mak Spanner ”Gages. This gage consists.of a holder inta which the gaging pins are secured.The holder is usually of soft machine steel to facili-tatethe.precision location needed for the pins. Thepins are usually driven in the holder, and mayor maynot be shouldered. The, holder will contain knock-out holes for removing tbe. pins. The pins shouldbe designed with chamfers to aid in entering the part.The length of the pins may vary according to thedicta~es of theindividual part. However, whmnototherwise limited by the part, a length equal to oneand one half times the diameter of the pin is con-sidered good practice.

,3.7.4.2 Female Spanner Gages.. This gage con-sists of a.plate and the necessary busbings to gagethe protrusions of the part. The plate is usuallymade from soft machine steel:ta facilitate the pre-cision location required for the bushings. Theinternal diameter of the bushings is ground con-centric with the outside diameter. and press fittedinto the piate. The bushings are made from har-dened tool steel and may either be”of the headlessor head type. It is advisable, wherever possible,tousestandard commercial bushings. Their lengthwill determine the thickness of the plate. Tbebushings will he chamfered to clear any part filletor radii.

3.8 CALIPER GAGES. Caliper gages are anygages with movable arms (or a combination offixed and movable arms) that transfer a part featureinserted between or placed over them toanindicat-ing mechanism.

3.8.1 DESIGN .CONSIDERATIONS. Themajor considerations in the design of caliper gagesare the rigidity of the arms, the aligriment”of thecalipering points with each other and with the sur-face to he gaged, the accuracy of the pivot andfinally the relationship’ between the lengths of thegaging arms and those of the indicating arms.

3.9 COMPARATOR GAGES. A comparatorgagehasbeendefined asany gage which utilizes tinindicating device to directly contact tbe work andindicate its departure from a preset size with aminimum of auxiliiry devices,

3.9.1 CONSTRUCTION. As illustrated, most

comparators consist of a sturdy base and column,together with an arm riding on the column carryingtheindicating device orits sensing element. lIMherthe top surface of the base is finished square with theindicating device or an anvil with a lapped uppersurface is provided. The anvil is usually serratedto reduce the amount of surface to be lapped andresistance to sliding motion of the part. Theindicating device used on the comparators may beair, electric, mechanical, or optical. An opticalprojector is not classed as a comparator. Seefigure 21.

3.10 RECEIVER GAGES. Receiver gages areprecisely what the name implies. They receivethepart andverify its dimensions. The name shallbe applied mly to gages which consist predominantlyof internal surfaces or portions of surfaces arrangedto verify “part dimensions. Gages consisting of ex-clusively external surfaces are dealt with underparagraph 3.2,6, Multi-Element Plug Gages.

3.10.1 APPLICATION. This type of gage isused primarily to inspect the interrelationship oftwoormore external surfaces. It maybe designedon the basis of either dependent requirements speci-fied on the part drawing or independent require-ments which cannot be gaged economically bydirect indication.

3.10.2 DESIGN CONSIDERATIOAIS. Eachsurface of the gage is designed using the maximumsize of its corresponding part surface plus theallowable misalignment per individual surface. Ingages with only two gaging surfaces which are alsoadjacent, half of the allowable misalignment may beadded to each maximum part dimensions. If thereare more than two gaging surfacesof if the surfacesare not adjacent, then one surface is held to themaximum size of its corresponding part surface andall the allowable misalignment added to the maxi-mum size of theothcr surface. Wben thus designed,the gage will insure that the parts are within thespecified limits of alignment when the individualpart sizes are maximum. (Max metal condition)

~3.10.3 GENERAL CONSTRUCTION. Czagescontaining only two shallow gaging diameters shouldutilize American Gage Design Standard solid ringgage blanks, if possible. Gages with more than twosurfaces or long gaging surfaces may be manufac-tured in one piece if they arc not too large, but pref-erably should be constructed in sections that arcprecisely fitted into a holder unit. Sectional con-

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,,,.

I

! AGo 10117A

FIeunE21. Cumpamto,gagea.

61

!, ..;...’...,,


MIL-HDBK-204

struction, facilitates manufacture, inspection, sur-veillance, andrepair or modification. Caution mustbe exercised to maintain reasonable uniformity ofsection throughout the design of both solid andssctional type receiver gages to prevent distortionduring heat treating.

3.10.4 CHECK GAGES. The problem. of ac-ceptance and subsequent surveillance inspection ofreceiver type gages must be considered. A checkplug shold be designed for 811 gages which cannotbe conveniently xetup for measurement.

3.10.4.1 The check plug shall be shown on a

separate drawing. Thegage shall be marked “AC-CEPTANCE CHECK FOR 7XXXXXX2”. Therequired gage sizes will bechown on the elementaoftbe check plug. Tbering can reaccepted as beingdimensionally correct ifit fits the check when in-spected with the Pmssian Blue transfer procexc.

3.10.4.2 Insomeinstances, smaller receiver gagescan be designed to eliminate the use ofa cbeck pluggage. Thm is accomplished by finish grinding theoutside diameter and then finishing the insidediameters concentric with it. Using theuutsidediameter as a reference surface on whlcb the gagemay be rotated, the gage checker can measure theinside dlametem and verify their concentricity byuse of a dia[ indicator.

3.11 FIXTURE GAGES. Any gage consistingpredominantly of devices arranged to verify thefeatures of a part shall be labeled a fixture gage.

3.11.1 GENERAL CONSTRUCTION. Fixturegsgcs vary in type and method of constructiondependipg upon the nature of the part, the functionor functions being checked, and the gage designer’soriginality. Generally, fixture gages usually con-sistof the following pa~tsor elements:(a) abase, (b)locating pins, bloiks, clamps, (c) indicating devices,ilrish pins or dial indicators, (d) necessary part hand-ling aids for the inspector such as positioning orejecting. devices.

3.11.1.1 Some types of fixture gages, require theuse of numtersfo rsettingof the gage prior to check-ing a group of park Tbie setting master usuallysimulates the, part but is not necessarily an exactduplicate of tbe part.

3.11.1.2 Gages should be designed to hold thepart or locate it in a manner assiniihm to its func-tionallocation or function aapossible. Inaddltion,fixture gages should be desigued t6 check the part inaccordance with tbe dknensional specifications ratherthan totbeparticrdar method of manufacture. Care

should be taken in analyzing the parts to be gaged sothat the correct locatipg and beddkig points will hechosen.

3.11.1.3 Whers close dimensional limits must bemaintained, welded construction should be used withcaution.

3.11.2 ECONOMY IN MANUFACTURE. Afixture gage is a specialized type of gage whichusually is applied to only one part. Its size and

dimensional accuracy is such that tbc cost of thegage is usually rather expensive, Therefore, thefollowing points should be considered to effect the

greatest economy.3.11.2.1 The part being gaged should be a stan-

dardized item warranting the design of a complicatedfixture gage.

3.11.2.2 An investigation should be made toassure that a commercial gage is not available whlcbcould be modified to suit tbc given part at a reason-able cost.

3.11.2.3 When a fixture gage is designed, the costof the gage should be amortized in a saving of in-

spection time. Therefore, tbe designer must designa gage that is easy to operate incorporating quickoperating and positive gaging features.

3.11.2.4 When a fixture gage is needed to gate anexperimental item, the designer should, if possible,provide an improvised method of inspection usingstandard measuring equipment> with oue or two

specially made adapters to facilitate positioning orlocating, if necessary.3.11.3 OPERA TING MECHANISMS. The

gage designer may minimize the part inspection timeby employing any of the following basic mccbanisms:

(a) Quick acting cams for locating or locking.(b) Spring loaded pins and plungers.(c) Multiple lead screws.(d) Levers(e) Hydraulic or air cylinders for lifting or

moving the part into position.

3.11.4 R.EPLACL!WENT ELMJiW TS. In de-signing fixture gages, an analysis most be made of thedifferent gaging elements to ascertain which parti-cular parts are subject to wear and wi[[ c>,entua[lyneed replacement. The gage must be designed sothat thecs parts can be easily replaced, involving aminimum amount of time and expense without de-stroying the required accumc y of the gage. Threadplugs and thread rings used on fixture gages areexcellent examples and provisions must be made fortheir replacement. In some isolated cases, one

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fixture gage may be designed to suit two or moresimilar parts by the use of replaceable or inbr-changeable elements, (See paragraph 2.3.4.)

3.12 INDICATING TYPE GAGES.3.12.1 APPLICATION. Most types of basic

gagw such m snaps, flush pins, length gages, etc.,can be designed using indicators inctead of fixedanvils or profiles. This conversion in design icpreferred under the following conditions:

(a)

(b)

When the part tolerance is relatively small(under .005) and the specific type gageutihzes feel or sight, an indicator canoften be mbstituted to improve accuracy,

On low production or expwimental itcmc,indicating type gages may be used to injspect several parts having similar di-mensions which fall within the range ofthe indicator, thereby elimhmting theneed for several fixed gages,

3.12.2 TYPES OF INDICATORS. There arevarious indicating type gages available commercially.The moct common arc mechanical dial indicatorsand air-prccsure activated indicators.

3.12.2.1 Mechanical Dial Indicators. Mechani-cal dial indicator have been st,andard,z~ with re-spect to range, accuracy and mounting dimensions.The pertinent information may be found in MILI-18422.

3.12.2.1.1 The range of the indkatnr shall ex-ceed the component tolerance and also be suffi-ciently large to enable ecsy entry and removal ofcomponents from the gage.

3.12.2.1.2 The graduations on the dial shall besuch that ample circumferential spacing exists be-tween the maximum and minimum limiti. A goodempirical rule is that the range of the indicator bc

appmfia~ly eight (8) times the componenttmlerance,

3.12.2.1.3 The proper type of indicator back shallbe selected to facihtate simple and economicalmounting of the indicator and provide the desiredadjustment in positioning. “Back” type mountingsare preferred to “stem” mountings, since irnpropcrclamping may bind the spindle.

3.12.2.L4 When applying indicators to heavy orcumbersome components, it is advicable to applysome intermediate gaging device to act as a shockabsorber. Guards around the indicator ta preventdamage me also adviaable.

3.12.2.1.5 When designing gages utilizing mechan-ical ,dial indicators, it shall be kept in mind that

there are considerable variatiorm in ,various commer-

cial indicators that nevertheless meet all AGDspecifications. If the specific application will onlyaccept a certain indicator, it shall be so specifiedon tbe drawing. Thk condition shall be avoided wmuch as pocsible.

3.12.2.2” Air Pressure Indicators. There ar,e twogeneral types of air pressure indicator, differingprimarily in the method of indication. Both usethe flow characteristics of air through orifices.However, one method uses a float suspended in atapered tube to indicate the relative velocity andthus the comparative size, while the ether uses adifferential bellows, bourdon tupe or other mechaui.cal sensing device to indicate on a dial similar to thatof a mecbanictd dial iI]dlcator. Tbe float and

differential types appear of equal merit. Tbe flow(or tube) utilizes two matters (not necessarily the

part limits), one to set the zero set, the other toestablish the magnification. The differential typebuc a fixed magnification and may be set with asingle master, See figure 22.

3.12.3 Setting .kfcmters, Setting mutters for simpledimensions may be plugc, rings or set master disksus shown in Commercial Standard CS8, Gage Blanks.The form of the setting master should approximate

Fmtm. 22. D@ and column type air presww indicalom.

AGO 101L?A 63


~11:HDBK_2&

the form of the piece. beirig @stiected. It ii Pref;erable that. both a maximum an!f mi?imum masterbe used for each application. The indicator is setto ope limit and the othe! limit checked ~ PrOveout the magnification. Inaccuracies of magnifica-

tion can be compensated for by ruling new lines onthe dial face.

3.12.3.1 Except for very tight tolerances ,Or anextremely critical limit, it is not neces~ry tO specifymasters fo; the exact tolerance limitq, the nearestthousandth generally being .satisfactOrY Further,the toleraricing of such set masters should be

,,,

,.,

,,

., .,.

,. .,

bhteral, so they IIIay be used fOr a limit in eitherdirection, high or low. The tolerance. should behalf the Master tolerance from Table II appliedbilaterally. Furthermore, since masters generallyhave their exact si~es recorded in acceptance orcalibration, the indicator can be set to this size,thus giving a high order of accuracy regardless of thedirection of tolerance or its magnitude.

3.12.3.2 In cases of a liberal tolerance or a Maxor Min limit, a single master may be used to set thedesired limit at zero and the accuracy of the indicatormechanism is used to establisb the limits of tolerance.

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CHAPTER 4. INTERRUPTED DIAMETERS.4.1 INTRODUCTION. Thk section contains the

pertinent design data for interrupted diameters suchas threads, serrations and splines. ,.

4.1.1 GENERAL Broadly speaking, gages forinterrupted d]ameters are gages to insure inter-changeability. Usually, a multi-element “Go” gagethat simulates the mating part determines if the partbeing inspected will assemble with any acceptablematirig part, and one or more single element “iNotGo” gages check critical dimensions (such as pitchdiameter) to insure that they ime within acceptablelimits.

4.2 UNIFIED AND AlilERICAN NATIONALTHREADS.

4.2.1 GENERA’L. Thetwcimost common tbread

forms are the 60° Unified form that has been de-veloped as._an international standard and theAmeric~”’Nitional form.

4.2.1.1 Standardization. Duetothe wide applica-tion of the basic thread form the gages have reacheda high degree of standardization. The specificseries—UNC, UNF, UNEF, sUN, 12UN, and 16UNhave been cataloged as Military Standards. Thedesign data for gages for threads of special diameters,pitches and lengths of engagement has also beenstandardized and is presented in Handbook H28,A discussion of the gaging approach and policy iscontained in this section.

4.2.2 GAGES FOR INTERNAL THREADS,

4.2.2 .lGo Thread P@Gages. AGo thread plugis designed to check the minimum pitch diameter,the clearance at the major diameter, the lead, andthe flank angle all simultaneously. When aGo gageenters the part, assembly of the inspected threadwith any acceptable external thrsad is assured withonly the minor d]ameter of the part requiring furtherinspection.4.2.2.1.1 Go Thread Plug Gages for thread sizes

.150 or below shall have themaleprecisi,on centersleft onthegaging members. Onali Gothread plugswith a nominal thread size above .150, a slot calleda ch}p groove shall be cut through the first three orfour threads attbeentering endofthepl”g, Othertype chip grooves’ in” accordance with commercialpracticesuch as the longitudhlgroove extendingthe complete length of the gaging member wiO beconsidered as acceptahIe. This shall apply to allmale threaded gages including those used tu gageconcentricity, alignment, and ‘similar functions.

The slot shall be cut parallel to the axis of the threadand shall in all cases extend below the root of thethread. The preferred dimensions for the width,depth, etc., will be found in MIIATD 114. One

chip groove is required at the front end of the gagingmumber, unless the gaging member is reversiblewhich requires a chip groove at each end.

This slot is to serve as a reservoir for coilectj”gforeign matter that might damage the thread flanks.It is definitely not intended to function as a tap forcleaning out burred threads.

4.2.2.1.2 On gages without “a chip groove thepartial thread at the front end of the gaging membershall he removed to a blunt start to avoid featheredges. On gages with a chip groove, the partialthread preceding the chip groove sbaO be completelyremoved to a dept~t. least equal to the minordiameter of the thread. Not more than one com-plete turn of tbe thread shall be removed to thepoint where the full.thread form is obtained. Ongages of 28 threads per inch and finer, a 60” chamferfrom the axis of the gage is permitted in lieu of re-moval of the partial thread. Gages that have maleprecision centers left on the gaging members performthe same function as the 60” chamfer.

4.2.2.2 Not Go Thread Plug. A N’ot Go threadplug is designed to check only one element of thethread, the pitch diameter. The thread form onthe gage is truncated at the crest and cleared at theroot so that the flank makes contact on a limitedarea of the part thread flank. This is to determineif the pitch diameter has exceeded the maximumlimit.

4.2.2.3 The conventional method of inspecting the

limits of the minor diameter of an internal threadutilizes plain plug gages. A Go plug gage insuresagainst undersize minor diameters and the Not Goplug insures that there is sufficient depth of thread.

4.2.2.4 Depth Requirements. A large percentageof part tapped hole specifications include a require-ment for minimum length or depth of full formthread. Occasionally, a maximum Iengtb of fullform thread is confused with the’specification’ fordepth oftapdrill or bore diameter. Thedepthsball

betonsidered to betothe cent.erlineof a full formthread space on the part internal thread unless other-wice specified.

4.2.2.4.1 Theconventional method of gaging tbisdepth is with a step or flat added to the Go thread

I

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MIL-HDBK-2~

pluggage. Onapplicationswhere morethan twenty-five percent of the circumference is removed, othermethods should be considered since maximumsalvageability of the thread plug is always desired.One possibility is the use of hardened lock nuts withtheir faces ground square with the axis of the thread.

4,2.2.4.2 When the step or’ flat method is applied,it is cut on the threaded cylinder at 90° with theaxis and to a depth sufficient to provide for com-parison of the part with the gage hy either feelingwith a fingernail or by the use of a straightedge.The step shall he placed circumferentially so that atleast one half of the full form of the tread remainsnt thecentirof the flat, Unless the depth require-ment is an exact multiple of the pitch, the threadstart at the” full form will not fall on the centerlineof the step. If both a max and a min step aredesired, they chould be placed 90” apart.

4.2.2.4.3 When a Go thread plug gage is designedto include a depth requirement, the gage chalk heclassified as Special. If the gage is a Unified orAmerican N8tinna! Standard thread, the design datafor the major diameter, pitch dia,meter, androot

clearance, etc., shall to taken from the appropriateMil-Std.

4.2.2.5 Handks. All thread plug designs are tobe single end and the handle shotild be in accord-ance with American Gage Design CommercialStandard CS8. Aluminum handles shall he”usedforallthreadp lugs. AGD standard thread blanksshould be specified wherever possible.

4.2.2.5.1 The Not Go, tri-lock blank shall bespecified for Go thread plugs ii sizes above 1.510and with pitches finer than 16 threads per inchunless a special requirement necessitates the use ofthelonger Go blank.

4.2.2.5.2 Tbe Not Go taper lock blank chall bespecified for Go thread plug gages which have depthsteps wheiiever the blank has sufficient length toallow for grindhg a flat on the back face of the plug.

4.2.2.6 Segment Type Thread Plugs. The,opera-~on of screwing solid thread plug gages, in and outof the part is a time-consuming and monotonousoperation. Several types of retractable segmentthread plugs have been developed to eliminate thisoperation andreduce inspection time. Thesegnrenttype gage isconstmcted co that the expanded posi-tion of the spring loaded segments is indicated by adial indicator.

4.2.2.6.1 Tbe expanding type gage is not satis-factory for inspecting both the maximum metal (go)and minimum metal (not go) Iimits simultaneously.This is due to the fact that standard gaging practicerequires asmaller trwncationon the major diameterof the Go member than on the Not Go member toinsure thorough inspection. Therefore, segmenttype gages must be supplied in pairs for a cOmple~inspection, i.e., one gage for each limit. The gagetruncations and root clearance should follow standardthread plug gage practice.

4.2.2.6:2 A solid type thread ring gage is recom-mended for setting segment type plug gages. Athread check plug is required for the manufacturingand acceptance inspection of the setting ring gage.A ceparate drawing shall be prepared for each unit.

4.2.2.6.3 The initial cpst of a complete set of

=Went tYPe pkg gages for an internal thread isrelatively high and, therefore, this type of gagingshould be employed only on standardized highproduction types of materiel so that the cost can bereadily amc:tized by subsequent savings in inspec-tion.

4.2.2.7 Roll Thread Plug, Bar Type. This type

of gage utilizes two thread rolls of small diameterwhich aie mounted on the spring loaded telescopingcenter bar which serves to expand and set tbe rollsfirmly inthepart beirig inspected. A gaging buttonis mounted on each member of the telescoping centerbar. Acceptability of the part is determined bytrying either a Go or Not Go feeler plug or both be-tween the buttons depending on the design of therolls. The same general principles as outlined in4.2,2.6.1 apply torollthread plug gages.

4.2.2.7.1 The bar type roll thread gage may bespecified for gaging threaded holes 7“ in diameter orlarger. Gaging rolls can bemadeto check 60” form,Whitwm-th, Acme, Buttress and other specia! forms.The thread’form on the thread roll is ground as acylinder rather than onthetnre helix and, therefore,

cannot be successfully applied to threads having alarge helix angle (7” or greater) or to multiplethreads.

4.2.2.7.2 This type of gage will afford sufficientaccuracy for most large dkmeter applications if thegage isuced carefully. Since the cost of the gage isrela~vely low, it is especially applicable to lowprodfi~tion items. Thegage.s can besalvaged easilysince the rolls are replaceable.

66 AGO10117A


4.2.3 GAGES FOR EXTERNAL THREADS.Thread ring gages are the most conventional meansof checking external threads such as those found ona screw.

4.2.3.1 Go Thread liin~. A Go thread ring isdesigned to check the maximum pitch diameter, the

clearance at the minor diameter, the ]ead and the

flank angle simultaneously. When an externalthread on a part entersa Go ring gage completely,assembly with the mating internal thread is assured

with only the major diameter of the part requiringfurther inspection.

4.2.3.1.1 Chip Grooves. Chip grooves are notapplied on thread ring gages, The design of theAmerican Gage Design Standard adjustable typeblank includes three (3) slots which SeI.Veas chipgrooves.

4.2.3.2 Not Go Thread Ring. A Not Go threadring is designed to check only one element, the pitchdiameter, to insure that it is not below tbe minimum

limit. Forthis reason, thethread form o” the ringgage is truncated at the minor diameter and clearedat the root so that the gage only makes contact uponthe central portion of the part thread flanks, Theclearance at the root may be omitted on thread ringgages for 28 pitch and finer since it is impractimd toprovide clearance on fine pitches.

4.2.3.3 Thread Ring Gages, Types. Thread ringgages can be successfully prnduced in either the solidor American Gage Design Standard adjustable types.The term “adjustable” must be considered with

caution. The gage may be adjustcdup to .6005.However, this adjustment is used only insofar as it isnecessary to obtain a proper feel on the setting plug.

4.2.3.3.1 G%@ Blanks. American Gage DesignStandard thread ring blanks should be specifiedwherever possible.

4.2.3.4 Tfwend Setting Pl~Gages. Thread cettingplug gages are required for the manufacture, accept-ance inspection, and subsequent surveillance of solidand adjustable type thread rings, roll thread snap,

segment type snaps, and other indicating type gages.

4.2.3.4.1 All thread setting plugs including thoseused fnr thread ring elements on fixture gages shallkmdesigned having both a full form and a tmncatedmajor d]ameter, except when a setting plug is re-quired fora blind thread ring element on a fixturegage, in which cacea full form major diameter eet-ting plug shall be designed.

AGO 10117A 67

MIL-HDBK-204

4.2.3,5 Thread Ring Minor Diam.ctcr ‘AcceptancePlugs, Thread ringgageshaving r,ominaldiametersunder .375 generally cannot be measured in alllaboratories due to limitations of the measuringequipment. Therefore, itisnecessary toinspect theminor diameter after the thread ring has beenproperly set tot.hethread setting plug. Two plainplug gages are required for adequate inspection.

4.2.3.5.1 A separate drawing shall be preparedfor each gaging element provided the desired sizeis not listed in MIHTDS 116 and 117. The gageshall beknown asan Acceptance Check, Note thatthe gagemaker’s tolerance is in a minus directionon the Go element and in a plus direction on theNot Goelement, tbereversc of conventional gagingpractice.

4.2.3,6 Major Diametzr Adjustable Snaps. Themost conventional method of inspecting tbe limitsof the major diameter of external threads is by theuscofadjustable snap gages. The Go portion insuresagainst oversize major diameters and the Not Goportion insures that there is sufficient depth ofthread.

4.2.3.6.1 MIIATD-118 lists the various stocknumbers forumet plain adjustable snap gages. Itis preferred that the square button type (ModelsMC or C) be used for gaging the major diameter.The method shown in the Standard for specifyingthe proper stock number, setting size, etc., shall befollowed.

4.2.3.7 Length Requirement. Occasionally, an ex-ternal thread specification will include a requirementforminimum length of full formthread. Thelengthshall be considered to be to the center line of a fullform thread space on the component external thread,unless other-wise specified.

4.2.3,7.1 The rear face of the Go thread ringblank may be ground square with the axis if thelength inspected closely approximates the length ofeither athickor thin blank. Ifthe length specifiedinconsiderably Iessthsn the thicknewof a standardblank, thegage may becounterbored from one sideand the oppnsite face ground square with the threadaxis to provide a surface for comparison of the partto the gage by feel with the fingernail or by uce of astraight edge. The leadlng thread on the threadring must be convoluted (removed) to a’full threadform.


MIL-HDBK-204; , . ...... .... ....,.

,4.2.3.7.2 Care must be exercised to ipsurq.$hatme ciosi+cetiofi, Of the finishd’ ‘ring, gage i:, ?o~ coiiiefilar that dktotiioi bill occur yhen hardening.

4.2.3.7.3 When a thread ring gage is designed toihclude”a length requirement, the gage shall beclassified as Special. If the gage is a Unified orAmerican National Standard thread, the designdata f?rthemajbr diameter, pitch diameter, minordiametim and root, cliaranoe, etc., cball be takenfrom theaPPropriate’ Mil-Std.

‘4.2.3.8 Thread Ring Gage, Segment Tfipe. Theoperation of screwing thread ring gages on and off apart is time-consuming and monotonous.’ Severaltypes of segment thread rings haie been developed

,.to eliminate this operation and reduce inspection/iine. The segment type ring gage is constructedso that contact is obtained on approximately 75%of the thread circumference and approximates threadring gaging actio,l. The segments are mounted on

pivots to allow fast, one pass gaging of the full lengthof thread;

4.2.3.8.1 The segment type gage is more expen-

sive than standard ring gages but the cost can usuallybe amortized from the savings in inspection time.

4.2.3.9 Roll Threag! Snap Gapes. This type ofgage utilizes two thread rolls of crnall diameterrnourited on opposite sides of a,’’C’’frame. Whereboth the Go and Not Go “limits are to be inspected,a set ,of rolls is mounted for each function, Thethread form on the rolls must be truncated andeffectively cleared in accordance with normal ringgage practice.

4.2.3.9.1 Gaging rolla can be’rnade to clieck notonly the 60” Form; but Whitwofih, Acme, Buttress,anduthers pecialfcmhm Thetiiread fiirni is groundisacylinder rather th’afion titruelielix and, there-fore, cannot be successfully applied to th;eads’h~~inga large helix angle (7° or” greater) or to multiplethreads. , .’

4.2.3.9.2 This type of gage’ will afford sufficientaccuracy for a kirge percentage of applications butmust. be specified with caution. ,,

4.2.3.9.3 When roll thread snap gages are specifiedfor high production items, it is good practice to alsosupply a thread’ring gage fdr”use in spot checking.

4.2.4 TOLERANCES AND .i;LOWANCES.

4.2.4 .lTolerancei..for both .Unified and Americanh~at~onil forms are in accordance with H28, Screw,.. :Thread Standards .f6r Federal S,erivices.

4.2.4.2 Standard tolerances for thread plug andring gages are of three classes:

(1;

(2)

(3)

,,“W” tolerances which represent the highestcommercial grade of accuracy and are

applicable to the lead and flank angle ofall setting plugs regardless of class. “W”tolerances may also be applied to pitchdiameters iftheclass of fitwarrantsit.“X” tolerances are larger than ‘<W” toler.

antes and are an economical compromiseamong such factors as gage cost, amount ofpart tolerance consumed by gage tolerance,etc. “X’ tolerances are generally appli-cable to all inspection gages and to pitchdiameters of setting plugs,

“Y” tolerances include a wear allowanceand are applicable on thread plug and ringgages where a little extra gage life is de-sired.

4.2.4.3 Tolerances on lead are specified as anallowable variation between any two threads nntfarther apart than the length of a standard gageomitting one full turn at each end. In the case ofsetting plugs, the length shall be that of the threadin the mating thread ring, On truncated settingplugs, any lead error shall be the same on the fullform portion as on the truncated portion and shallbe uniform within .0001 over any portion equivalentin length to that of the mating thread ring.

4.2.4.4 Tolerances arespecified ontheflankaL]glerather than the included angle to insure that thethread form is perpendicular to the ixii of the thread.

4.2.4.5 Tolerances onlead, flank angle, and pitch

diameter are noncumulative; thatis, the tnleranceon any one element may not be exceeded eventhough the errors in the other two elements are,smaller than the respective tolerances.

4.2.4.6 Thread gages for UNC, UNF, UNEF,

8UN, 12UN, and 16UN threads are classified MMilitary Standards. In the event that the part.

specifications for an NS thread are such that aMil-Std gage element can be used, the applicableMilPStd stock number shall be referenced on thesupply list and an appropriate note added as auaid to inspection personnel, (Mil–Std XXXXXXXis applicable to Go P.D, for XXX–XXNS-XThread, j

4.2.5 IDENTIFICATION-DA TA

4.2.5.1 The identification data block for threadgages shall include complete thread designation as

68 AGo 10117A


to nominal size, threads per. inch, thread series,class of fit, and product pitch d]ameter ~ize.’ In

specifying the nominal thread size, pitch diameter,etc., the decimal form shall be used.

When a thread gage is designed to inspect anadditional dimensional feature cuch as depth, out-of.squareness, etc., this information. shall be includedin the identification data block together with the

complete thread designation as outlined above.

4.2.5.2 The data on Not Go gages for UNS andNS threads challalsoinclude the length of engage-ment (LE) to which gage applies; for example:

lJIIGO-32NS-2NOT GO PD 1.4851LE 1.5

This is necessary as a result of the varying tolerances

applied tO the dfferent ranges of length of engage-ment. Skce the tolerances for Unified threadsare based on a particular number of pitches and

appfied tO all len@hs of engagement up to IMdiam@ers, it will not be necesmry t,o indic~~ theparticular range in the thread designation.

4.2,5.3 When the thread data given on the partdrawing is not in accordance with the tables in

H28, the following will apply:

(1)

(2)

When a product has a non-standard (notin accordance with H28) major or minordiameter, the Go and Not Go pitch dia-meter thread gages will be designed ac-cording to standard thread data providingthe major or minor dhmeters clear thepart.

When the product thread data dictatesthat a non-standard major or minor diam-eta’ on tbe gage is necessary to provideClearance, or the pitch diameter of theprodwt is a non-standard size, then thegage fox the element and limit that is notstandard should be marked NON STD inplace of the usual class of thread. As anexample, the correct upper limit of thepitch diameter of a 1.50-32 NS-2B productthread is 1.4849, For reasons of design, apitch diameter tolerance of .0083 is us, dmaking the upper limit 1,4S8, The ISotGo plug gage for this element and ‘limitshould bc marked: /

1.5W32NS-Nob, STD ,.

N(}T GO P]> 1,4s8

M1l-HDLiK-204

4.2.6 GAGES FOR MULTIPLE THREADS.A multiple thread is defined as one that has i leadwhich is an integral multiple of the pitch.

4.2.6.1 Undesigning gages formultiple threads, thedesigner is cautioned to ‘make a thorough investiga-tion of all features of the thread befmc proceeding

with thedecign. Ingenerall thedecign data forthemajor, pitch, and minor dtameters, root clearance,chip grooves, and tolerance on half angle is identicalwith single pitch threads. Inaddition, thepitch andIeadof thethread must aleobespecifjed. Multiplelead threads will be classified Special, since it ishighly desirable to maintain a reference to theapplicable component parts.

4.2.6.2 Thethread starts at bothendsof thegageshould have the thread removed to a full form.Note that this will not require the removal of a fullturn as is the caec for a single pitch thread gage.A thread having a lead which is twice the pitch willhave the thread convoluted for a half turn and willrequire two chip grooves (go thread plug) incterdof one.

4.2.6.3 In designing not gothread gage elementsfor multiple threads, it is desirable to desigp gageswhich have only a single thread start but with theproper lead, in order to facilitate the inspection ofeach thread start individually. The length ofthread should be cuch as to provide lx turns ifpractical as to an aid in measwement. Thismethod of design facilitates an economical andaccurate inspection.

4.2.6.4 Thedata block slmllcontain the completethread designation as specified in paragraph 4.2.5and sballalsoinclurle the Ieadsnd pitch.

4.2.6.5 Thelabel’’MULTIPLE THREAD> >~allbe placedin a conspicuous position on the drawingin ~“ high letters.

4.3 OTHER THREAD FORMS

4.3. I PIPE THREADS, Ameriaan Standardpipe threads are 60° threads designed on the sameorder as the Unified and American ,National Threadspreviously described. Some are different only inthe truncation while others differ in both the trunca-tion and the fact that they are cut upon & conerather than a cylinder.

4.3.1.1 TaperPipe Threads. Taper pipe threadsare 60” form threads cut on a cylinder with a taperOf 1 in 16, or .75 inch per foot, measured ~il tbe

AGO1O117A69


MIL-HD6K-204.

diameter and along the uxis. There are two basicpipe thread series differing primarily in the.degreeof truncation of the thread.

4.3.1.1:1 IVPT Pipe Threads. The AmericanStandard taper pipe thread, designatedas NPT, isdesigned for low pressure application and requiresthe weof asealing cornpoundto give a leak-proof

joint. In consequence, “the gaging approach israther simple. A taper thread plug gage for theinternal threads and a taper thread ring gage fortheexterna[ tfneads are sufficient. A taper threadplug andplain taper plug am also required for themanufacture and acceptance inspection of the taperthreading. Steps are cut in the thread plug andririg gages to indkate the limits that the gages m~yenter into or uptin the part threads.

4.3.1.1.2 I’(PTF Pipe Threads. NPTf? or DrySeal taper pipe threads are designed for uae withouta amder. The threads are so designed that whenmated hand tight thecrests and roots of the threadsare just touching. When wrench-tight, the crestsand roots are crushed together giving a metal tometal seal. To provide this series of actions, closecontrol of the taper of thethreads and of thetrunca-tion of thecrests is imperative.

4.3.1 .1.2.1 Gaginp Internal ‘f’breads. Internalthreads are gaged utilizing two taper thread plugsand one plain taper step pfug, The two taperthread plug’s lengths and diameters are so relatedthat one checks primarily the lower end of the taperon the component and the other checks the upperend, thus givinga more accurate check of the taperthan a single plug. Steps are provided on the plugeto aid in evaluating the component condition.These steps me provided at the basic cond]tion anda turn and a half either side of basic. The twogagesmust enter the part to or near the correspond.ing steps in order to have an acceptable part, Theplain taper step plug also has steps which corres.pond to those on the taper thread plugs so that allthree gages must enter previously determinedamounts for an acceptable part. The approach togaging external taper pipe threads is the same asthat outlined for internal threads except that twotaper thread rings and a plain taper step ting areemployed. Further, it is necessary to provide aplain taper plug and taper thread plug for eachthresd ring ,md a plain taper plug for the plaintaper step ring for purpnaes of manufacture, accep-tance and surveillance.

4.3.2 Acme Threads. The design data for regularand Stub Acme thread gages is available in Hand-book H28, Screw Thread Standards for Federal

Services. Condensation of the design data forStub Acme gages has not been accomplished;therefore, H28 shall be used. Design data for the

General Purpose thread and the Centralizing threadhas ,been condensed and is prssented here. Thethree claaaes of general purpose threads have clear-ances on all dkmeters for free movement and maybe used in assemblies where the screw is containedin a bearing or bearinge and the nut is rigidly fixed.The five classes of centralizing threads have a limitedclearance at major dtameter of screw and nut sothat bearing at major diameter maintains approxi-mate alignment of the thread axis. For any com-bination of these five classes of screws and nuts, somebacklash or end play will be obtained. If this is objec-tionable, one of three practices has been usedasfollows:

(1) The nut is split parallel with the axis andlapped to fit tbe screw.

(2) The nut is tappsd first and the screw ismachined to fit the nut.

(3) The nut is split perpendicularly to the axisand the two parts are adjusted to bear onthe opposite flanks of the screw.

The gage design data fnr these eight classificationsof Acme threads follow. Unless otherwise noted,all design values will be extracted from table X.

4.4 INVOLUTE SPLINES AND SERRATIONS.Involute splines and serrations are multiple keys inthe general form of internal and external involutegear teeth, m used to prevent relative rotation ofcylindrically fitted machine parts. The form ofthe tooth is made an involute primarily because it isself-locating in finding a full side bearing under load,and can be manufactured by the same machineused to generate involute gears. For purpnses ofgaging, the terms $pline and Scrration can be usedinterchangeably. Therefore, wherever the termspline is used, it also pertains to serrations.

4.4.1 INVOLUTE SPLINE GAGING. Thetwo main objectives in the inspection of involutesplines and serrations are: (a) the assurance of inter-changeable asaembly “by controi of effective fit,achieved by use of composite gages; and (b) thedimensional control of parts, obtained by checkingthe space width or tooth thickness, major and minordiameter.

70 AGO 10117A


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AGO 10117A 71


~lL_HDBK_2@,,

3:. ,,

. Amount pitch

., . dia of ‘IgO’vNcnuinal Major Length of ring shall be

Diameter of Screw “SO” ring gage less than max(max) pitch dia of

screw1

Abwe To and Incl 1 2

Inches Inchee Inch

o“ 1 2 diameters1 1 118 2 inches 0.00121 118 1 lif+ 2 inches .00121 114 1 318 2 inches~ 3~8 ~~

.00151 112 2 inches .0015

f: ,Y21“ 31’4 2 inches .0015

1 3?~t. 2 2 inches .00192 2 Uh 2 112 inches .0019

21/4. 2 1/2 2 1/2 inch.% .0019 ‘-

2 1/2 ~~ 2 316 2 1/2 inches .0019y ,3 -’. 3 inches .0019

4 3 inches4

.00275, 3 inches .0039

m-l% : - .The above compensation is based on a length’of engagement of twodtameters and on a.l,ead error in the product not “exceeding the followingvalues (in inches)

0.0003 i.:) length of 1/2 inch or less.’OOOb in length over 1/2 to 1 1/2 inches.0005 in lengtl(over.1 1/2 to 3 inches.0007 in length over 3 to’6 inches

..0010 k length over 6 to 10 inches.. :’,,

The leo~ths noted,,in CO1. 1. are a contprorhise fnr reasons of economy a-Ilrnitaticms of matwfaccure. To insure positive interchangeability gage! er,gths should approximate the product length of en,la:ysnumt.

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MIL-HDBK-204

PITCH DIAMWR ALLO!44NOESON EXTERNAL

NOMINALS12E SANGE THMA4D3, GERR4L ?ORP03E ANTJCENTRALIZING.

SIJ.W?S 2.G,2.C, cLA3”sEs”3G, -x ‘- CLA”35??S,$(2, (@J

& 5C ,008+ & a .006 + .004 q :— .—Q .... . . ..

Above To and Incl. 1 2 3

0 3116 .0024 .0018 I3f 16

.00125116 .0040 .0030 .0020

5f 16 7116 .0049 .00377/16

.00249116 .0057 .0042

9/16..0028

11/16 .0063 .0047 .0032

11/16 13/16 .0069 .0052 .003513/16 15116 .0075 .0056 .003715/ 16 1 1/16 .0080 .0060 .00401 1/16 1 3/16 ,0085 .0064 .00421 3/16 1 5116 .0089 .0067 .0045

1 5/16 1 7/16 .00941 7/16

.0070 .00471 9/16’ .0098 .0073

1 9/16.0049

1 718 .0105 .0079 .00521 718 2 118 .0113 .0085 .00572 1/8 2 3/8 .0120 .0090 .00602 3/8 2 5f8 .0126 .0095 .0063

2 515 2 7f8 .0133 .0099 .00662 718 3 1/4 .0140 .0105, .00703 114 3 3/4 .0150 .0112 .00753 314 4 114 .0160 .0120 .00804 1{4 4314 .01?0 .0127 .00854 3/4 5 1/2 .0181 .0136 .0091

lAn increase of 10 .Percent in the al lownce i.g recmnded .f or each inch,or f ract ion thereof, that the length of engagement exceeds 2 diameters. Thevalues in columns 1, 2 and 3 are to be used for any size within the nominalaize range. These values are calculated f rout the mean of the nominal sizerange.

TAB.~ XII. Pitch diameter ailowmc.s on eztemal threads, general purpose and cenirali.ing.

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‘IGO” Thread Plug GagesA, CENTRALIZING ACME THREAOS

1. Major Diameter = MinimumMajor Dia. of NutTolerance—Figure in col, 15, 16, 17, 18, 19, 20, or 21 (apply ph8)

2. Width Crest Flat = Figure in Ccd 6 (both comerz at the crest shall be cbarnfered equally at an angle of 45” withaxis of thread)

Tolera”c+Figure in COI7 (apply minus)NOTE: Crest Flat ‘(Mwt be Central”

3. Pb.ch l>iameter = Minimum Pitch Dia. NutTolerance—Figure in Col 11 or 12 (apply plus)

4. Miwm Diameter ~ Minimum Minor Dia. N@ (–) minus .010 (MUST CLEAR)5. Length = Appro~imately the length of engagement, but not excced,ng twice the “mnimd Major

u“lesa otherwise specified.6. Tolerance on Half Angle = F@. i“’Cd 13 (apply plus & minus)7. Variation in Lezd = Figure i“ CM 22, 23, 24 or 25

B. GENERAL PURPOSE ACME THREADS1. Major Hiamet.m = Minimum Major Nut (–) mims figme i“ Cd 14

Tolemmce = Figure in CM 10 (apply PIu8)2. Pitch Diameter = Mi”irnu,m Pitch Dia. Nut

Tcdemmce = Figure i“ Cd 11 or 12 (apply pl.$)3. Mimr Diameter = Minimum Mimx Oin. Nut (–) minus ,Olff (MUST CLEAR)4. Length = ApprOxima~ly tbc length Of engagement but not exceed,ng twice tt,. .Ominal Wor l)i~.

mdem’otherwise apecifiod5, Tolerance.. Half Angle = Fig”rei” Cd 1:3(apply PIUS &,minus)6. Variation in Le%d = F@m i“”Col 22, 23,24, 25

“Not Go” Majm Dia. ‘ThdPlug Gage, for CentralizingAorta ?’hwxl1. Major Diameter = Maximum Major Oia. Nut

Tolerrmce-Figure i“Col 15, 16, 17, 1S, 19, 20, or 21 (apply rni”w)2. Pitch Hi.meter = Maxinium Pitch Dia. of the Clam 4C screw (for Classes 2., 3. and 4.) or maximum pitch

diameter of the CIW 6Cscrew (for Classes 5. nnd 6c) -Tcderame-Twice the figure in cd 12 (apply minus)

3. W,dth Crest Flat = Figwe in Col 5 (both comers M the meat nball he cbwnfered eq”a.lly at :m mglc of .150withaxis of thread)

ToIertmce-Figwe i“ Cd 7 (apply rnimn)NOTE: Crest Flat ‘<Mint be Cmtrsd”

4. Mimm Diameter = Nfi”imwn Minor Oia. N“t (–) mims .01 (MUST CLEAR)5. Length , = 3P rni” Ro””d off to nw.rest ,~”*

4P ma,6. Tolerance on Half Angle = Figure i. Col 13 (apply plm tmd minus)7. Variation in Lead = Flgmc,in ,Col 22, 23, 24, 25

‘<NotGo” Pitch Dimneler Y’hdPlug Gagesfcw Gerwol Pwpw &’ (,’enlra[iz{ngAcme Thds1, Major Diametm = Maximum Me.jor Dia. Screw—Mi”w figure i“ Cd 2

Tolere.me—Figwe i“ Cal 10 (apply minus)2. Pitch Diameter = Maximum Pitch Dia. Nut

Tolerwme-Figme i“ Cd 11 (apply mi””s)3. Mimm Diameter = Mi”immn Mimm Dia. N“t (-) rnims :010 (MUST CLEAR)4. Root ClemP.me (Optiomd) = Figure in Co] 4 Max.5. Length = 3P Mi” Ro.”d off to nee.re~t ,~-*

4P Mm6. Tolerance on Half Angle = Figure i“ Cd 13 ‘(apply plus & mi”m)7. Variatim i“ Lad = Figure in Cd 22, 23, 24, 25

“0.” Thread Ring or Snap GageCentralizingAcne Thma&1. Major Hiameter = Maximwn Major Dia. screw (+) plus .010 must clear2, Pitch Diameter = Fit to setting plug3. Minor Dbmeter = Minimum Minor Diameter of the Nut ( -) minus: Clizs.ws 2C & 5. = Col 1, Table XII

Classes 3C & 6. = Cd 2, Table XIIClam 4C = Col 3, Table XII

Toler8nce—Figwe i“ (%110 (apply mimm)

.Wh.n a multiplethreadininYo1.ed,themotg. threadD1.gshallh .f mucha la@h as t. pmvideat lees 1 f.11turnof thread.

74 AGO 101I7A


4. Length5. Tolerance on Half Angle6. Variationin Lead

.1. Major f)iamete_FuO

Trunc

2. Pitch Diameter

3. Minor Diameter4. Lmgth5. Tolerancem Hdf Angle6. Variation in Lead

1. Major DiameterZ. Pitch Diameter3. Minor Diameter

4. Length

5. Tolerance on Half Angle6. Variation in Lead

1. Major I)iameter-Full

2. Pitch Diamete,

3. Minor Diameter4, Length5. Tolerance on Hzlf Angle6. Variation in Lead

1. Major Diameter2; Pitch Diamefer3. Minor Dsametm

4. Length

MIL-HDBK-204

= Approximately thelen@h ofengagement butnotexced,"g Co] l, Table X1= Figure i” Col13(applyplu8 &Minua)= Fig”rei” Co122,23 ,24,25

‘(Go” ThreadSettingPlugCenhIizing Acme Threads

= Maxirrmm ?vfajordimnet erwmewTolemme-Figmein CcJ 10(applyplu8)

= Maxim”ti major diametir screw (-)minus Fig”rein Co13,Tcdenmc~Figwein Col 10(applyrni”.a)

= If thele”gthofe ”gageme”te xcw&thele”gth of the ring gage, thepitch diameter shallbeIW them Mazimum pitch diametevof the mrew by the mnrm”t shown in Co! 2, Tabk X1.

Tc4ersmx-Figure i“ Cd 11 m 12 (apply mi”w)= ShaOdee.r Minimwn minor dia. ofgothread ring or8nap= Skllbeapproximatily twiwthe length o(thego tti~etd rimgo~t\,!ead anap ‘= Fig”rein Col13(applypI~ &miD@= Figwwi”Co122,23,24,25

“Go” ThnndRingorS?apGa@GeneralPurpwe Acme Threads

= Maxim”m Major Dia, ~crew(+)pl”s,OI (MUST CLEAR)= Fittosetti”gpl”*= Maximum Minor Ilia, %ww(+)plus figure in Col14Toler?”ce—Fig”r: incollO(applyminu)

,.

= Appmximatdy the length of engagement, but not exceeding the length spccificd in Cd 1,Table XI

= Figure ir. CoI13(applyplu~ &mims)= Figure i” Co122,23,24,25

“Go” ThreadSeUingPlugsGmmalPurpasc Acme Threud8

- Maximwn Major Dia. screwTolerance-Figure in (%1.10 (aPPIYPhIS)

= Mmim”m Major D,s. screw (-) fiWrein C~13.Tolersnee—FiWre in Co110(applymin”8)

= Maximum Pitzh Dis. scriwTolertmc-Figure i“ COI11 m 12 (apply rnizmn)

=, Clear mi”im”m mi”ordiametirof “go” thread ring or.snap= AppToximaWly twice the@gthof thegothread ringormap= Figure i” Cal13(applypbm &mi””s)= Figure i” COi 22,23,24,25

“NotGo” Thmod R&we,S%aPGeneralPurpose &Cen[,afizing Thread

= Maxim”m major dis. screw (+)pl”s,Ol (MUST CLEAR)= Fittosetti”gpl.g= Min.mi”or& s.of”ut( +)pl”86g”rei”Co12Tolermme—Figwwi”Cul 10(8pply plus)

= 3P Mi” Round off ta mareat 14”4P Max

5. Root Clearatice (optional) = F]gurein’ Co14 maximum5.. Tolerameo” HrJf Angle = RWrei”.ti112 (apply p!”8 &mims)7. Variation in Lead = Figwe i“ Co! 22, 23, 24, 25

‘<NotGo” ThreadSeUingPlugGenera lPurpose&f2nlralizingThmad

1. Major l>iameter = Maxinmm m.jordkscrewTolerance-Figure in COl 10 (apPIY,pbm),,

Trunc = Maxim”m major dia. screw (-)minus Figure i” Cal:3 “’Tolerrmce—Figure ifi’Col 10(applymims)

2. Pitch Diameter = Minimmn Pitch DimneterxcrewTolerance—figure in Glllor12(apply pl.s)

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MI&HDBK-204

3. Minor Diameter4, Length5. Tolerance’on Half Angle6. Variation in Lead’

1. Go Diameter

2. Not Go Diameter

1. Go Diameter

2. Not Go Diameter

1. Go Diameter

2. Not Go Diameter ‘

= Shall clear minimum minor dia. of the not go thd ring gage= Sh.s)l be approximatelytwicethe lengthcdthenot go thd ringor threadmap gage= Figurein Cd 13 (apply plus & minus)= Figure in Cd 22; 23,24,25

“f%” and “N& W Plain P@ Gw8Minor Dia. GeneralPurpo8e8 & CmtrafizinpNul

= Minimum Minor Dia. NutTolerance-Figure i“ C!QI15, 16, 17, 18,19,20, or 21 (apply plus)

= Maximum Minor Dia. NutTolermce-Figure in Cd 15,16, 17, 1S,19,20, or 21 (apply minus)

“GO”ad “Not Co” ,%L?P8

Afajir Dia. General PurpowAcmeSCTew= Me.xim”m Major ‘Ilis. screw

Tolerance-Figure i“ (%1 10 (apply minus)

= Minimum Major Dia. screwToleranc~Figure in (XI 10 (apply PIUS)

“Go” a“d “Not ,GdrSnapaMajor Dia. CentralizingAcme Screw

= Maximum Major Dia. screwTolerance-Figure in Cd 15, 16,,17, 18, 19, 20, or 21 (apply minm)

= Minimum Major Dia. screwTolerance-Figure in Co] 15, 16, 17, 18, 19, ZO,or 21 (apply plus)

4.4.2 DEFINITION OF TERMS. The follow-ing definitions are given for the more importantterms pertaining to involute spfines and 8plinegages. They are the same, wherever potiible, asthoss in the latest A.S.A. ‘B5. 15 Involute Splines,Serrations and Inspection.

4.4.2.1 Effective Spw Width. The effective ~pacewidth of an internal spline is equal to the circulartooth thickness ofi the pitch circle of an imaginaryperfect external spline which would fit the internalspline without looseness or interference. >

4.4.2.2 Effectwe Tooth Thickness. The effectivetooth thickness of an external spline is equal to thecircular space width on the pitch circle of ari ima-ginary perfect internal spline which would fit tlieexternal spline without looseness or interference.

4.4.2.3 Effective Clearance (Positive or negative)between two splined parts is equal to the effectivespace width of the internal spline minus the effectivetooth thickness of the mating external spfine,Positive effective clearance indicates rotary motion,while negative effective clearance indicates an inter-ference or press fit condition.

4.4.2.4 Ejfectiue Fits. The fit between two matingsplined membem depends on the effective spacewidth of the internal spline and the effective tooththickness of the external, spfine. lf these twoeffective dimensions are equal, a metal-to-metalfit at two or more spots could exist. If the effective

space width is greater than the effective toothWlckness, then there will be clearance betweenmating splines. If the effective space width issmaller than the effective tooth thickness, thiscondition could result in interference or a pre~ fitbetween mating splines.

4,4.2.5 Allowable Errors. The following allow-able errors are unavoidable errors produced bymachine and cutting tool inaccuracies during themachining operation. Dutortion from heat treat-nient may cause additional errors.

4.4.2.5.1. Total Index Error is the greatest differ-~nce in any two teeth (adjacent or otherwise)

tktwben the actual and the perfect tooth spacingon the same circle. Measurements are taken fromone point selected as a reference, to the corres~nd-ing points on tbe same circle on all other teeth, andwill he affected by involute error and outmf-round-netw

4.4.2.5.2 Profile Error. Profile error is the devia-tion from the specified tooth profile. It is positivein the direction of maximum material and negativein the direction of minimum mnterial.

4.4.2.5.3 Paralle[i.sm Error. Parallelism error isthe deviation from a specified direction of the splineteeth on the pitch cylinder. It is usually measuredby traversing a dial indicator along the tooth face,normal to the pitch line, and parallel to the axis ofthe spline. This error should be specified on the

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product drawing, However, since it is usuallycontrolled within close tolerance, it should be disre-garded in determining the error allowance.

4.4.2.5.4 OUT-OF-ROUNDNESS is the deviationof the spline from a true circular configuration.

4.4.2.5.5 Effective Error. The effective error is

the accumulated effect of the spline errorc on thefit with the mating part.

4.4.2.6 Error Allowance. Error allowance is thepermkible effective error. Experience has shownthat the effect of individual spline errors oh the fit(effective error) islessthan their total, Therefore,instead of using the total of all, the errors, tbe errorallowance is60 percent of thesum. of twice theposi-tive profile error, the total index error and tbeparallelism error for the length of engagement.

4.4.2.6.1 Matftining Tolerance: Machining toler-ance is the permissible variation in actual spacewidth or actual tooth thickness.

4.4.2.6.2 Total Tolerance. Total Tolerance is themactining toleranm plus the error allowance,

4.4.2.7 Actual Space Width is the circular widthon the pitch circle of any single space. It is de-termined by measurement between pins, paddleplug or any other methcd which meaaures theactual distance acrose the space, directly or in.dbectly. Since there are ermrc present in theinternal spline, theactual space width must be madelarger thin the effective space width by the effect

of there errors. In short, the actual space widthis equal to the effective space width plus the errorallowance.

4.4.2.8 Actual Tuoth TMckness is the circularthickn~ on the pitch circle of ariy single tooth.It is determined by measuring over pins, calipers,snap gage, or any other methud which measures theactual distance across the tooth, directly or in-directly. Since errorc are present in the externalspline, the actual tooth thickness must be madelees than the effective tooth thickness by the amount

of the effect of these errors. In short, the actualtooth th]ckness is equal to the effective tooth thlck-neas minus the error allowance.

I 4.4.2.9 Nominal Clearance between two splined

I

membem is equal to the actual space width of theinternal sDline minus the actual tuoth thickness of

the external spline.’ It does not define” the fit be:twecn mating members, because of the effect oferrors. “

4.4.3, COMPLETE PRODUCT SPECIFICA-TIONS. In order to<design gages propdy, proper

.—

MIL-HDBK-204

product specifications must be recognized to de-tirrnineiftheyaread equateorcon-ect. Thespliriegage designer is cautioned to check whether thetablesin A.S.A B5.15 Involute $plines, Serratiom,and Inspection have been ucsd ta design the product,

4.4.3.1 Complete Prcduct Spccijcations for anInternal Splhe. The following items are considered

to ‘be the proper specifications for the InternalSpline:

Type of FitNumber of teethDiametral P]tchPressure AngleBase Ciicle Dia. RefTotal Index Errur Max (Any two teeth)Involute Profile Error T.I.R.Out-of-RoundnemMax Parallelism ErrorX.XXXX Max. Mesa. Between .XXXX Dia

Pins RefX. XXXX+.XXXX Minor Dai.X, XXXX+.XXXX Major Dai,’X.XXXX Ref. Pitch Dm.X.XXXX Form D]a.Max. Actual Circular Space WidthMin. Effective Circular Space WidthLength of Engagement

4.4.3.2 Complete Product Specifications for anEzterrwl ISpM.c. The following items are consideredto be the pruper specifications for the ExternalSpline:

Type of F]tNumber of TeethDkunetral PitchPressure AngleBase Circle Dia. RefTotaf Index Error Max (Any two teeth)Involute Profile Errur T.I,R,Out-uf-Roundness

.,

Max Pmalfeliim .ErrokX.XXXX—.XXXX Minor Dm.x.xxxX—.XXXX Major Dia. ‘

X.XXXX Ref. Pitch Dia.X.XXXX Form Dia.

Min. Actual Clrcufar Tooth Thickness ‘‘Max, Effective Circular Tooth TMckncscLength of Engagement

4.4.3.3 Standard Prodta$ts. If the dimeucions ofthe spline product were taken from standards, thespline product is eonsidertd to be standard andgiges can be designed as outlined in the text.

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4.4.3.4 NmStandurd Components. If the dimen-.

siom of the apline component were not taken,fromstandards, but are dimensioned in accordance, withthe concept of the standard, i.e.; effective ,size,.

dknensional size and allowable errors sh,own, theprocedure followed in deqigning the gages in thesame w for standard products. However, ~caremust. ’be taken,, in. making appropriate changeswherever necc.ssary.

4.4.4 INCOMPLETELY DIMENSIONEDPRODUCTS. If the product dmensions. were not

“ taken fromstandards andshowonly thepinmeasure-ments with no reference to effective size or actualsize, then the determination ,of gaging should bebased onthe following procedure. ,.

4.4.4.1 Incompletely Dimemioncd Internal Prcd-uct. In dealing with an internal spline havinggiven the maximum and minimum meamrementbetween pine, corresponding space widths should be

calculated. These sizes should be interpreted asthe maximum and minimum actual space widths.If no allowable errors are tabula~d on the productdrawing, error allowan~s should be tentatively

appfied and submitted to Pr@uct. Engineering forcoordination ,and ,,approval. Upon approval, theerror allowancesare subtrac@d from the. minimunractual space width. This b,ecomes the minimumeffective space width,,

,4.4.4.2 (ncompf@el~ +mm,tionzd Extir-rud,Pr@wt.., When the ex~rnal, product has shown amaximum and minimum measurement over pins,the corresponding tooth thickness should be cal-culated. The spread or tolerance “on thn tooth

thkknesc should be interpreted ”tiwthe’ rnact@ingtolerance for the external tooth: Jnterpret themaximum tooth thickness as determined fr6m themaximum effective tooth th]ckness. If no allow-able errors are tabulated on, the product ,driying,error allowances should be tentatively applied andsubmitted to Product Engineering for coordinationand approval. Upon approval,. subtract the errorallowance from the maximum effective tooth thick-ness to determine thepv+imum actual tooth thick-ness. Subtract the machlningt+lerance from tbemaximum actual tooth thicknm to establish theminimum aitual tooth thickness. The old measure-ment over pins is discarded and anew measurem-ent computed corresporidlngto the actual SiZ~S.

4~4.4~3E~ineer@gC@diktion, ,It is ass,um+that the, E@wering in,de~~ing the sp~ne hasprovided for, a certairi t~e”of fit; ’however,, tbe

prubab]lity exists that if no.error allowance wasgiven, the effective fit concept was not considered.Therefore, any change that is made to use theeffective .fit must be thoroughly coordhated withtbeProduct Engineer in order that reconsiderationof the spline lit can be made. This is particularlynecessary when changes alter the fit from the original

dimensional clearance fit to an effective interferencefit.

4.4.5 NOMENCLATURE. The nomenclaturefollowed is the same wherever pocsible as that in thelatest A.S.A. B5-15 Invol,ute Splines, Sermtions andInspection.

4.4.6 GAGES FOR INTERNAL INVOLUTESPLINES. To effectively gage an internal splineto assure proper fit andinterchangeabllity, a set ofthree gages is required, Go Composite Plug, GoPaddle Plug and Not Go Paddle Plug. PaddlePlugs are also known as Sector Plugs.

4.4.6.1 ,Go Composite Plug Gage is designed tocheck the minimum effective space width of theinternal spline. The gage has a full complementof teeth and checks m much profile as will be re-quired, by the mate. This gage is recommendedwithout exception.

4.4.6.2 Go Paddle Plug Gage isdesignedtocbecktherninimum actual space width. .Thegagehaa allof its teeth removed except two pairs located dia-metrically opposite each other, Themajor diameteris truncated, and tbe outside .form of the teeth re-

Iievedto minimize the effect of the allowable errors.This gage is recommended as a final inspection gageto be used only for the evaluation or rejection by GoComposite Plug Gage. It is seldom needed forbroacbed splines having a rather fixed tooth thick-ness, except to evaluate the rejections of tbe GoComposite Plugdue to fillet interference. Frequent-ly, it i? used asa machining gage or for control ofmachine settings.

4.4.6.3 Not Go Paddle Plug Gage is designed tocheck the maximum actual space width. This gageis recommended without exception.

4.4.7 GAGES FOR EXTERNAL INVOLUTESPLINES. To effectively gage anexternalsplineto asmire proper fit and interchangeability, a set offive gages is required: A Go Composite R]ng, aTapered Tooth, Maater Plug, aGo Snap, a Not GO

Snap and a Setting Master.4.4.7.1 Go Composite Ring Gage is designed to

check the maximum effective tooth thickness of theexternal spline. The gage has a full complement

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of teeth and checla”as much prnfile as will be rc.quired by the mate. , This gage is recommendedwithout exception. .,

4.4.7.2 Y’tipered’I’ooth Master, Th~gageis neverused to check the product. However, it is useful inthe manufacture of the Go Composite tilng Gage.This gage is of the plug type with a full complementof t,eeth. One side of each tooth is tapered slightlyto vary the tooth thickness. The opposite sides arenon-tapered providing a full length contact with thering gage. This provides a fit range and discardlimit on the gage. These muters are, for new ringgage acceptance and for determining when the ringis worn to the high limit of the part. The ring isfitted m a section on the maater which incorporatesa wear allowance on the ring. The ring gage ischecked periodically for wear with the taperedtooth master, and when the ring pnssei over thediscard limit on the large end of the master, it shouldbe replaced with a new ring. The majnr diameterof the master is not tapered. Tapered tooth mastersare recommended wherever a ririg gage is used, toassure the correct effective relation between thering gage and the plug gage used for the mating

part arid to acsure replacement of ring gagec of alike effective size,

4.4.7.3 Snap Gages. A snap gage is a gagearranged with npposing measuring surfaces separatedby a spacer or frame. It is designed to check theactual tooth thickness of an external spline. TheGo Snap Gage checks maximum actual tooth thick-ness. This gage is recommended as a final inspec-tion gage to be used for evaluation of rejection byGo Composite R]ng Gages, It is alsn used fre-quently as a machining gage or for control of mach]nesettings. The Nnt Go Snap Gage checks minimumactual tooth thickness. This gage is recommendedwithout exception,

4.4.7.3.1 Roller Type Snap Gages. The rollertyf-e snap gage is preferred wherever pnssible be-cause of the many advantages over the other typesof snap gages. The rollers are easily manufacturedand do not have to be held to close tolerance sincethey are set to a setting master and adjustedquickly by a sensitive eccentric. Slight changes intolerances on the product can be easily accommo-dated by adjusting tbe eccentric to a new settingmaster. The gaging surfaces of the rnllers arestraight sided and dn not require special machinesto manufacture. The wear life of the gage is greatly

increased due to the incresscd gaging surface on theflank of the roller, since wear is dbtributed over theroller. circumference. The disadvantage of thistype of gage, is ‘that it cannot be used wherever thespline is close to a shoulder of flange which wnuldprevent the roller from checking a sufficient lengthof spline.

4.4.7.3.2 Built-Up and Solid Type Snap Gages.The built UPor solid type snap gage is used whereverit is necessary to gage close tn a shoulder or Siinge,Disadvantages nf these types of gages are that.

they must be ground to extremely close limits duringmanufacture, and the wear life is greatly reducedbecause of its small gaging surfaces.

4.4.7.3.2.1 Built-Up Type Snap Gages are used ifthe major diameter of the component is less than1.500 inches. The built-up type, &s dktinguishedfrom the solid type, is. split in the center and heldtogether with screws and a key.

4.4.7.3.2.2 Solid Type Snap Gages are used onproducts whose major diameter is greater than1.500 inches. The measuring ~~surfaces of thesegages are integral with the frame.

4.4.7.4 Setting Maher for Go and Not’ Go SnapGnges. This gage is never used to check the cnm-ponent. Setting mnsters are used exclusively toset the Go and Not Go Rnller Snap Gages. Tbegage is nf the plug type having twn sets of teeth, onefor cctting the Go Snap and the other for settingthe h’ot Go Snap. For splines having ten teeth orless, setting mnsters become special problems and

must be dealt with as such, The gage is requiredfor setting the snap gages and detecting wear onthem. This gage is recommended, without excep-tion, whenever roller snap gages are used.

4.4.8 GAGE BLANKS.

4.4.8.1 Standard Gage Blanks. Standard gageblanks are to be used wherever possible. Standarddesigns for certain types of spline gage blanks arcavailable in the report of tbe American Gage DesignCommittee, U.S. Department of Commerce Com-mercial Standard CS-8–O 1, “Gage Blanks”, Insnme inctances, rather than design special gages,the standard design is modified to suit the particulargaging problem.

4.4.8.2 Special Gage Blanks. Special gage blanksare designed fnr gages for which no standard existedor where it is impassible to modify any existingdesign.

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4.4.9 MACHINING TOLERANCE AND AL-L41WABLE ERRORS FOR GAGES.

4.4.9.1 MmhiniWTofmanzc. Themacbiningtol-erince for @ges is the allowable variation in tooththicknms or space width permitted in the manu-facture of the gages. Since the Go ComposibRing Gage k fitted to the Tapered Tooth MasterPlug no tolerance is required on the measurement

between pins. The tolerance on measurement overpins should never be less than ,)002 except foraberrationshaving a dlametral pitch finer than 48/96,when closer tolerances must be used. The sign ofthe tolerance k always plus for the Go CompositePlugs plus and minus for the Go Paddle Plugs andminus for the Not Go Paddle Plugs. The TaperedTooth Master tolemnce ic plus on the kwge end andminus” on the small end. The Setting MasterTolerance ic plus and minus for the Go set of teethand plus for the N6t Go set of tci h.

4.4.9.2 Allowable Errors jor GWes. The allow.able errors encountered in manufacturing the com-ponent will also be encountered in manufacturingthe gage. Thecc errors must be spccificd on the gagedrawing. They arc kept cs small W. is feaaible tocontrol the, accuracy of the gage and yet not makethe cost of the gage pmlibltive,

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4.4.10 MEASURING PINS4.4.10.1 Detcrminiitg Proper Measuring Pins.

Since the measuring pins used for gages arc not thesame as the measuring pin used on the component,the gage designer must compute the pin diameter tohave contact occur as close to the pitch diameter aspossible. For standard aplines constants have beenestablished which when divided by the diametralpitch determine the pin diameter required for the@ge. If the spline is non-standard, the gagedt+igner must compute the pin diameter from variousformulas available so that contact will occur at adiameter near but outside the pitch diameter cmthe plug gage and near but inside the pitch diameteron the ring gage, The designer ie cautioned to usethe tooth thickness or space width correspondingto the diameter at which contact is to wxw indetermining the meaauring pin diameter for non-standard splints,

4.4.10.2 Selection of Measuring Pin, The selec-tion of the meaauring pin is made from the Table ofRecommended Standard Meacuring Pins. It isrecmuinended to always select the next larger pinh the computed diametir. In all cases, it is in-advisable to use flattened pins ‘W they are awkwardto usc rind wear mom readily.

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CHAPTER 5. OPTICS IN INSPECTION5.1 INTRODUCTION. Light is a moat versatile as the object is in front of it. See Figure 24.

tool in inspection. It maybe employed as auxiliary Mirrors are used in inspection to view inaccessibleillumination in visual inspection or run through the areas and in autocollimation.illu~nation ~ visual inspection or run through t~e 5.3 THE SIMPLE MAGNIFIER. Referring tooptical system of a,microscope or projector to, pro: “~F?gure 26, it is shown that the simple mangifier, PrO-vide’ a magnified image of the part. P@dlel (or,: ,,diices an image that is magnified and on the samecollimated) rays of light may be used to establish “side of the lens as the object; also, it is unreversed.reference lines and planes whM the patters frog ~~The singIe mangifier is subject tO bO~h ~hmma ticwaves interfering with each other may be,usid ai an ‘arid spherical aberration; i.e., except over a narrowultra precise me@ring tool through interferbrnetry .”” range the colors and shape of the image are dis-Finally the ultimate standard in our ‘system ‘Of~” ,,torted, However, within its Itilts, it is an excellent

dimensional measurement, the inch, is ‘defifi~” in’ production and inspection aid in that it can be usedterms of a preoise’ number of wavelength@’,of’.a ‘“~particular color type of light.

5.1.1 GENERAL NATURE OF LIGHT: Light’:’is a ,type of electromagnetic vibration and as such

appears to travel’ in’waves. Further, light is justone small segment of the entire electromagneticspectrum which rang= from powerline frequenciesthrough radio waves, infra red, then light followedbyx-rays and Gamma Rays. Vkible light is thatseries of wavelengths”from .0000157 to ,0000275inches. This series is arbitrarily dkided into sixbroad area.s-vilt?et, blue, green, yellow, orange,and red. Since the colors blend continuously, thiscan only be approxihmte. Figure 23 represents thevisible spectrum and the wavelength for each color,

5.1.2 GENERAL LAWS OF GEOMETRICAL

OPTICS. Light obeys certain fundamental lawswhich the equipment and processes outlined on tbe

fcd]owing pages employ toth6bestidvan@6. :

(a) Law of Rectilinear Pmpagatio\,,, Ijght “travels at a constant speed in a stifightIineina.medium ofconstantdefit,y.

(b) Law of Reflection. In paasingfrorna ,medkmof lesser density tooneof. greater,density, light is deviated toward the :normal. In passing from a medium ofgreater density to one of lemer density,light ia deviated away from the normal.

(c) Lawof Reflection. Theangle of reflectionis equal to the angle of incidence andlies on the opposite side of the normal;the angle of incidence being the angleformed between the rays strik]ng the

surface and the-normal,

5.2 MIRRORS. The simplest form of opticalsystem is the plane mirror which provides a reversedimage that appears h he M far” behind the rnlrrbr ‘

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to view visual defects more clearly, to aid in male when both are at infinity. Asmentioned previously,reading and to facilitate handling of small parts. A it is also equal to the dividend of tbe focal lengths.typical application is shown in figure 25, a bench If the ratio of image sizes is 30.1, the telescope ismagnifier. said to have a magnification of 30 which is written

5.4 THE MICROSCOPE. Whenever high as 30X or spoken of as 30 “power. (Occasionally, it

magnification is desired, the microscope is used, It may be referred to as 30 diameters. )

consists of two convm-ging lens (in practice, lens 5.5.1.2 Range. The range of a telescope is that

systems), an objective lens of very short focal length.. di~tallce w~thill which an Object ca[l be clearlYand an eyepiece of moderate focal length. The” “’~defined tirfocpsed. For example, the average align-

objective lens forms within the tube of the instki+ :..~(rn?rit type’ telescOPe can be sharply fOcused Over ament a somwhat magnified real image of the o“bject.” ~~.”r?ngi @ f~:m eighteen (18) inches tO infinity. AllThis image is magnified by the eyepiece which object less than eighteen (18) inches from the ohjec-

serves here as a simple magnifier. Thus, the final tive lens iarinoi be sharply focused.image, seen by tbc eye, is virtual, inverted’ and”. 5.5.1.3 Reso,hdiom ‘l’he ability of a telescope to

greatly magnified. By placing a graduated reticle distinguish bety.een two adjacent points is termedat the site of the real image, it is examined by the its resolving power. It is generally expressed ineye piece along with the real image, so a direct terms of the min”imum angle at which the two pointsmeasurement of distance, angle or form may be ‘ can be independently identified (or resolved). Themade. See figure 27. average telescope used for alignment purposes is

5.4.1 MICROSCOPES employed in inspectiori, rated ,,at,3% seconds. If’ two points on an objectare of two general types—work shop and toolmakers’ : are “being viewed which make a smaller angle tballwhich vary primarily in the degree of accuracy ., the angle of resolution, the image in the telescOPeavailable, with the toolmakers’ being more accurate. will only show one point.Tbe work shop microscope generally would have a 5.5.1:4 Field of View. This is defined as the openmagnification of 10X while the toolmakers’ would or’iisibk space the viewer can see through the tele-range from 10X to lOOX ill addition to having a cope .ylien it is stationary. It is the maximumtable which moves on coordinate slides with microm- angle subtended by any two objects which can beeter adjustment. Some toolmakers’ miscroscopcs vie}~ed simultaneously. It is generally expressed ascan be fitted with a projection head in, the layer “$0 many ‘“yards at 1000 yards”, but for opticalpowers so that the image may be” ~ier@ at “eye ‘ rneasurim::t, it’ is more likely tO be expressed i]~level on a screen. See figure 28. degrees between rays. An average alignment

5.5 TELESCOPES. A refracting telescope ‘pro- telescope would have a one degree angle betweenvides a magnified image of a distant objet(: , Re-. rays at thirty power. As the magnification of theferring to Figure. 29, two basic lenses arc used, an ‘‘ eyepiece, increases, the true field of view goes down,objective lens and an eyelens. A dktant, object ~’0” everything else being held equal.sends rays of light” through the objective ‘~M”. 5.5.2 TELESCOPE CONSTRUCTION. TheThese rays are focuse~ at “f” andthen ifter passing ““ “major parts of telescopes used in inspection are thethrough the eyepiece’’’!L” emerge in’ a parallel beam; .‘’ objective, the eyepiece, the focusing lens, and theenabling the eye “E” of an obsericr to see”an in- reticle (which together ‘form the lens system);verted image of “0”. The two.lenses are spaced a “., the mount, the eyepiece mounting and the focusingdistance equal to the sum of theiitfocal lengths and , ,mechanism,the magnification is equal to the focal .Iengthof the, “5.5.2.1” The Lens S@em. In the lens system, theobjective divided by the focal length of the eyelet~s. objective gathers and focuses the light from the

5.5.1 BASIC OPTICAL CHARACTERISTICS object.;” At the focal point is placed a glass discOF A TELESCOPE. There are f6ur optical with cross-lines etched into it. The eye lens viewscharacteristics of a telescope which should be defined this reticle and object image and provides an emhere. Iarged image for the observer. If then appears that

5.5.1.1 Power. The magnifying power of a tele- the cross-lines are superimposed upon the object.scope is the ratio of the apparent size of the object 5.5.2.2 The Mount. The muunt is a sturdy tubeas seen by the unaided eye to the apparent size of which holds the lens system and related mechanismsthe image seen in the eyepiece of the instrument in proper alignment.

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5.5.2.3 The Ev~”ece Mounting. It holds theeye lens in the proper relation to the rest of thesystem and provides an adjustment to be used tocompensate for variations in human eyesight, forclose focusing on the cros~lines of the reticle. Inan instrument with a reticle, either the objectivelens or both eyepiece and reticle must be adjustedto maintain focus on nearby objects.5.6 COLLIMATION

5.6.1 GENERA L, The basic collimator is anoptical instmment that is derived from the telescope.Light from a distant object enters the telescopeobjective lens in the form of parallel rays of light.Thexe rays are theri converged to a point on a reticleplaced attheprincipal focus of theobjectivelens. Areverce process is performed in the collimator dla-grammedin Figure 30. Alight source illuminates thereticle placed in the principal focus of the objectivelens. Light rays from the reticle are collimated(rendered parallel )bytheobjectiv elens. Theimageof the’ reticle appears at infinity. The collimator isused as an instrument in the inspection of optics andas a target in optical tooling, some phases of whichare discussed in par. 5,7.

5.6.2 ,AUTO-COLLIMATION. By combining

a telescope and a collimator into one instrument,auto-collimation is possible. Auto-collimation isachieved by sighting the instrument into a planemirror that reflects the rays coming out of theobjective lens back through the instmment. The

perpendicularity of the mirror with respect to theaxis of the auto-collimator may be ascertained byviewing together the reticle of the auto-collimatorand the reflected image superimposed thereon. Theeyepiece of the instrument is used to examineaccurately the degree of superposition.

5.6.3 CONSTRUCTION OF THE AUTO-

COLLIMATOR. With reference to F]gure 31, asimple auto-collimator is comprised of:

A. ReticleB. Objective LensC. Semi-ReflectorD. Eye lensE. Field LensF. Light Source

5.6.3.1 The reticle “A” is usually made of opticalglass with finely etched cross-lines. Sometimesadditional graduations may be included to indicatethe amount of deviation, as shown in Figure 32.

5.6.3.2 The Objective “B” renders the image ofthe reticle “A” into parallel rays of light. When a

reflecting surface is placid at any position perpen- ‘‘dicular to thess rays, they will be reflected backthrnugh the objective lens, and refocused on tbereticle surface.

5.6.3.3 Semi-Reflector “C” is a partially-coatedplane plate glacs mirrnr that reflects the light from .,the bulb of the light source into the lens system.

5.6.3.4 The Eye Lens “D” magnifies the reticlepattern and the real image fnrmed by the reflected “rays ssen on the Reticle “A”.

5.6.3.5 The illuminating Source “F” may varyfrom a 6 volt bulb built into the instrument to a highpowered separate external snurce concentrated onthe reflector “C”.

5.6.4 THEORY OF THE A UTO-COLLIMA -TOR. III any “reflected ray nf light, the. angle it

strikes tbe reflecting surface equals the angle it leavesthe surface. Therefnre, referring to F@e 31 .%gain,the angle formed between the prnjected rays and thereflected rays will be twice the angle.0 which thereflecting surface is tilted from the vertical. Theposition O{ the returned image on the reticle with .respect to the graduations themselves will be anamount equal to the tangent of 24 times the focallength (f) nf the objective lens. Therefore, bygraduating the reticle as in figure 32, the angle Oofthe reflecting surface can be determined.

5.6.4.1 Detsmnanatian of Accurnq. Since, asexplained above, the distance X is (f) (tan 26), if the ,desired accuracy is nne minute of arc, and assumingan objective “B” focal length of 10” the spacing of ..the graduations would be 10X tangent of 2 minutesor ,@58 inches. By using a longe~ focal length Of

objective lenses, the linear spacing nf the graduationsmay be increased thus permitting the measurementof smaller angles than 1 minute of arc. However,the length of the tube must got become unwieldy.

Increasing the pnwer of the eyepiece also increasesaccuracy and sensitivity but reduces the field of viewthus limiting the range of the graduated scale. Vi-bration of the instrument also tends to limit the

accuracy of observation in the smaller angles, Underthe best laborato~ conditions, accuracies Of .1second of arc are possible; under, average workingcondkions, one-half minutk is more’ practica}.

5.6.4.2 Adwmkiges of Z%ral~e~Ligf+ In using theautu-collimator, the.parallelism of the projected raysof light means that ‘the instrument can be umd atany distance from a reflecting surface withoutrefocusing or may be rotated about its axis, Theonly ill effect of long distances upon the function of ~

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the instmment would come from loss of clarity dueto entrance of stray light or the falling out of lightintensity as the square of the distance.

5.6.5 REFINEMENTS OF DESIGN. Thebasic auto-collimator, as discussed above, is themost versatile and easily adaptable version. IIow,-ever, there are variations of design which mayprovide greater accuracy at aeacrifice of mobility,

as rfiscussed below.

5.6.5.1 Micrometer Eyepiew; In figure 33(a) isan instrument similar to the basic instrument, exceptthat a micrometer eyepiece is used to view theimages. Iiw,tead ofreading thedisplacement directlyon the reticle, it is measured by the eyepiece. Theeyepiece has a fixed cross-line together with amovable cross-line actuated by a micrometer screw.In setting up, thetixed cros+lineof the eyepiece isset onthe cross-line in the reticle. Themicrometet

dial is then turned until the movable cross-linecoincides with tbe reflected image. The amount ofdkp\acementist hen read nn the micrometer dmmwhich can be so graduated as to read small incre-

mentsof angle directly. Thermrge of displacementis limited by the field of view of the micrometerwhich will he quite less than tbe regular eyepiece.

Micrometer eyepieces for standard auto-collimatorsare easily obtainable commercial items.

5.6.5.2 Microscope Eyepiece. To achieve stillgreater accuracies, a microscope may be used as aneyepiece. The field nf view is now so limited thatnearly all displacements would be outside of it.Therefore, the complete microscope is mounted on amicrometer actuated cross slide. A fine cross hair inthe microscope is lined up with the collimator reticlecrnss-line and then tbe micrometer drum is rotateduntil the cross hair is lined up with the reflectedimage. The difference in readings is the equivalentangle of deviation. Again the mic!ometex dmm maybe graduated in very small increments of angle.Further, the microscope allows more precise align-

ment of the eyepiece cross hair and reticle cross.line.See figure 33(b)

5.6.5.3. 0~-,4zis Pinhole Type. Figure 33(c)illustrates a refinement in the’ transmitted image.The light so”roe is mwv injected into the systemtbmugh a partially reflecting mirror but is off theaxis of the telescope. Light is concentrated on anextremely small hole (about .015 diameter) or fineslit located from the nbjective lens a dista.me equalto the focal length of that lens, The reticle is stillgraduated similar tn figure 32. For best optical

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performance, the displacement of slit and reticle “D”should be as small as practicable. Due w. thedistance “D”, the light rays must travel throughangle X. When the reflecting surface is perpen$cu-lar t? the bisector of angle X, the returning lightrays of the hole or slit will form an image in thecenter of the graduated reticle. This system has adistinct advantage in that the returning image is asimple, sharply defined, spot or line of fight. Thiseliminates reading the dkplncement of twn complexpatterns since the line or spot can easily be viewedagainkt the basic reticle pattmn.

5.6.5.4 Fiztrme Type CoUimatnr. Using the pm.vious principle together with a greatly increasedfocal length objective the fixture type collimator isevolved. To keep the instrument compact., ”threemirrors are used to fold the Imrg Iigi]t path into theframe casting, An adjustable table C8n be providedtn increass the versatility bf the instrument. It isvery useful for checking parallelism of glass surfaces(surface of optical flats) since the light is reflectedfrom the top and bottom surfaces simultaneously andthe displacement of the twn reflected images can benhtained d]rectly. By the provision of holdingdevices for the table, angularity of geometricalfigures may be easily checked. See Iigure 33(d).

5.6.6 APPLICATION 9F THE A U~O-COL-LIMX TOR. The following paragraphs illustratesome typed and basic applications nf the autn-col-Iimator to general measurement.

5.6.6.1 Angle Co-nparisnn. Figure 34 shows, theauto-collimator being used to compare an angle withthe corresponding angle of a master. Ninety degreesis illustrated but practically any angle could he sochecked. The axis of the auto-collimator is madeperpendicular to the surface of the master angle byadjusting its position untilthe reflectsd image 6f thereticle is lined up with the reticle itself, as seenthrough the eyepiece. The master angle is thenremoved and replaced by the angle being tested. Anerror in the angle nf the test piec. will thus displacethe reflected image. If the master and test piece canboth be contained within the fieid of view of theinstrument, it is well to leave the master in positionto serve as a constant check. For average work agood surface plate will do as a work hnhler, but fnr ahigh degree of accuracy, both pieces should be wrungto an optically flat surface.

5.6.6.2 Direct Angle Check An angle may betested by viewing the reflections from one of the

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faces and from an optical flat with which the otherface is in contact. Figure 35 shows the arrangement

for right angles. Two images are formed in theinstrument, one by light rays that etrike the flatfiret and the other .by rays that strike the face of thetest piece first. If the angle is precicely 90” the twosets of rays are parallel and the images coincide.With an angular error of 8, the two sets of rays forman angle equal to 48, the images showing a cor-responding separation. This method is very con-venient, since the instruments may be pointed down

at any convenient angle and the holding plateadjusted till both images are in the field of view.This method can be ueed to measure any simplesubmultiple of 180 degrees. For even portions of 90°(45° and 22,5°) the same freedom of elevation of thetelescope is precent as for the 90°; however, for otherangles such as 30”, 60°, 75°, the axis of the instrumentmust he parallel to the bisector of the test angle orthe beams will not return into tbe telescope,

5.6.6.3 IndirectAngle Checks. Checking un-polished surfaces presents a problem. One methodof doing thk’ is illustrated in F@re 36. A planemirror is laid on the inclined surfcce to be measuredand the bc.cc is cet on a polished flat. Two imageswill be produced as in the method of par. 5.6,6.2 butthe rays which strike the flat first are reflected fromthe mirror back to the flat, then to the mirror, andback to the instmment so that they are deflectedfour times tbe error in the test plane. The sameholds tme for the rays wh)ch strike the mirrorsurface first so that the two images in the instrumentwiU show a separation corre?mondlne to 8 times the.-ermr in angle of the test surface.

FIGURE 34. Ancle campximn for OOO.

AGO ,0117A 93

FIGURE 35.’ Direct anglecheckfar @

FIGUEE 3S Indirectanglecheck

5.6.6.4 Checking with a Sine-Bar. A sine bar maybe uced to extend the application o, the auto-collima-tor. In figure 37, the telescope is first adjustedperpendicular to the base plate then the upper mr-face of the sine bar is set to the complement of theangle to be verified. Deviations from this basicangle are recorded on the autc-collimator’s scale.Duplicate pieces can be checked rapidly hy thiemethod. Another method ie to set the sine bar to thebccic angle in question, place it on a surface plateand adjust the auto-collimator normal to the inclined

surface of the sine bar. It is moved ,aside and the

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FIGUUE 38. Opficallmer.

pieces to be checked are placed on the surface platefor comparison. This method also lends itself toproduction checking.

5.6.6.5 Tfu Opk’calLeuer. Themetbod in figure

38 can be used for either of two purposes. It can beused to check unpolished surfaces or it can be used togain magnification. In production inspection,’ acradle with a movable mirror to contact the surfacein question should be used.

5.6.6.6 Straigftitiss or Flatness Checks: Straight-ness of planes (or tlatness) may be checked by usinga vertical reflecting surface mounted on a movablesaddle, as in figure 39. The deviation from’ a true

surface in any plane may be read from the auto-collimator scale. Saddle plates may be designed foralmost any type of surface, such as Vee ways, surfaceplates, straight edges, etc.

5.6.6.7 Pmtdtelism. To check parallelism, tbeparts are ‘placed one upon the other and the reflectedimages from tbe surfaces to be compared are viewedin the auto-collimator. It is often more convenient

to have the instrument in a horizontal plane, espe-cially if the parts in question must be set vertically,so the set-up in figure 40 is employed, Here, the useof parallel light permits viewing two images travelingover distances which dhTer by twice the length of tbetop piece, yet they both are in focus.

5.6.6.8 .4zial Squareness. To check the square-ness of an end face with the longitudinal axix of acylindrical piece, rotate the piece in Vee blocks asshown in figure 41, noting the amount of deviationof the reflected retitled. To check a rectangularpiece, turn on each side and note the amount anddirection of each deviation

5.6.7 APPLICATION OF THE INSTRU-MENT TO THE INSPECTION OF OPTICS.All exterior and interior sur@ces of optical prisms,wedges, windows and mirrors can be convenientlychecked by all the methods indicated for metalparts. The prime advantage of using an auto-collimator rests in the fact that internal reflectingsurfaces may be checked, For example, the 90”angle of a right angle prism may be checked by themethod shown in figure 42. The auto-collimatorwould be directed at the hypotenuse face. Anoptical flat is not needed here as in the case wheremetal parts are checked and therefore ccmtact erroris eliminated. For an error of 8 in a 90” angle, an

angle Of 4hTfJwill be returned to tbe instrument,where N = index of refraction of glass Care mustbe exercised relative to the retitles used by variousmanufacturers of auto-collimators, ina.snuch assome are compensated to allow for the double errorand others must !Wcompensated for by the operator.

5.6 OPTICAL TOOLING. The use of telescopes,collimators, auto-collimators and various accessoriesin a combined approach to dimensional inspectionis referred to as opticai tooling. It could also bereferred to as the art of applying the principle ofsurveying and optics to dimensional inspection.While generally employed in the inspection of largeproducts, it is flexible enough tO be applied tOalmost any type of precision measurement job. Forthe purpose of this handbook, optical tooling may

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vary from a simple alignrneit telescope and targetto a ‘massive layout involving several telescopes, ~~tooling bars and stands, targets, etc., covering aconsiderable area.

5.7.1 TYPES OF EQUIPMENT. A inriedselection of optical devices and accessories areavailable. The more common will be listed here.

5.7.1.1 The Alignment Telescope. Theaiignmenttelescope (see figure 43) is one of the most basicinstruments that is used in optical tooling: Its

main. purpose is to establish a precise reference lineof sight, However, with the usc of various acces-sories listed under,5.7.2,;it may perform manyother function’s such as measurements; auto-Collimation; projection; etc.5.7.1.1.1 Description. Thetelescope mqunt(ttibe

which holds the lens system) is made of hardenedstabilized tool steel with a hard chrome surface.The outside di~eter is ground to a standard2.2498 inches and is concentric with the opticalaxis of the instrument. Most alignment telescopes

contain built-in micrometers for measurement ofvertical and horizontal displacement. The microm-eters are direct reading to .001 in., numberedevery .OIO in. andhavea range of from .Oto +.050in. Thereticle may beglasswith acrosslinepatternor simply cross-wires. An eyepiece is provided tocompensate for variations in human eyesight andfor keeping the reticle in focus when the main focusof the i@mment is changed. A built-in autc-reflection target is usually provided on the rearface of the objective lens.

5.7.1.1.2 Magnifying Power and Range. Basic-ally, it is a variable power telescope with a resolutionof about 3 seconds and a magnification of approxi-mately 4X. to 6X at minimum focusing range andfrom 30X to 60X (depending on manufacturer) atinfinity. Focusing ranges vary with the manu-facturer. Most instruments have a focusing raugeof about 18 inches to infinity, with at least one typecapable of focusing all the way from infinity down toactual contact with the end of the telescope.

5.7.1.2 The Alignment CoUirrwtm. The align-ment collimator as used in optical tooling is a targetinstmment for setting up a precise reference lineof sight, as opposed to a viewing instrument, i.e.,it does not possess an eyepiece. It is also used forchecking and adjusting other optical tooling instru-ments. See figure 45.

5.7.1.2.1 Description. The alignment collimator

consists of a hardened stabilized tool steel tubeground to a standard outside diameter of 2.2498 in.,concentric with the optical axis. A displacement oralignment reticle pattern is centered on the rear sur-face of the collimator objective lens. An infinity

or titlt reticle is placed at the principal focus of theobjective lens, generally 10 inches, sce figure 46.The tilt reticle is usually graduated every 30 secondsin four directions from zero as in figure 47. Thecenters of tbe tilt and dkplacement retitles are onthe optical axis of the instrument. The tilt reticleis illuminated by a low voltage, removable lamp unit.

5.7.1.2.2 Operaiion. In operation, the tilt reticleis illuminated and the rays of light from this retkleemerge in a parallel beam. If an alignment tele-scope is focused at infinity and placed in this beam,the tilt reticle of the collimator can be made toappear in the telescope. The graduations on thetilt reticle allow a dkect reading of the angle thatthe optical axes of the collimator and the telescopemake with each other. By superimposing the tiltreticle of the collimator onto the telescope reticle,

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5.6.1.3.2 The Optical Tram-it Square. The transit

quart is also basically an alignment telescope in ayoke. The vertical axis in this case is solid; measure-ments are taken from a vernier and scale attachedto the tooling bar and carriage, The horizontal

“, axle of the telescope is hollow and sealed at each

FIGURE45, Alignment coUimator. end with windows; one window is clear, and theother is optically flat and partially coated on theinside surface to make it a semi-reflecting mirror.

collimation is accomplished; that is, the optical The mirror, as in the jig transit, is exactly parallelaxes of the two instruments are parallel but they to the telescope’s line of sight. Auto-collimationmay be displaced by an “unknown amount. and auto-reflection are performed in the same5.7.1.2.3 CoWnea~iom If the telescope ‘is now manner as with the jig transit to establisb a right

focused on the collimator displacement reticle, the angle line of sight One advantage of the opticalamount of displacement can be read dkectly and transit square is that the ho60w axle design permitsthe two instruments can be brought into collineation a series of instmments to be used on the same optical(common optical axes) thereby establishing a reference line.straight reference line of sight between the two 5.7.1.4 The Tilting LeueL The tilting level is aninstruments from which other lines of sight or ~‘ extremely accurate instrument for precise levelingmeasurements may be taken. See diagram, figure in optical tooling, Basically, it is a 30X telescope4s. with a resolving power of 4 seconds. The focusing

5.7.1.3 The Jig Traw”tand Opticul Transit Square. range is from 6 feet to infinity. It provides anThe jig tranait in F@e 49 and optical transit erect image, wbichis atime-saver in that the opera-aquare are two somewhat similar instruments de- torisnot subject to mistakes indirection. A2j4Xsigned to do practically the ame thirig, which is: coincidence type split bubble level is mounted

(a) To establish a precise right angle plane exactly parallel to the line of sight. A tilt of onewith the optical reference line of sight sscond of arc (approximately .0015 in. at 25 feet)determined by the alignment telescope.

(b) To take accurate measurements of linearis plainly visible in the level window. A tiltingwheel under the eyepiece is used to set the telescope

dimensions when used with a tmiing bar level. The tilting level should be equipped with anand other accesecmies. These two in- optical micrometer m that accurate readings maystmments do have different featurss be taken with respect to the leveling points. Seeand will he dkwussed separately. figure 50.

5.7.1.3.1 The J@ Tram”t. The jig transit is , 5.7.1.5 Targets. There is a wide variety of com-

basically an alignment telescope in a yoke. The mercial targets available, ranging from simple

yoke is constmct-ed so that the telescope may be cross-lines to elaborate etched grids from which

rotated 360° in a vertical and horizontal plane. In displacement can be read directly. F]ve types willsome makes the yoke has a hollow vertical axis be discussed here, as shown in figure 51,through which the telewops may view a scale placed 5.7.1.5.1 Alignnwnt Targets. Alignment targetson the tooling bar (see par. 5.7.1.6.1), in others, give a point of reference and usually consist of pairedthe readings are taken from a vernier scale attached black lines of different thicknesses and spacing. Itto the carriage mount. Provision ‘is made for has bsen found that an obssrver can center a tele-mounting an optically flat front-surface mirror on scope reticle in the white space between two blackthe horizontal axle of the telescope, exactly parallel lines much more accurately than he cm place theto the tele.stops’s line of sight. This permits ,the reticle on a single black line. The observer choosesuse of autc-collimation or auto-reflection (&e par. the set of lines with the smallest spacing that will5.7.2.2) from it ‘to eitablisb a precise right angle’ still clearly show white spaces on either side ofline of sight. The telescope has a focusing range center.from 8 inches to infinity. Magnification varies from 5.7.1.5.2 Displacement Targets. The displace-20X at 8 inches to 30X at infinity. The field of view ment target gives a point of rsference and also hasat infinity focus is 1“10’. horizontal and vertical scales to measure dkplace-

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ments from the line of sight up to .300 inch. It isusually mounted in a hardened stesl ring.

5.7.1.5.3 .4u@Re@ctiom Y’argek. The auto-re-flection targets are used on the front of sighting

telescopes to give a reference point on the line ofsight for autc-reflection. The paired-line principleis used, but the pattern is based on somewhat widerspaces than the alignment target.

5.7.1.5.4 Mirroi’ l“argds. Themirror. target con-sists’ of an alignment target pattern cut in the silver-ing, of ,? front surface mirror, It ii used to give apoint of reference and also, by auto-reflection andauto-collimation, to control the tilt of the object onwhich it is mounted, The pattern is modifiedbecause it is illuminated from the back and thereforepresents lines of light color against a dark back-ground”.. 5.7.1.5.5 Double Line Targets. Targets areof the

paired line principle and are engraved on whltiplastic plaques and fiUed with black. The w~lte

spacing crmbe from .005to .100 inch. By choosingtarget line spacing on the bisis of the range at whichthey will be used, targets at key points indicateproper tolerance. Distance and’ line spacing arepredetermined so that equal wh]te areas on eitherside of centerline will show that measurements arewithin tolerance.

‘IWing LueL

5.7.1.5.6 If it is desired, aspecial purpose targetmay be designed giving limits of dkplacement forquick inspection or reading various functionsquickly. Cost canincrease quickly asthe markings

become more complex or highly accurate, so pru-dence is indicated. On short production runs orthose of lesser accuracy, improvised target.s may beemploywl.

5.7.1.6 Tooli~Bars ati Znstmment Statis.

5.7.1.6.1’ Horizonta’’’Tooiing, Bur A“hOTizOntal..tooling bar basically consists of an aluminum trackof box+ike cross-section upon wh]ch is fastened afull Iength steel index bar having precision drillbushings spaced every 10 inches. A carriage, onwhich an instrument (such as ,a ,jig transit) ismounted, traverses tbe length of the baron machinedvmysandis capable of being locked in place. A teninch scale with a precision ground plug fits into thedrill bushhgs of the index bar, which iri conjunctionwith a vernier on the carriage or a sight through themount, permits horizontal linear meamirements to.001 inch accuracy. The height of the tooling barcan be regulated by adjustable mobile stands.Tooling bars come in various lengths, from 10 feet’to abotit ,30 feet and indwidual sections can be con-nected to give any desired length. See figure 52.

AGO 10117A 103


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a, Alignment,Jarget. b. Dkple.cemmttarget. c. Auk-reflectiontarget. d. Mirrvrtarget. B. D.mbk-lim target.

,. Fmum 51. Tav@a.,

5.7.1.6.2 Ver~icd ?’ooU?WBar. The vertical tool-ing bar in Figure 53 makcc it ~ible tb meaaiwelinear dutances in tbe vertical dimension to anaccuracy of .001 inch, me construction is akmytthe ~me as the horizontal bar, except that thecarriage is counter-balanced’ for eme of movementand is also spring-loaded to assure continual contactwith the ways. The bar is supported by thq+e radialarms, each of which contains crmtem and leveling~rews. Two levels, mounted at 90° ta one another,indicate when the tooling bar @ vertical, Measure-

ments are taken in the same manner ti” on the hori-zontal tm6~ng bar.

5.7.1.6.3 Instrument! Stands. I@rum@ standsarc used to provide a ~ld, mobile support for almostanY ,tYw of optical ,ititrument~ The height is

adjustable from about 44, inch:s @ 72 inches bymemcof a capstan wheel with rack and pinion. “Aclamp locks the telescoping cylindrical column at

tbe desired height. A crow-slide may be mountedon top “of the center column ta permit a limitedlateral adjustment (2?4 in. to 4% in. depending onmanufacturer). The cross-slide is fully rotatablethrough 360?. The stand is supported by threerndial arms, each of which contains caater.s andleveling screws. See figure 54,

5.7.2 ACCESSORIES.5.7.2.1 Optical Micrometer. An optical microm-

eter as in figure 55, is an attachment that may beused on TMing Levels, Jlg Transits and OpticalTransit Squares for very, preciee measurements,alignment, or leveling, It works on the principleof refraction of light rays. When a Iight ray entersa dkc .of optic@ glnas with flat parallel faces, at anyangle other than perpendicular, it is refracted orhcnt a predictable amount accordhg to the law ofrefraction, When the ray leaves the glwss, it isagain refracted so that it proceeds at its original

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FIwm 53, Vdicd twli~g bar.

angle, but displaced a certain amount, The opticalmircometer takes advantage of this property of lightby controlling the amount of tilt of disc of opticalglaes with a graduated drum. When the drum isturned a precise amount, the line of sight is movedparallel b itself a proportionate amount as in figure56. The micrometer drum is graduated directlyto .001 in,, numbered every .010 in. and has arange of from .0 to &. ICK3in. The micrometer maybe positioned to meaaure either horizontal or verticaldisplacement.

5.7.2.2 Ardo-CoWnution Unit. By illuminatingthe reticlee of Alignment telescopes, alignmentcollimators, and transits, auto-collimation and auto-refhxtion is mnde possible, thereby incensing theusefulners of theee instruments. The various manu-facturers achieve thm result in different ways. Insome instruments, the unit is built in but the light

source is removable. In others, figure 57, the unitis complete with an eyepiece that is interchangeablewith the eyepiece of the instrument. Most of theunits have” a rheostat for controlling the amount oflight to the reticle.

5.7.2.2.1 .4uto-R@ection. Auto-reflection is usedto position a plane or surface perpendicular to areference light of sight. An instrument with anauto-reflection target on the end (mounted on thebarrel or on the inside surface of the objective lens)and an auto-collimation unit or other means ofilluminating the reticle, is needed. The instrument,with its reticle illuminated, is sighted into a mirrurplaced at some convenient dis?tance and focused onthe reflected target image, If there is an errur in theperpendicrdarity of the mirror to the line of sight,the target image will be dkplaced with respect tothe instrument’s reticle. By manipulation of themirror, the target image may be moved until it is

AGO 10117.4 105


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FICUBE55. Optical micrmneter.

centered oh the’ reticle. The line of sight “is now.reflected back on itself, proving perpendicularitybetween the rr@ror and the line of sight. Theprinoi~e of auto-reflection is illustrated in figure 58.

5.7.2.2.2 .4u&-COWmatiom Autu-collimation issimilar to auto-reflection but more accurate. . Inauto-reflection, the inatruqent is focused at a. finited~tance, i.e., twice thedktance from tbe target tothe mjrror, therefore any observational error incentering the target image on the reticle is equivalent

DISC LENS DRUM

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FIGURE 56. Principle of the opticalmicrometer.

FIGURE57. .4u{c-collimation unit.

to a Perpendicularity error of tbe mirror and is afunction of tbe distance from the instrument to themirror. In’ auto-collimation is in auto-reflection,

the instrument’s reticle is illuminated and tbe mirror

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ic placed at some convenient distance but the in-strument is focused at infinity which makes it anauto-collimator, bringing the instrument’s reticleinto focus, Sighting into the reflection of theinstrument’s reticle is the same aa sighting intoanother collimator and the distance to the mirroris no longer a factor as explained previously in par.5.6.4.

5.7.2.3 Protection Eyepiece, .’l%e projection uuit(shown in figure 59) is used in place of the standardeyepiece of traueits and telescopes so that thereticle pattern may be projected, into the objectbeing worked on. It is generally desirable to use aprojection reticle that hac been specially designedfor p~jection. This reticle haa fine lines for C1OSCwork and heavier lines for longer ehota. Reticlepatterns can be projected 25 feet or more. Sometypes of projection units have a device which per-mite projection and normal vidon through theinstrument. ‘

5.7.2A Right Angle Eyw”ece. The right angle,or elbow eyepiece, ie interchangeable with theeyepiecee of most optical tooling inatr’umerits. ‘Th”eyepiece ie used for very low’’sit-ups m wor!+ng cloceto wails, columns, or other obstructions. It alsomakes it ~ssible to w the transit to convenientlytake sights at any high angle, including dircctiyoverhead., The right angle eyepiece is fully rotat-able throu~. 360? foi sighting from any perpendi-cular angle, It is also available ca a combhationauto-colliinntion projection and right angle eyepiece.

6.7.2.5 Levels. Levels are wcd to eatabliihhorizontal planes or lines of sight in conjunction withtelescopes and other instruments. There are threebaaic types:

5.7.2.5.1 Bull’s eye or circukw hvel, Uced to

rough level an instmment bcee or fixture in twoplancaat one time,

5.7.25.2 Tubular kuel. Used to cemi.precti]onlevel an imtrument base, an instrument, or a fixturein one plane at a time.

5.7.25.3 Coincikmce kuet, The halves of each endof a split bubble, figure 60, are attached (W viewedthrough a pricmatic system).

(8) Uccd to precti]on level an inctmment or afixture in one plane at a time.

(b) Accurate to withh 1 or 2 seconds of arc.(c) Level cctting is indicated when ends of

bubbIe are h coincidence ac in 3 offigure ML A striding level, w picturedin Figure 61, is a coincidence level that

108

clips on the barrel of an alignment colli-mator or alignment telescope for preci-sion leveling. It also containc a bull’seye level for rough leveling and a rotatingviewing mirror.

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5.7.2.6 Optical Square. The optical square is aninstrument which, when used in conjunction with analignment telescope, will establish a plane perpendi-cular to the telescope’s line of sight without the needfor auto-collimation or auto-reflection. It comdstsof a penta prism (a penta prism has the ability toturn a line of sight exactly 90? even though it is notaccurately aligned itself) mounted in a sphericalhousing. The square hns a unique feature in thatit has both a front and a side aperture, permittingtbe observer’s line of sight (by manipulation ofaperture covers) to he turned through the 90° angleor to pass undeviatcd through the instrument. Thkfeature allows the basic line of sight to be checkedwhile the optical square is in place. The sphericalhousing, when seated in a special cup mount, per-mits the line of sight to be fully rntatable in thevertical plane for 360?. See figure 62.

5.7.2.7 Mirrors. Mirrors play an important partin optical tmoling. Their main use is in auto-colliia-tion and autc-reflection to ectablisb a plane perpen-dicular to a line of sight. They m5y also be used tocheck the perpend]culafity of a surface to a line ofsight or to establish the axis of rotation of shafts,spindles, etc., so that other parts mny be aIigncd withthem.

I 5.7.2.7.1 A.de Mirrrm An axle mirror ii a frontsurface mirror that is optically flat within % wave-length of light (.0000058 in.) and can be screwd oneither end of the telescope axle of a jig transit.It is adjustable to make it parallel to the telescope’sline of sight.

5.7.2.7.2 Magnet Black Mirror. A circular frontsurface mirror from 2 to 4 inches in dlametei whosereflecting surface is optically flat within % wave-length of light, One to three magnetic feet arecemerrtcd to the back of the mirror. Their contactsurfaces are ground parallel to the mirror surface.

I

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I FIGURE 62. O@icd qwzr.

When the mirror is not in acti~al uss, an iron or st.eclkeeper should be placed over the rnngneta to retaintheir magnetism.

5.7.2.8 ‘Poofing ‘1’rqrc8. An important problemin optical tuoling ic the difficulty of making precK1onmeasurements over considerable diatancss (2O ft.

to several hundred ft.). Optical Tooling Tapesfulfill thu rcquiremeti. They m-c made of steel,

Vg inch wide and about .008 inch thick, The gmdua-tions are ,006 inch wide, spaced at 10 inch intervalsand are clearly vidble under the magnification of ajig trancit. Inch numbers are printid beside eachgraduation. Tooling tapes are available in 20 ft,50 ft, and 100 ft. Iengthe and can be made in anydesired length up to 300 feet.

5.7.2.8.1 A certificate is furnished giving the ten-sion at which the overall length will be comcct at68?F, Tapes 100 ft. long or la require about10 lbs. tension and those over 100 ft. long rcquirsabout 20 lbs. When the correct tsmcion is applied,no graduation will vary mom than .005 from itstrue position and no 10 inch length will vary momthan .003.

5.7.2.8.2 A temperature -correction rrced not be

applied when the tape is used on a machhre wl,steel jig or other structure, since the tape will assumethe same temperature as the structure. But if thetape is used to determine an exact dk&mrce, thefollowing correstionc must be applied:

Change in lerrg%h= (LJ (CJ (TJ

Where L. is the original length in inches, C. ic thec“mfficient of linear expansion (.00000645 in. perdegree F.) for steel and T. is the temperature changein degrees from 68°F.

5.7.2.8.3 The temperature correction noted aboveis applicable to all dnensional inspection equipment any time there is a temperature differentialbetween the oblect being gaged and the inspectionequipment. The onfy variable possibly being theco@icient of linear expansion which varies slightlywith the clifferent t~es of steel. The difference isusually negligible however and may be safely takenas the figure uccd above.

5.8 OPTICAL PROJECTION

5.8.1 PRINCIPLES OF OPTICAL PROJEC-TION, Optical projection conskts of the projec-tion of a sharply outlined and magnified shadowsilhouette of the part being inspected u~n a trans-lucent screen. This is cccompliched by placing thepart within an optical system consisting of a light

I AGO 101I7A 109

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source, condensing lens, obiective lent and screen,sc in figure 63,

5.8.2 GENERAL REQUIREMENTS FOR OP-TICAL PROJECTION. The optical system of aprojector requires careful design and construction.The more important requirements are:

(a) The image must be sharp on the screen

and there must be no furmsing errors,(b) There must be no distortion of straight lines

into curves.

(c) There must be no astigmatism, that is, nounequal definition of the image causedby horizontal lines being out of focuswith the vertical lines.

(d) There must be no color fringes.(e) Tbe magnification should be capable of

variation,(f) Tbe image on the screen should not be

reversed or upside down.

(g) Tbe light source should give sufficientillumination to establish. a high degree ofcontrast between the field and tbe partsilhouette.

5.8.3 REQUIREMENTS FOR OBTAININGMAXIMUM IMAGE SHARPNESS.5.8.3.1 Positioning of the pd. A sharply de-

fined image can be obtained if the d~tance from thepart to the objective lens is equal to tbe focallength of tbe lens. A small increment of adjust-ment, say l~t inch sdded tm the focal Iength,” shallbe allowed h overcome any minute variations thusproducing maximum sharpness of tbe projectedimage. In obt,ainingrnaximum sharpness of tbe pro-jected image of a comparatively thick object, thepoint of focus should be a point at the edge of the partnearest to the objective lens. Gaging of thick partsby direct projection should be avoided whereverpossible.

5.8.3.2 Necesti”t~ for Paraltet Light. The projec-tion of a parallel beam of light emanating from thecondencer is’of major importance in obtaining acharply defined image. If non-parallel light raysare emitted from the condensing lens, the sharpnessof the image on the screen will decrease as the thick-

ness of the part increases. The majority of com-mercially manufactured projectors or comparatorshave condensing systems that emit light rays whichford practical purposes approach true parallelism.

5.8.3.3 Selection OS Propsr Magnijfcation. Themagnification of the projector is the ratio of thelinear size of the image to the linear size of the object.

AGO 1011?A 111

The common commercial magnifications are 10X,20X, 31)4X, 50X, 62%X, and 100X. It is notalways po~ible or desirable to completely fill thescreen for a given magnification. The line ofdemarcation of the image should be sharply differen-tiated from the surrounding field. If the sharpneccis not of tbe desired intensity, the magnification maybe high. Therefore, the lowest magnification consis-tent with tbe size of the component and tbe magni-tude of tbe tolerance should be used.

6.8.4 OPTICAL PROJECTORS..5.8.4.1 General Feature8. An optical projector

may be uced for comparison or for measurement.If used for a comparison, the image is compared withan outline drawn on the screen. When uced formeasurement, the projector incorporates the use ofa lateral table travel or a cros-slide table which

can be moved in a horizontal or vertical dbection orbotb and at right angles to the beam of light. Forlinear dktanc:s up to one inch, micrometer heads areprovided. For measwements over one inch, pr-evisions are made in the table for the use of gageblocks.

5.8.4.2 Types. Projectors can be classified intotwo types by usage; gaging and measuring projectors.A gaging projector ii used to project an image forcomparison purposes against an outline laid out ons screen chart and is intended for production gaging,No actual measurements are performed, but a deter-mination is made as to whether the part lies within

specified limits. The measuring projector finds itsuse mainly in the metrology Iaboratury, the toolroom, and in production control, and is not generallyadapted to the final inspection of parts in quantity.See figure 64 and 65.

5.8.5 STAGING FIXTURES.5.8.5.1 General Design Features. The holding or

staging of a component determines the degree ofaccuracy obtained from optical projection, Tbefunction of the staging fixture is to bold the compon-ent at a fixed distance from tbe objective Iem withthe focal plane of the component perpendicular toth’e center line of the lens system. The componentmust be positioned in the horizontal and verticaldirections in order that the desired outline willalways fall in the came position with relation to tbescreen. The design principles of gaging and stagingfixtures are similar. However, it. is not necessaryto maintain the high dimensional accuracy commonto gages in designing staging fixtures. The accuracyrequired is achieved by the accuracy of the screen


MIL-HDBK-204

FIGURE 64, Mea-swing pmjecfor.

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FIGWBE 66-C!ontimmd,

layout and the method of setting the staging fixture

with reference to the screen. A simple setting checkmay be provided to aid in setting up the stagingfixture.5.8.5.2 Types of Staging Fixtures. Staging fix-

tures may be classified into three distinct @egories:Compensating T~ePermanent Aligned TypePosition Locking Type

5.8.5.2.1 Compenmting Type. The compensatingtype of fixture is used with optical comparatorswhich have no adjustments for either focus urpositioning of the component on the screen, Inthk type of Iixture, all the neces.%ry adjustments areincorporated into the fixture. See figure 66(a).

5.8.5.2.2 Permanent Aligned Type. The per-manent aligned type of tixture is clampud to thetable of the comparator and is positioned withreference to the low lens syskm by means of slotsor other locating points. See figure 66(b).


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5.8.5.2.3 Position Locking Tvpe. The positionlocking type of,fixture is used with optical compara-tors having adjustments for focus and positioningof the part silhouette on the screen. Usual]y aseries of part dlmensiorral features are checked withthis type of staging fixture. The part is firstpositioned in a movable element of ‘the’ fixture andthen, in order to view another portion of the part onthe screen, repositioned by moving the element withrespect to the base of the fixture. In auother typeof multiple positioning fixture,. tbe part is actuallymoved with respective to the fixture. See figure66(C).

5.8.5.3 Indirect Obseruaticm; In a fixture havingprovisions for indirect observation, an element ofthe hoIding fixture which is either fixed or movableis stopped against the surface of the part that is tobe gaged which will be out of focus with the screen.An extension of this element which is located in sucha manner that it is in focus, then shows the relativeposition of the gaging surface on the screen.

5.8.5.4 Auxiliary Gaging. Auxiliary gaging maybe incorporated into the Staging fixture by use offlush pins or dial indkmtori to take care of additionaldimensions which cannot ,be gaged by opticalprojection,

5.8.6 SPECIFIC DESIGN INSTRUCTIONS.The following procedure should be followed in thedesign of a staging fixture.

1, Determine the part dimensional features to begaged by optical projection methods.

2. Determine whether optical projection is prac-tical and will obtain the desired results.

3. Determine how part is to be held in the stagingfixture.

4. Determine focal point or plane.

5. Select the proper magnification keeping inmind the part tolerarice and size of image relative toscreen.

6. Plan the actual design.

7. If a compensating type of fixture is beingdesigned, check that sufficient adjustments are pro-vided in the 6xture. In the position locking type offixture, check to insure that the optical, comparatorhas sufficient adjustment to line up the fixture withthe ccreen.

8. Check focal clearance.

9. Check complete design for proper functioning.

10. Design a setting check.

114

5.8.7 SCREEN C’HA RTS.

5.8,7.1 “General Features. The screen chart showsthe magnified image of the part and the tolerancelines in which the image shall fall. The screen chartmay be prepared on translucent Engineer’s glass,.plastic, or paper. Permanent master layouts are

prepared on Engineer’s ground glass. On screencharts requiring greater accuracy, the layout isscribed on scribing glass.

5.8.7~2 Diflerent Tvpes of Screens. In ordreingscreens, it should be noted that there are two typesof screens:

Overscreen (or Screen Chart)Replacement Screen

5.8.7.2.1 Owrscreert. The Overscreen type of

scrccn has the layout on the side of the glass awayfrom the inspector. Thk type is made of either plainor ground glasx, and is placed over the regularground glass screen furnished with the comparator.

5.8.7.2.2 Replacement Screen. The replacementtype of screen has the layout on the side of the glassfacing the inspector, This type of screen is furnishedin ground glass and is used in place of the .origimdwh]ch must be removed from the comparator.

5.8.7.3 Accuracy. Actual tests have shown thatwith reasonable care cbirts can be laid out by draft-ing room methods with an average error of .005. Theactual error ,is computed thus:

Actual Error = Deviation from basic size onChart divided by magnification.

5.8.7.4 Methods of Screen Layout and Checking.Layouts should first be pencilled and then tracedusing full strength ink. Care should be taken illmaintaining uniform th]ckness of line and in blendhgof radii and corners. The following suggestions mayaid in producing satisfactory layouts:

(a)

(b)

(c)

When broken lines are required, it is sug-gested that the line be ruled in completelyand then parts of the line erased. This willinsure a straight and uniform line.In drawing circles and rad,i, a good non-slipping center for divider or compaxc pointsis made by attaching two or more smallpieces of scotch cellulose or draftsman’stape, one upon the other to the surface ofthe layout,For greater accuracy, tit a set of points tothe jaws of a vernier caliper or special gageblock accessory for the purpose of measure-ment.

AGO 10117A


(d) IrI the lower magnifications, many of the

commercially manufactured optical com-parators project reversed and invertedimages on the screen. This should be takeninto consideration before preparing thescreen layout.

5.9 INTERFEROMETRY. As mentioned in

paragraph 5,1.1, light appears to travel in waves andtherefore produces certain effects that are quitepredictable. Referring to figure 67, the top figurerepresents an idealized light wave. One wavelengthis measured from where it begins to where it startsto repeat itself. In the middle figure, if two wavesof the same wavelength coincide, they produce a newwave which is equal to their sum. In the bottomfigure, if two lightwaves of the same wave-length are out of phase by ~ of a wavelength, they

—— ——-===1FIGURE 67. l’~operties of lirhtmaws,

FIGURE68. I%nluctimof inkrferencebanda,

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will cancel themselves outand darkness results, Theproblem here is to accurately displace the two wavesone half wavelength, when this is a distance of

.0000108 on the average, In interferometry, thevery accuracy of the pieces being measured sets upthis phenomenon,

5.9.1 PRODUCTION OF INTERFERENCEBANDS. When an optical flat is placed upon aprecision finished reflecting surface, it is almostimpossible to place it in absolute contact since a thinwedge-shaped air film will always be present. Thespacing between the two is in millionths (assumingthat tbe precision surface is not perfectly flat) so thisspacing liesin or near the range of the wavelengthsof light. Therefore, if light is passed through theflat and reflected partially from the lower surface oftbe flat and partially from the precision surface, thetilt or displacement between the two can produce thephase shift necessary to cause interference. Refer-ring to figure 68, the dark bands are producedwhereever the flat-reflected portions of waves arecorrectly out of phase with the inspected surfacs-waves. This occurs whenever the distance betweenthe reflecting surfaces is one-half a wavelength or itsmultiples, Using sunlight or an ordinary incan-descent bulb, the fringes will be colored like smallspectra and be rather wide. Therefore, a mono-chromatic light is generally used. Itisa source thatproduces light of nearly one particular wavelengththat is obtained by exciting the gas of a particularelement with an electric current (somewhat similarlytoanordinary neon sign ligbt), Helium isused mostgenerally for its combination of low price, purity, andavailability. It produces a wavelength of 23,1323microinches and has a greenish yellow color withgood sharpness of the bands. Krypton, Sodium,Cadmium and Mercury arealso”sed asmonochro.matic sources.

5.9.2 INTERPRETATION OF INTER-FERENCE BANDS, When the flat is placed incontact with the work, bands immediately appear.They mayassume many varied patterns, dependingupon thesurface properties of the work. If the workis nearly fiat, the bands will bestraight andparallei.If tbe work surface is uneven, the bands will show itby assuming the role, of contour lines just like thoseon maps. First, the reference point or point ofcontact between flat and work must be established.This is done by pressing down on the flat at a pointdirectly above an edge that runs parallel to thegeneral direction of the bands. If they remain the

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same distance apart, this edge contacts the flat, Ifthey tend to spread apart, the opposite edge. is incontact. If they appear to be spaced irregularly,then tbe point of contact lies within the surfacesomewhere. Since each band represents % wave-length of light, and if helium light is used, each bandthen represents 11,6 millionths of an inch distanceof the flat from the work, so. that 3 bands equal 35millionths and so on.

5.9.3 DETERMINATION OF .FLATNESS. ~The bands and their relative arrangenient can beused to assess tbe flatness of a surface. Since eachband is representative of a fixed distance from theoptical flat to the test surface, if the surface is notflat the lines will tend to outline its irregularities inthe manner of contour lines on a map. For example,if a surface is faintly spherical, the bands would be aseries of concentric circles aroundthe point of contactwith each successive circle a little closer to the oneinside it. If the surface W3S faintly cylindrical, a

series of arcs would appear. If a true cylinder, thearcs would be equally spaced, but if it were uneven,the arcs would be spaced unevenly. Finally, awarped surface would give an effect such as figure 69,To utilize this effect, tbe point of contact is first.located as mentioned in 5.9.2, Now, rememberingthat the optical flat is flat within one or two mil-lionths across its diameter and the foregoing di~cussion of contours, the accuracy of the test surfacemay be asseseed. It is most easily done by visualiz-ing an imaginary scale on the image of the bandswith the zero point at the point of contact betweenflat and work. The scale should consist of equallyspaced divisions which in nearly all cases should beequal to the distance from the point of contact to thefirst band. If it is dificult to visualize, a small layoutcan be made to place on the flat as an aid in estimat-ing spacing. If the scale divisions are fairly wide,they should be mentally sub-divided into tenths forconvenience. If the surface was flat, the bands andscale divisions would coincide and also there wouldbe relatively few bands. If the surface is irregular,there will be many more bands irregularly spaced.The bands will be close together on slopes andfurther apart on” level or nearly level spots or atpoints of contact. See figure 70. If it is difficult topick out the actual deviation (too many lines),transferring the point of contact to the adjacent sideof the piece will give a d]fferent pattern to beevaluated. It may have fewer lines and thus. bemore easily interpreted.

5.9.4 MEASUREMENT OF HEIGHT.Height may remeasured byinterfemmetry in twoways, either by comparison with a known height, orby direct measurement.

5.9.4.1 Measurement Height by Comparison. Inthis method, a precision height standard of knownsize such as a gage block, which is very close to thesize of the height to be determined, is compared withthepiece to remeasured by placing an optical flaton both surfaces, Thetilt orangle assumed bytbeflat due to the height difference can be measured by

counting the bandson the Iower block.

5.9.4.2 Absolute Znterferometry. Absolute inter-ferometry is a method of measuring the length ofgage blocks directly using wavelengths of mono-chromatic light as natural and invariable units oflength. This is accomplished in two ways. Thefirst and original method is to produce bands on theinspected surface, then faise the platen until it is atthe came level, and count the bands in between.

FImmm69. Delemninalwnofj?atness,

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116 AGO 10117A


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This can be accomplished vicually or automatically

by an electric, eye scanning device in the se-calledfringe-comit interferometer. The eccond methodutilizes a dispersion prism toresolve the light from acadrnkmn discharge tube into monochromatic radia-tions of several different colors (usually red, green,and blue), tbe wavelength of each being preciselyknown. Two groups of fringes from eachcolor inturn are seen when the rays are directed at the gageblock andthebaccplatcto which tbegage block iswrong. The length of the gage block is equal tO a

I

IAGO10117A

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specific number of half ‘wavelengths Plus the frac-tional displacement between the two groups offringes. The amount of displacement is read frominternally located optical micrometers, This isrepeated for each color, and from the measurementof these fractional dkipbcements it is possible, by amethod known as coincidence, to determine theerror of the gage block from its nominal length. A

special slide rule is used to assist in this computation.Finally, corrections must be made for temperature,humidity, and b.arometric pressure.

117


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CHAPkER 6. NON-DESTRUCTIVE TESTING6.1 INTRODUCTION. Non-destmctive testing

is an important part of the Acceptance InspectionEquipment Program. Even though a part ,rnay bedimensionally acceptable, it may have surface cracksthat are invisible to the naked eye or sub-surfacedefects such as blow-holes or segregations. Theseflaws, whether surface or sub-surface, may cause the

part to fail in ccrvice when placed under a normaloperating load. ‘It is the object of non-destructivetesting to discover these flaws in the most economical

manner without damage to the part in any way.Non-destmctive tests are specific. Generally, theyreveal only the specific kinds of defects and condi-

tions for whose detection they were designed,Consequently, they must be selected in accordancewith the specific material conditions and the job tobe done.

6.1.1 PROBING MEDIUMS. Most non-de-structive tests depend upon a probing med]um forthe detection and transmission of information aboutthe object under test. This medium is supplied byan external source such as x-ray tube, magnetizingcoil, or ultrasonic transducer. The probing mediummay be distributed throughout the test object (broadx-ray beam), or it may be concentrated into a narrowbeam (ultrasonic testing). The depth of penetrationof probes varies greatly. X-rays may pas throughseveral inches of steel, whiIe ultrasonic waves havedetected dkcontinuities through as much as 50 feetof steel or 300 feet of concrete.

6.2 LIQUID PENETRANTS. Liquid’penetrantsis one of the oldest methods of non-destructivetesting. Because the method relies on a penetrantseeping into a discontinuity, it is obvious that it is

applicable only to surface defects or tjubsurf acedefects with surface openings. It is applicable to allmaterials, magnetic and non-magnetic, ferrous andnon-ferrous, except those materials that are of aporous nature.

6.2.1 BASIC PROCESS, Basically, it is a verysimple process. First, a liquid dye penetrant is

applied to the surface of a part. It is then permittedto remain on the surface for a period of time, duringwhich it penetrates into any defects open to thesurface. After the penetrating period, the excesspenetrant is removed. Then a developer is appliedto the surface, which acts as a blotter and draws outa portion nf the penetrant from the defects, causingindications to be formed which are much wider than

the defects with which they are associated. Theinspector then views the part and looks for thecccolored indications against the background of thedeveloper. See figure 71.

6.2.2 VA RIA TIONIS. There are several vmia-tions to this basic proceac:

(a)

(b)

(c)

(d)

(e)

6.2.3

The dye penetrant may be applied to the

part by dipping, spraying or brushing.

The penetrant may be a brilliant, ffuores-scent dye. If this type of dye is used, thepart is inspected in a darkened area under“black” or ultraviolet light. Any cracks ordefects show up ac a brilliant yellow-greenfluorescence.

The penetrant may be water-washable, ex-cess penetrant being removed by a coarsewater spray, or the penetrant may be post-emulsifiable, in which case an emulsifier is

applied to the part after the penetratingperiod. After a short time, the penetrantmay be removed by a water spray, Thepost-emulsification process is more sensitivein detecting very fine cracks,

The developer, which is a light-colored,powdered material, may be applied dry bydusting or blowing it on the part, or it maybe applied as a solution by dipping, brushingor spraying.

Inspection of the part is accomplished byviewing the part for color-contrasting indi-cations against the background surface if avisible dye penetrant is used, or by viewingthe part under “black” or ultraviolet lightin a darkened area, if a fluorescent dyepcnetrant is used. When using ‘(black”light, the inspector should become accus-tomed to the darkened area before lookingfor indications and should avoid going fromdark to light and back without allowingtime for his eyes to become dark-adapted,Sometimes an inspector experiences acloudiness of vision; this is caused by theliquid in the eyeball fluorescing under the

“black” light. It is annoying, but harmless.

PORTABILITY. Dve Denetrant ins~ec-. .tion facilities are available in portable Klt form foron-the-spot or field inspection in both visible andfluorescent dye types.

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I CLEANED .SURFACE PE/VETRAN 7 APPLIED

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FIGURE 71. Liquid penetmnl flaw deledwn.

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120 AGO 10117.4


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FIGURE74. Prod magnziization.

6.3 MAGNETIC PARTICLE TESTING. Mag-netic Particle Testing is used extensively for thedetection of surface dkcontinuities of ferro-magneticmaterials and, under certain conditions, those whichlie under but close to the surface.

6.3.1 BASIC PRINCIPLE. The process is bawdupon the difference in the ability to conduct magneticlines of force (magnetic permeability), between asound piece of steel and one with a discontinuity.When magnetic lines of force are present in aferm-magnetic material, any cracks, flaws, or otherareas of low permeability cet up a resistance to theirpassage. ‘l’he force lines spread out in order todetour this area. Immediately after passing thisarea, the distorted lines of force tend to recume theirnormal flow. when this low. permeability area is onor near the surface and the flux density is sufficient,many of the distorted lines of force will leave thematerial and enter the ,surrounding atmosphere in

MIL-HDBK-204

order to “bridge” the area. Where these force linesleave and re-enter the material, external magnetic

poles are produced on the surface which will attract

and hold finely powdered magnetic particles. Theparticles will generally conform to the shape of the

[email protected], thereby creating a visible indication,A crack at right angles t? the lines of force, interruptsthe most force lines, giving an indication of maximumiize. “’

6.3.2 MA GNETIZA TZON. Electric currentsare used to induce magnetic fields in the material.

The method of application of these currents willdetermine the direction of the lines of force so thatthey are at right angles to the anticipated discon.tinuities, Current passing through an objectlongitudinally will create circular lines of force,revealing any longitudinal cracks, when an objectis placed in a current-carrying coil, longitudinal linesof force are created, revealing any transverse cracks,Alternating or direct curr~nt may be used in thesetests. See figure 72.

6.3.3 METHOD OF APPLICATION. Thereare two methods of applying the magnetic pati]clesto a properly magnetized part, a “wet” and a “dry”method. In the wet method, the particles aresuspended in a liquid such as kerosene or a light clearoil, and flowed or sprayed on the surface to beinspected. In this method, the partkles are incontact with the entire surface of the part and it isrecommended only for machined surfaces. In the“dry” method, the partkdes are applied by spraybulb or shaker into the still air adjacent to the partand allowing them to settle evenly on the surface,This method may be uced on machined and ~B-machined surfaces. Particles for both the “wet” arid“dry” method are available in black or red for goodcolor contrast with the part being inspected. Theyare also available as fluorescent particles for viewingunder a “Black” or ultraviolet light for maximumvisibility. The “wet” fluorescent particle method isgenerally the faster and more sensitive ‘method.

6.3.4 CONTINUOUS AND RESIDUALMETHOD. When the particles are applied to thepart while the magnetizing current is flowing, thetechnique. is known as the “continuous” method,when the residual field left in the part is high, suchas in hardened steel parts, the particles may be

applied aftir the current has stopped. This is knownas the ‘(residual” method and is not as cencitive asthe “continuous” method.

MM 10117A 121

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---- -7.-

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6.3.5 PORTABILITY,’ Nfagnetic particle test:ing units are available in portable kit form forin-ssrvice or field testing in both visible and fluores-cent types with a variety of magnetizing sources suchm prods, cables, yokes, etc. See figures 73 and 74.

6.4 PENETRATING RAD1ATION TESTS.The ability of x-rays and gamma rays to perietrktesolid substances’and convey information ”concerningtheir internal structure is utilized in non-destructivetesting of materials.

6.4.1 FILM RADIOGRAPHY. Film’ radiog-raphy is a process in which the passage of x-raysorgamma rays through a test object’ produces aphotographic record on film.

6.4.1.1 Basic Principle. The rays emanate instraight lines from the source, which ‘may be anx-ray tube or a radioactive isotope, to the test object,The test object will absorb some of these raysandtransmit some. The amount of absorption foiagiven material is dependent upon the type of materialand its thickness in the dkection of travel of the rays,andcan be precisely calculated.

6.4.1.2 Film Interpretation. For example, if theobject is a steel casting having a void formed by agas bubble, a higher percentage of rays will passthrough the section containing the void.’ The voidrepresents a reduction in the total thickness of thesteel to be penetrated; therefore, a dark spot cor-

responding to the projected area of the void will

appear on the developed film, resulting in a kind ofshadow picture. The darker regions on the filmrepresent the more penetrable parts of the castingand the Iighter regions the more opaque. See figure75.

6.4.1.3 Advantages. Film radiography providesapermanent visible record of a metal product, thuspermitting its soundness to be further evaluated.

6.4.1.4 Por&zfJiMv. Radiograpbii units are’avail-able as permanent installatiims in a .skop or asportable tank units for field work.

6.4.1.5 Penebwneters, Asanaidin evaluating thesensitivity of the radiographic picture, it is cust-omary to place a’ standard test’ piece, called apenetrameter, onthesou;ie side of the test object,The usiml penetrarneter consists of a plaque of metal,radiographlcally similar to the”test object, havingholes and a thickness some percentage of the testobject (usually 2~o). Sensitivity is ‘determiried bythevisibility of the penetrameter on the finishedradiograph.

6.4.2 FLUOROSCOPE. Fluoroscope is the pro-

cess of examining an object by direct observationof the fluorescence of a screen caused by radiationtransmitted through the object.

6.4.2.1 Comparison wilh Film Radiography. Thebasic difference between fluoroscope and radiographyis that afluoroscopic image is a positive picture on a

screen and the radiograph is a negative transparency.The voids in the material under observation appearas lighter areas on the fluoroscopic screen, The

additional quantities of x-rays passing through avoid will activate the fluorescent crystals of thescreen toahigher degree of brightness.

mmFIGUEE 75. Film radiography—ptintiple ofoperalion,

6.4.2.2 Position of Test Object. The most directimage is obtained when the test object is placed inthe x-ray beam between the source and the back sideof the fluorescent screen. Theimage appears on thefront side of the screen.

6.4.2.3 Barriers. A transparent barrier, opaqueto x-rays, is placedin front of the screen to protectthe observer. The image is viewed through thistransparent barrier, thus permitting observationsatclose range. Thkisonly oneof several arrangementsavailable.

6.4.2.4 lfotion Obwwation. One of the greatestadvantages of fluoroscope is the fact that it permitsviewing of objects in motion. This allows theobservation of the action of switches, the arming offuzes, etc.

6.4.2.5 Installation. Fluoroscopic installationsare generally fixed-type installations because of theneed for a darkened area to view the screen.

6.4.3 RADIOISOTOPES. Gamma rays, emit-ted from a radioactive source such as radium, can beutilized as a means of measuring the wail thicknessof piping, vessels, etc. For the purposes of thisdiscussion on non-destructive testing, wall thicknessmeasurements shall be restrained to those measure-

122 AGO 1011TA


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MIL-HDBK-204

ments wh]ch are taken jn an effort to discover unsafeconditions in equipment where the interior is inac-ce~ible.

6.4.3.1 Basic Principle. A radioactive source isplaced in the vicinity of the part whose wall thicknessis to be measured. Penetrating gamma rays, emerg-ing from this source, impinge on the wall and

penetrate into it, A portion of the rays pass throughthe wall; these are disregarded. Another portion isscattered in all directions by the electrons of theatoms which make up the wall, Some of thesescattered rays emerge on the same side from whichthey entered. It is this portion of the radiation,called “back-scattering”, which is utilized for mem-uring wall thickness.

6.4.3.2 Detection. The “back-mattered” raJ,a-tion is picked up by means of a detector and sets offcurrent discharges or puhws which are amplified andregistered on a microammeter. The rate at whichthese pulses are generated is proportional to theintensity of the radiation entering the detector,which in turn is a function of the wall thickness.For a wall of any given composition, the intensity ofthe back-scattered radiation increases as a directfunction of the wall thickness,; therefore, the read,ngsobtained on the microammeter are directly indicativeof the wall thickness and may be graduated in inchesafter calibrating on specimens of tubing and plateshaving known wail thicknesses.

6.5 ULTRASONICS6.5.1 GENERAL, Sound waves, above and

beyond those which we hear, are utilized for thedetection of internal flaws in a large variety ofmetals. W]th ultrasonic inspection it is possible, tofind flaws in metal parts which cannot be detected byother non-destructive means and to determine theactual flaw geometry, size, and position.

6.5.1.1 Rejection. A characteristic of ultrasonicsound vibrations is their ability to be directed in abeam through an object and upon striking the oppos-ing outer wall, are bounced or reflected back as alight beam is reflected from a mirror, This charac-teristic is known as reflection.

6.5.1.2 Attermatiom. A second characteristic ofsound is its decrease of vibrational intensity ae itpassss through a conducting medium., The differencein the amount of energy conveyed into the body at

one surface and the amount received from it at the

OPPO.9ingSUrftWe is the quantity of sound energyabsorbed by the body, This decreasing or fallingaw~y of energy is known as attenuation,

FIOUBE76. Slmighl bmm march tmii.

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I+%z@5DAGO 10117A 123


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MIL-HDBK-204

6.5.1.3 fla~ottics. A third characteristic ofsound, in addition to the “Basic Period”, (and undercertain conditions) is the occurrence of harmonics,existing as multiples or sub-niultiples of the original

period which causes the part to vibrate.6.5.2 SEA RCH UNITS. Sound vibrations are

transmitted into a body by a transducer housed in asuitable holder (search unit), A transducer is aquartz crystal that has “the unique faculty of trans-forming Klgh-frequency, alternating ctiment intohigh-frequency, mechanical vibrations, This phe-nomenon is reversible since a varying mechanicalpressure will generate a pulsating current who&frequency is directly related to the rate of vibrationof the transducer, There are three general types of

search units that are employed in the majority offlaw detection.

6.5.2.1 Straight Beam Search Units. This type ofsearch unit projects a beam of ultrasonic vibrationsperpendicular to the test surface. It can be used foreither the reflection” (par, 6,5. 1.1) or the throughtransmission (par. 6,5.5) technique. f% figure 76.

6.5.2.2 Angle Beam Search Unit, This unit isused for testing plate and sheet material, pipe, andfor locating flaws which, due to their orientation,canuot be located by the straight beam method.The crystal is mounted on a plastic wedge so thatthe ultrasonic beam will enter the test material at aspecific angle. Sec figure 77(a), (b), and (c).

6.5.2.2 Surface Wave Search Unit. Surface wavesare used to scan the surface and a thin layer immedi-

ately below the surface. The’ crystal is momttidsimilar to the angle beam unit in that it uses ‘aplastic wedge but the wedge angle is such that theultrasonic beam is refracted at a 90” angle, F@re78 shows the wave traveling on the surface to ,adefect, where it is then reflected back to the searchunit.

6.5.3 CONTACT PULSE REFLECTION,Contact Pulse Reflection utilizes the first charac-

teristic of sound; reflection, The transducer, indirect contact with the test object through a couplingmsdium (thin coat of light oil), directs a pulsingtdtrasonic beam from 25 kllocyclesto 10 megacycleipcr second into the object. Tiieae transmittedpukes are timed w that the crystal is’ energized foranextremely short period, theresulting small groupsof waves being sent out at regularinterwds. Thecrystal is at rest for a ‘cornpara~ively long timebetween pukes, during which time the crystal acts asa receiver for the reflected wave trains from the

?ppOslte face or a defect or flaw in between. Thesereflected waves are then converted into an electricalimpulse by the reverse effect of the crystal, The

electrical impulse is fed into an amplifier and thenceto the plates of a cathode-ray oscilloscope. A linerepresenting the travel of the waves is transposed onthescreen of theoecilloscope. When a defector flawis present, the wave is reflected from the flaw andkomwquently returns in a shorter time causing ahump or variation in the tube trace, A distancemarker in the form of square waveacan reimposedon the screen, permitting the inspector to note thedepth of the defect. Theinspector merely moves the

crystal over the surface of the test object and watchesthe oscilloscope for any indications. See figure 79.

6.5.4 IMMERSION PULSE, REFLECTION,This process differs from the contact method in thatthe test object and the w.arch unit are immersedina tank containing water or other suitable liquidcouplant. The crystal is affixed to the end of ascanning tube that is attached to a movable carriage.The carriage has a longitudinal and transverse move-ment to permit complete scanning of the test object

and may be motorized o? manual. This methodenjoys certain advantages over the contact methodii that objects of irregular shape may be thoroughlytested. See figure 80.

6.5.4.1 Coupling, The surfaces do not requireany preparation as is sometimes necessary in contacttesting toinsure good coupling. Another advantageis, that due to the lack of intimate contact betweenthe test object and crystal, the problem of crystalwear” is removed. A thinner crystal may be em-ployed, ‘permitting higher frequencies (up to 25megacycles per second) which will pick up flawsmuch closer to the surface than the lower frequencies,

6.5.5 THROUGH TRANSMISSION, In theThrough” Transmission method of ultrasonic testing,as shown in figure 81, two transducers are employed,one to transmit and the other to act as a receiver.The process utilizes the second characteristic ofsound, that of attenuation. The immersion tech-nique may Au be employed in the Through Trans-mission method.

6.5.5.1 Flctw Detection, Acontinuous, rather thanpulsed, ultrasonic beam is ssit through the testobject by one transducer and is picked up by thereceiving transducer as a constant signal registration,except when a flaw is ericountered. The energypicked up by the receiving transducer is amplified

124 AOO10117A


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I AGO10117A

MIL-HDBK-204

sufficiently” to operate a trigger relay’ tied into any-ofssveral indicating, recording, or rejecting devices.

6.5.5.2 Disaduantagis. The Through Transmi~sion process is not in widespread use, the big dis-advantage being that access to both sidei,of the testobject ie required.

6.5.6 RESONANCE, Ultrasonic Reeonance

testing utilizes the. th]rd characteristic of” sound,resonant frequency and’ harmonics. Continuous,compressional, ultrasonic waves are transmitted bya transducer in direct contact (through a couplingmedium) with one face of a test object. The fre-quency (and therefore the wavelength) .of thesewaves are varied manually or automatically by anoscillator to bring the output to the correct fr~quencyto cause t.hepart t~vibrate in resonance. Atthis frequency, the particles of the material vibrateat their natural period or a harmonic of it andconsiderably more energy is required than normal tomaintain this resonant state of vibration. Because.of this characteristic when the resonant period isreached, the output meter shows a marked’changeinthe power required, This point isvery sharp and

if the oscillator is detuned ae little as lVO theindicated amplitude isgreatlyreduced. See figure82for idealized example of resonance.

6.5.6.1 Flaw Detectiw w’th Oscilloscope, In somesystems, a cathode-ray oscilloscope has been in-

corporated. The oscillating circuit contains a motordriven capacitor which is synchronized with tbehorizonth lsweepo fthetrac eacrossth ecathode-ray ,,tube. Each rotation of the capacitor produces avaring frequency range which is represented on thecathode-ray tube as the horizontal axis. If thisfrequency range contains resonant frequencies, thetrace line will be deflected vertically, producing mindication to the inspector.

6.5.6.2 Coupling. While thetransducer and part

can be immerssd, the transducer must always berelatively close to the surface of the test object. Itis not practical to couple the energy through a longliquid column, since theinstmments would de~ctand indicate resonant frequencies for the liquidcolumn,

6.5.6.3 F’ortabil;@. “Ultrasonic resorance equip-ment is widely used for non-destructive thicknessgaging of in-ssrvice equipment subject to corrosion.and for the detection of Iaminar dkcontinuitiee.Inherent accuracy, small size, and battery operationhave made this equipment particularly suitable forfield inspection.

125


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6.6 ELECTRO-MAGNETIC TESTS.

6.6.1 DIRECT CURRENT CONDUCTION.There m-e two techniques that employ the passage ofa direct current through the test object:

a. The direct current test method can be used forwall thickness ineasurements from one side only, butits greatest field of application is for depth measure-ment of cricks that are previously delineated byvisual observation, magnetic particle, or dye pene-trant techniques, In this ‘process, ”four phted,spring-loaded, hardened steel electrodes mounted inan’insulating head, are placed in contact titb i’

metal object to be tested. If an electric current, upto 10amperei, iscaused to flow between two of theelectrodes, apotential (volts) will reproduced in theother two electrodes. Inafixed electrode arrange-ment and with like materials, a change in ‘theresistivity of the material (such as that cauied by acrack or variation in wall thickness) will cause achange in the proportions of current and potentialand will be ‘registered on a moving coil. galvanometers,thess proportions having previously been setup .by ,acalibration specimen. The surface of the test object

needs only adequate preparation to insure goodelectrical contact,

b. In the other method, a heavy current of lowvoltage is passed through an object to be tested.This sets up magnetic lines of force that are perpen-dicular toandconcentric with thet.est object. Anydefect or flaw in the test object will reduce thecros~sectional area by an amount that is equal to thetransverse area of that defect. The current flowwill be deflected by the flaw, thereby causing a

proportionate deflection of the magnetic lines offorce; see figures 83, and. 84. If a coil is movedthrough this magnetic field at a constant speed,parallel to the axis of the test object, a voltage will beinduced in tbe coil where it cuts a decreasing numberof lines of force, This will occur at the depressedmagnetic field surrounding the defect, Thk voltagemay be noted on a meter or it may be amplified toactuate a marking mechanism.

6.6.2 EDDY CURRENTS. Inan eddy current(orelectro-magnetic induction) test, the metal testobject is inserted in the varying magnetic field of acoil, carry ingan alternating current. Thetest objectconstitutes the core of this coil and is the recipient ofeddy currents induced by the AC magnetic field ofthe coil. The.w eddy currents, in turn, produce anadditional AC magnetic field in the vicinity of thetest object, which is superimposed on the originalmagnetic field of the coil, causing a variation ormod]tication of the original magnetic field of the coil.

6.6.2.1 Now Indications. Tbe coil is part of atuned circuit and these variations produce powerlosses in the circuit which are measurable and areused in various ways to give indkations on a cathode-ray tube. Indications areobtained without electricalcontact inassbort atimeas l./1000sscond, therebypermitting the establishment of high speed, auto-matic inspection procedures. Eddy current methodsof non-destructive testing are among the fastest testsavailable.

6.6.2.2 Coil Shapes. Coilshapes include: Solenoidor feed-through coils, inside coils, hand-probe coils,fork-shaped coils, and specially shaped coils forspecific test objects.

6.6.2.3 Appli&&ions. Eddycurrent tests maybeused on a variety of ferrous and non-ferrous parts ofmany forms. It is one of the most versatile of thenon-destmctive tests. Some of the physical prop-erties tested by this method include: Electricalconductivity, Cracks, Hardness, Depth of case,Plating thickness, Diameter, etc.

126 AGO 10111A

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.6.2.4 The coil method is only one of severalvariations of eddy current, testing, many dbTerenttype instruments being available for whatever typeof test desired.

AGO IOI17A


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MIL-HDBK-204

INDEX

(Numbers shown in this Index refer to p.ragrapb8.No page references are givem)

.A

Accuracy, Degree of, 1.8.1.1Acme threads, 4.3.2Active Coils (l>ef.),2,3.10.3Actual Space Width (Def.), 4.4,2,7Actual Tooth Thickne.s8 (Def. ), 4.4.2.8 ,,Adjustable Gage (Def,), 1.2.3.10Adjusting Devices, 2.3.3: - .,fmcmomandSpecialM echaniBme,2 .3.3.2 “Screws, 2.3.3.1

Air PremureIndicators; 3.12.2,2 .,AlignmentCoOimstmC06ineation, 5:7.1.2.3Description, 5.7.1.2.1OpereAiOn,5.7.l.2.2 . ,., .

“Alignment T8rget,5.7.l.5.l , ,, : ,Alignnient”TelemmpeDewmiption 5.7.1.1.1 ...Magnifying Power and Range, 5,7.1.l.2 ~

Alloying Elements, Effects of, in steel, 2.4.2Alloy Tool Steel, 2.4,5Allowable ErmrE (Def.), 4,4,2,5Allowable Errors for Spline Gages, 4.4.9.2Allowance (Def.), 1,2.2.6Alumin”rn a“d Magmsium, Use of, 2.4,11American Gage Deaig” Standard (Def.), 1.2.3.9Analysk of Inspection RequirementsAnalysi80f Prod”ct Drawing8, 1.7.4 ,1,7,4.1Anal~8ia of Quafity AByran~e’Pmvision8,1 .7.5, 1.7.5.1B~ic Catigoriesof I@ection, 1.7,2Detarminstim of In.specticm Equipment Requirements,1,7,6

Object of Inspection, 1.7.1Respon8ibiiitiea of Inspection Engineer, 1.7.3,1.7.3.1,1.7.3.2

Annealing and St- Relieving, 2.4.1.4@pfic8tiomof the A“t.c-f%llimatorAngle Comparison, 5.6.6.1Axial Squareness, 5.6.6,8Checking with s Sine Bar, 5.6.6,4Direct Angle Check, 5.6.6.2Indirect Angle Check, 5.6,6,3Impectio”of Optics, 5.6.7Parallelism, 5,6.7Straightness or Flstnew Check, 5.6.6.6The Optical Lever, 5.6.6.5

Atte”tuation, 6.5.1.2AutiCcdfimation, Description of Pmcees, 5,7,2.2.2Autc-fkdlimation, Gemm.1 Explmation of, 5.6.2Autm-(%llimstim Unit, 5,7.2.2Au&CollimatorAdvantages of Parallel Light, 5.6.4.2Construction of, 5.6.3l)etermimtionof Accuracy, 5,6,4.1FKt”re Type, 5.6.5.4Micrometer Eyepiece, 5,6.5.1

Microscope Eyepiece, 5.6.5.2Off-Axis Pinhole Tvm, 5.6.5,3

~ Refinements of D;[gn’,5 .6.5Theory of, 5.6.4

Auto-Reflection, I)e,criptionof Process, 5.7.2.2.1Auto-Reflection Target, 5.7.1 .5.1Axle Mirror, 5.7,2.7.1

B

Backing-flp Method, Locating by, 2.3.2.5Bmei Gage-( Oef. ), 1.2.3.4Baaic Size (f)ef .), 1.2.2.5Bilateral Tolera”ce(De f,), 1.2.2 .7.2Black Oxide F!nish, 2.5.2Blank, Gage (Def.), 1.2.3.5Brass, Bron%e,and Copper, U8e of, 2.4.12BuilbUp SnapsAlignnxat of A“vila, 3.4.2.3.1,Gcmer81Constructio” Feature~, :1.4.2.1Idmtificatirm of Go a“d Not Go Ends, 3.4.2 .1.2Receaa?SdAnvH~, 3.4.2.3Relieved Awils, 3.4.2.4

; Sep.arate Receiver, 3.4.2,2Type. of>3,4.2 .1.1Use of Check Gages, 3.4.2.2.1

Balls Eye Led, 5.7,2 ,5.1

cCaliper Gage (Def.), 3.1.9Caliper Gage, Uesign Comideratiom, 3.8.1Carbon Steel, 2.4.5Case Harde”i”g, 2.4,1,6Cat Iron, Use of, 2.4.7Cast Steel, Use of, 2.4.6Chip Grooves, 4.2.2.1.2Chrome Plating, 2.5.1Clarity, JnsF.tion %uipment Drawi”@EnlargedSections, 1.5.4 .1.1Minor Clearances, 1.5.4 .1.2

Clwificatio. of Drs.wiwgsCataloging, 1.5.3 .1.1Specisl Drawings, 1.5.3.2Standard Drawinga, 1.5.3.1.2Standards, 1.5.3.1

Clearance (Def.), 1.2.2.8Coi”cidemxLevel, 5.7.2 .5.3Collimation, General Explanation of, 5.6.1Collineation, 5.7.1.2.3Cornparstor Gage (Def.), 3.1.10Comparator Gage, Construction, 3.!1.1Component (Oef.), 1.2.1.3Construction Practice8, GeneralAdjusting Devices, 2.3,3Castings Vs. Machimd Part.v, 2.3.8Commercial Parts, 2.3.6

128 AGO 10117.4


MIL-HDBK-204

Fabrication,23.1Helical Cornpremion and Extension Springs, 2.3.10Idercbfmgeable and Replaceable Elements, 2.3.4IOcaticm, 2.3,2Q uic kOpemting Devices, 2.3.9Standard Partior Mechanisms, 2,3,5Univereal TYLMEquipment, 2.3,7

ControlSize (D”ef.), 1.2.2.3Convoluting(BkmtMart), 4.2.2.1.1Cyli”dricd Plug Gsges,Plai”

Go PlwgB,3.2.1.1.1Minor Dkmeter Plugs,3.2.1.1.3Not Go PIwI, 3.2.1,1,2Sourcee. of, ii,l.1

D“

Deflection (Uef.),2.3.10.5 ‘VeeiK” of Impecti.n EquipmentFor Experimental Items, 1,7,6,3.1For Standardized Items, 1.7.6 .3,2

Deaign Size (Def.), 1.2.2.4Detailkem.bly Drawing, Selection of, 1.5.2 .3.2Determining Proper Measuring Pin8 for Splinea, 4.4.10.1Dinll”dicatora, MechanimlAGD Speci6cation8, 3.12.2.1.5Graduation, 3.12.2 .1,2Indicator Gwwds.3,12.2.l.4Bang., 3.12.2.1.1’Type of Mounting, 3.12.2 .1.3

DimensionalChromePlating, 2.5.1Dimemionirw md TolersncirmApplicationof Dimemim8and Tolermces, 1.5.4.2,2,3llet.il l)irnemiona,1.5.4.2,2UimemimingS@em, 1.5,4,2.2.2GagitlgDirnenaionB,1.5.4,2,1Pwitional Tcderances, 1.5,4 ,2,2.1

Vi8placement Target% 5.7.1.5.2Vouble Line Target.v,5.:.l.5.5Dowels, Locating by, 2.3.2.1Drawing Practiww, Impxticm EquipmentAbbreviation, 1,5.4.5Chritv. 1.5.4.1 ,’Cr0e8”Reference, 1.5.4.7

I Delirmaticmof Commercial Iterm. 1.5.4.3.Dimemio”ing a”d Toleranci”g, 1:5.4.2Drawing Symbols; 1,5.4.9Dm.wi”g Titles, 1’.5,4.8Identification lbta, 1.5.4.6Refereme Dimemions, 1.5.4.2,3Replaceable and Interchangeable Elements, 2.3.4:3scale, 1,5.4.4Standard Parts or Mechtmimm, 2.3,5.1

Drawings, Inspection’ Equipment, Type8 ofDetAiled Drawings, 1.5.1.1Specifice.tion Type, 1.5,1.2

I>ri]l Rod, 2.4.5 ‘,

E

Economyof Des@, 1.8.1.3Eddy CurrmtTesting

Applications,6,6.2.3 ,,

Aoo i0117A

Coil Shapes, 6.6.2.2Flaw I“dicatiom, 6,6,2.1

Effective Clearance (Def.), 4.4.2.3Effective Error (Def,), 4.4.2.5.5Effective Fk (Def.), 4.4.2.4Effective Space Width (Def. ),4.4.2.lEffective Tooth Thickness (Def.), 4,4,2.2ElettmMagnetic TestingDirect Current Co”ductio”, 6.6,1Eddy Current, 6.6.2

E“d Item (Def.), 1.2.1.4E“gi”eeri”g Ccurdimtirm, Splines, 4.4.4.3Engineering Orders, 1.6Edsrged Swtiom, 1.5.4.1.1Error Allowance (Def.), 4,4.2.6Experimental Items, Inspection Equipment for, 1.7.6.3.1External Fkmb Pin, 3.6.4

FFabrication, Inspection EquipmentBy Brazing, Soldering, etc., 2.3.1.3By Screws, 2.3.1.1By Welding, 2.3.1,2Integral Part Vs. Fe.bricsted Part, 2.3,1.4

Fibn RadiographyAdvmtages, 6.4.1.3B~ic Pri”cipie, 6.4.1.1.Fihn Interpretation, 6.4.1.2Penetrametem, 6.4.1.5Portability, 6.4.1.4

FimdInspectionGage8,Govemment(D ef.), 1.2:3.1Fit. (Def.), 1.2.2.10Fixed Gage (Def.), 1.2.3.11Fixture Gage (Def.), 3.1.12Fixture GageaEconomy in Manufacture, 3.11.2 thru 3.11.2.4General Construction, 3.11.1Operating Mecbani.vrm, 3.11.3Part Location, 3.11.1.2Replacement Elemmts, 3.11.4Uwof Maters, 3.11.1.1Welded Construction, 3.11.1.3

Flat Cylindrical Plug, Applications, 3.2.2.1Depth Checking Steps, 3.2.2.2

Fluom.wopyBarriers> 6.4.2.3Comparison witb Film Rndiograpby, 6.4.2.lInstallation, 6.4.2.5Motion Observation, 6.4.2.4lbition of Test Object, 6.4.2,2

Fkmh Pin Gage (Def.), 3.1,7Flush pin Gaee8Applications, 3.6.1Barrel Type, 3.6.2.1Bar Type, 3.6.2.2Built-Up Type, 3.6,9,Carbide Inserta, 3.6.4.2.1.External Type, 3.6.4For Depth of Drilled Holes, 3.6.4.2For Ueptb of Thread Cavity, 3.6.4.1Gemml Construction Feature% 3.6.2

129


MIL-HDBK-204

Genera}DesignCriteria, 3.6.3lnternd Type, 3.6.5MultipleType, 3.6.8, 3.6.S 1,3.6.8.2Spring Loaded Type, 3.6.7Taper Type, 3,6.6

Frame, Gage (Def.), 1.2.3,6Free Length (fief.), 2.3.10,10Full Annealing, 2.4.1.4Functiomd Gage (f)ef.), 1,2,3,13

GGage (D~f.), 1,2,1,7Gage Nome.clatw?, 3.1.2G%. NOmencMure, lnvOl.te Splin- and Serrations, 4.4.5External, 4.4.7Internal, 4.4.6

Gage Specification, 1,5,5,1Gage Titles, Sample, 3.1,13Gage Tolerance (Def.), 1.2,2 .7.3Gage Tolerancing Policy, 2.2.3Gaging Aids (Def.), 1.2,3,3General Construction, Fixtme Gages, 3.11.1General Construction, Receiver Gages, 3.10.3General Laws of Geometrical Optics, 5.1.2General Laws of Light, 5.1.1Go Gage (Def.), 1,2.3,12,1

HHandle, Gage (Def.), 1.2,3.7Hardermbility, Steel, 2.4.1.3Hardening and Qwmches, 2.4.1,5Harmonica, 6.5.1,3Heat Treatment (Def.), 2.4,1.1Heat Treatment, Theory of, 2.4,1.2Helical (lmnpr=irm and Extemion Spti”g~, ‘2.3.10Horizrmtnl Toofing Bar, 5.7.1 .6.1

IIdentification f)ata, Thread GagesNonstandard Threads, 4,2,5.3Not Go Gage, NS Thread, 4.2.5.2Standard Threads, 4.2.5. i

Immersion Puke Be flectio”, 6,5,4Coupling, 6.5.4.1

Implied Geometric Requiremmtq 2,2.7Index to Inspection Equipmmt ListiAuxiliary Uses, 1.4.4.4Excessive “NL’s”, 1.4.4 .2.1“L” (bef.), 1.4.4.1“NL” (Def.), 1.~.4.2Numbering, 1.4.4.? ,,,

Inapctio” Equipnxmt LbJtsCamponition of an l,EL Package, 1.4.1Index, 1,4.4List of Inspection Equipment, 1.4.5List of Inspection EquipmeM Numbers, 1.4,6f%paration of the J.kta, 1.4.2Principal Index, 1.4.3Revision of Li.9tn, 1.4.7

Intqwxtirm Equipment, Whmffequiw.i, 1.7.6.1Not Required, 1.7.6.2

Instrument Stands, 5.7.1 .6.3I“terchrmgeable Element, 2.3.4.1I“terferometryAbmlute M.wferometry, 5.9.4.2Determim.tion of Flatnw, 5.9.3Interpretation of Interference Bfmds, 5.9.2Productim of Interference Bands, 5.9.1Meaauremmt of Height, 5.9,4Measurement of Height by comparison, 5.0.4.1

involute Spline8 and SerrationsCompleti P,oduct Specifications, 4.4.3flefinitim of Terms, 4.4.2Gage Blsnk8, 4.4.SGages for External Sp]ims, 4,4.7Ge.gea for Idernal Splines, 4.4.6Gaging, 4.4.1Incompletely Dlmemioned Prcduct8, 4.4.4Macbinimg Tolerance .md allowable errors for Gages, 4.4.9Measming Pi”s, 4,4.10Nmnencltttwe, 4.4.5

JJig Transit, 5.7.1.3.1Justification of Extent of In8pecti0n Equipment Design,1.7.6.3

KKcywayn, Imnting by, 2.3.2.4

LLight, General Nature of, 5.1.1Limit Gages (Def.), 1.2.3.12Limi@ (Def.), 1.2.2.9Liquid Penetmnt TestingBaaic Process, 6.2.1Portability, 6.2.3Variations, 6.2.2

Lint of Inspection Equipment NumbersThe Basic List, 1.4,6,1The Croes Refermce List, 1.4,6,2

List of Inspection EquipmentAesembly a“d Sub-Aenembly Lists, 1,4.5.2Multiple Applicaticm, 1.4.5.3Numbering, 1.4.5.1Revie.irm of, 1.4.7.1

f,osd (Def,), 2.3.10.4Load-fleflection Tsblw, AccurscY of, 2.3.10.2Load-DeSmtion Tabka, Use of, Page 4SIacstmm and Speci.1 Mecbani8ms, 2.3:3.2

M

Machining Tolerance (Def.), 4.4.2 ,6.1Machining Tolerance for Spline Gages, 4.4.9.1Magnet Back Mirror, 5.7.2 .7.2Msgmtic Particle Teati”gBasic Principle, 6.3.1Continuous and Rtidual Methcd, 6:3.4Magnetization, 6.3.2Method of Application, 6:3.3Portability, 6,3.5

Manufacturing Gagea (Def.), 1.2.3.2

130 AGO 10117A


~. ,. .. . . . . . .. , ,. . .

MIL-HDBK-204

Master(lkf.), 1,2.3,14 Generalf)esignFeature8,5.8,5,1MaaterChwk Gage (fief.), 1.2.3,14.2 GeneralFestures,5.8.4.1MasterGage (Def.), 1.2,3 .14.1 Indirect Observation, 5.8.5.3MaEters, Scttiug, 3.12.3 TyP@ cd, 5.8.4.2Mtiterials; Selecticm, Hezt Treatment, and Applicntio” T.yues of Stnginu Fixtures, 5.8.5,2Annealing and Stress Helievi”g, 2.4,1.4Brass, Bronze, and Copper, 2.4,1.2Ce.aeHardening, 2.4,1.6Cast Iron, 2.4,7Cast Steel, 2.4,6Effects of Alloying Elementi, 2.4.2General, 2,4.1Hardenability, 2.4.1.3Hardening and Quenches, 2,4.1.5Heat Treatment (Def.),2.4.l.lMachine Steel, 2.4,4Magnesiwn .md A1.minum, 2,4,11Phwtica, 2.4.13Sapphire, 2,4.10Semi-Steel, 2.4.8Si”temd Carbides, 2,4,9Stabilization, 2.4,3Tempering, 2.4,1.7Tbeuryof Heat Treatment, 2.4.1,2Tool Steel, 2.4.5

Maxinmm Gage (Def.), 1,2.3,12.3Me.usmringEquipment (Def.),1.2.l.9Member, Gage (Def.),1.2.3.8Microscope, Types of, 5,4.1Minimmn Gage (Def.), 1.2.3 .12.4Mirror Targeia, 5,7,1 .5,4Mono-Detail Drawing, Selectimof, 1.5.2 ,3.1Multi-Element Plug GageaApplications, 3.2.6.1Dwig” Comidemtions, 3,2.6.2, 3.2.6 ,2,1

Multiple Threads, Gwes forIdmtificstion Data, 4.2.6 .4,4,2.6.5Dwign C!cwaiderationa,4,2.6.1Not Go Gages, 4.2.6.3Thread Stmfa, 4.2.6.2

NNominal Ciears”w,4 .4.2.9 ‘NmnimJSize(Def,), 1.2.2.2Normalizing, 2,4.1.4Not Go Gage (Def.), 1,2.3 .12.2 . .

Adjustable Plugs, 3.2.30 Cylindrical Step Plugs, 3.2.1,2.2

Object oflnspectirm, 1,7.1 Flat Cylindrical ,Plu@, 3,2.2Operating Mechanisms, for Fixture Gagea, 3.113 Flat Pk@, 3.2.5optical Projection Functional Plugs, 3.2,1.2.4General Requirermmta for, 5,8.2 Multi-Element Pl”gx,3,2.6optical Projectom, 5.8,4 Pilot Plugs, 3.2.1.2.1Principle of, 5.8.1 Phi” Cylindrical Plugs, 3.2,1Requimmtm~ for Obtilni”g Maximum Image Sharpuws, Recessd Type PhIgs, 3.2.1.2.35.s.3. Special Cylindrical Plugs, 3.2.1.2

Screen Charta,5.8.7 Taper Plugs, 3.2.4Specific Design 1mtmctionn,5 .8.6 Practicnlityof Design, [email protected] Fixtures, 6.S,5. PreparatiOIIof ImpectimIEq”iprnent Dmwinge

Optical Projectors Detail Ae.sembly,.l ,5,2.2Auxifimy Gaging, 5.8.5.4 Mont-Defail, 1.5.2.1Design Imtnmtions, 5.S.6 Selection of, 1,5.2.3

Opt~c~l Micmm-eti~,5 .7.2.1OpticalSquare, 5.7.2,6Optical ToolingAccewm-ka, 5.7.2Alignment Calfime.tor, 5.7.1.2Alignment Telescope, 5.7.1.1Jig Tramit a“d Optical Transit Square, 5.7.1.3kvefs, 5.7.2.5Mirrors, 5.7,2.7Targets, 5.7.1.5Tilting Level, 5.7. I.4Tooling Ban? and Instrument Stinds, 5.7.1.6

Tooling Tapes, 5.7.2.8Typ OfEquipment, 5.7.1

Optical Tramit Sqware, 5.7.1 ,3,2Optics, Geometrical, General Lmvsof ,5.1.2O“tif-Romd”m (Def,), 4,4.2.5,4

P

Parallelism Error (Def.), 4,4.2.5.3Part (Def.), 1.2.1.2Penetrating Radiatirm Teati”gFilm Radiography, 6.4.1F]”or0w3py, 6,4.2H8diosotopf?s, 6.4.3

Piece (Def.), 1.2.1.1Pipe Threads, 4.3.1Gaging NFTF Pipe Threads, 4,3, I. 1,2.1NPT 4,3.1.1,1NP’YF 4.3.1.1.2Taper 4.3.1,1

Pitth, Spring (f)ef.), 2.3.10.13Plain Ring GageaGo Rings, 3.3.1.1.1Not Go Ri”gs, 3.3.1 .1.2B0urces0f,3.3.l.1

Phstim, Use of, 2,4.,13Plug Gage (Def.),3.L3 ,Pluc Gaeea ‘

AGO 101I7A 131


-— .——.. . ; , —.—.— —

MIL-HDBK-204

Principal Index of Inspection Equipment ListsNumbering, 1.4.3.2Resuomibilitv. 1.4.3.1

Pmbi~gMediums,Non-llwtructive Testing,6.1.1Product (I)ef.), 1.2.1,5ProfileError (Def.), 4.4.2.5.2Pmtilea, Templafe Gages forAcceptance Check, 3.5.3,2, 3.5.3.3Application, 3.5.3. IGeneral Talerancing of, 3.5.3 ,1,1

Projection Eyepiwe, 5,7.2.3Projection of MaterialsChromium Plate, 2:5.1Protective Finishes, 2.5.2

P“blimtiomMil-Standards, 1.5.6.2Specifications, 1.5.6.1Other Publications, 1.5,6.3

Q

,

Quality .kssurrmw’Quality Requireme~ta Engineering,’ 1.3.3.]Inspection Equipment Engineering, 1.3.3.2Impection Equipment Supply, 1,3.3.3Q.dity Sysfem Evaluation, 1.3.3.4

QualityAmmmce Provisions, Analynis of, 1.7.5, 1,7.5i”Quick Operating Devices, 2.3.9

RRadioieotope8Basic Principle, 6.4.3,1f)etiction, 6.4.3.2

Receiver Gage (Def.), 3.1.11Receiver Gag=Applications, 3.10.1Check Gages, 3.10.4, 3.10.4 .1,3.10.4.2Deaig” Cansidemtionn, 3,10.2General Construction, 3.10.3

Recessed Plug Gage, 3.2.1.2.3Reference flimenaions, 1.6.4.2.3Reflection, Ultr-nit, 6.5.1.1Replaceable Element, 2.3.4.2Replacement Elements for Fixture GaRea, 3.11.4

,’

,,, ,

~uirementa, Impscti.n Equipment,Ddiermin.ationof; 1.7.6ReSOnaWeTesting ~ .: ~~ ,,,,.,..

Coupling,&5.6.2Flaw,DetectionwithGacilloscope,6.5,6,1 ,,,Portability,6.5.6.3 !:

Responsibilities,InspectionEquipmentE.sinear, 1.7.3Revisions

Drawings,1.5,9 ,,Lists,1,4,7

Right AngleEyepiece, 5.7.2.4Ring Gage (Def.), 3.1.4 . .Ring GabPlain Rings, 3.3:1Plain Sfep Rings, 3.3.1,2,1Special Rings, 3.3.1.2Taper Rings, 3.3.2

Roll Thrend Plug, Bar TypeAccuracy, 4.2.2.7.2Applicatkm, 4.2.2 ,7.1

Roll Thread SnapAccwacy, 4,2,3 .9.2Applic.aticm, 4,2.3 .9,1Supplementary Gaging, 4.2.3.0.3

sSalvage Plating, 2.5.1Sapphire, Use of, 2.4.10Screen CbarbAccuracy, 5.8.7.3General Feature%,5.8.7.1Methods of Screen Layout and checking, 5.8.7.4Overscreen Chart, 5.8.7 .2.1Types of Screem, 5,8.7.2

Search UnitsAnule Beam Unit, 6.5.2.2Str;igbt Beam unit, 6.5.2.1‘Surface W.ve Unit, 6.5.2.3

Segment Type Thread PlugsApplication, 4.2.2 .6.1Cost Comideration, 4,2.2.6.3Setting and Acceptance Plugs, 4.2.2 .6.2

Selection of Inspection EquipmentDegree of Accuracy, 1.8.1.1Economy, 1.8.1.3Practicality, 1.8.1.2Required Attribute%, 1.8.1Semi-BWI, UseJof, 2.4.8Setting Masters, 3.12.3

Sintered Carbide, Use of, 2.4.9Snag Gage (Def.), 3.1.5snap G&i”Adjustable Snap, Bbide TYpe Anvils, 3.4.1.2Adjustable Snap, Modified Anvils, 3.4,1,1Builbup Smps, 3.4.2Carbide Imerta, Use of, 3.4.2.5Plain AdjuMable Snaps, 3.4.1Plate Gages, SnaP Type, 3.4.3Recessed Anvil Type, 3.4.2,3Relieved Anvils, 3.4.2.4Separate Receiver Type, 3.4.2.2

Soft Plugs, Use of, 2,3.2.2Solid Length (Def.), 2.3.10.12Sp.ce, Spring (Def.), 2.3.10.6Spanner Gage (Def.), 3.1.8Spanner GagesBasic Cmstmction, 3.7.4, 3.7.4.1, 3.7.4.2General Design Data, 3.7.1Multiple Pi” (Hole) Gagen, 3.7.3, 3.7.3.1TWOPi” (Hole) Gagea, 3.7.2

Specific Gmmetric Requirement, 2.2.’6Spheroidizing, 2.4.1.4Splims and Sermtiom, ExtermdComplef@ Product Specifications for, 4.4.3.2Gages for, 4.4.7Go Com~site Rin&, 4.4.7.1Setting Mmtem for Go and Not Go Snapn, 4.4.7.4

132 AGO10117.4


,, ,, + ,7 .—_.. a ..

I

Snap Gag-, 4.4.7.3T.pered Tooth Maahm, 4,4.7.2

Splin~ and &rratiom, Internalcomplete Product Specification for, 4.4.3.1Gages For, 4.4.6Go Compaeiti Plug, 4.4.6.1Go Paddle Plug, 4.4.6.2Not Go Paddle Plug, 4.4.6;3

Spring Index (Def.), 2.3.10.11Stabilization of Steel, 2,4.3Staging FixturesAuxiliary Gaging, 5.s.5.4Compenmti.g Type, 5.S.5.2.1Deeign Instmctiorm, 5.8.6General Design Features, 5,8.5.1Indirect Observation, 5.8.5.3Permanent Aligned Type, 5.S.5,2.2Position Locking Type, 5.S.5,2.3

Standardizxtio. of Thread Gages, 4.2.1.1Stmdard Size (Def.), 1.2.2.1Steel, Machi”g, I)ascription a“d uses of, 2.4.4Sub-Critical Anmdi”g, 2.4.1.4Symbols, Impectim E.q”ipmmt Drwvi”gHardness Symbols, 1.5.4.9. ISurface Fi”isb, 1.5,4.9.2Tolerance, 1.5.4.9.3Welding, 1.5.4.9.4

T

Taper Pins, Locating by, 2.3,2.3Taper Plugs, Use of, 3.2.4.1Dimensioning of, 3.2,4.2General Design of, 3.2.4.3

Taper Rings, Uae of, 3,3.2.2Dimensioning of, 3.3.2.3General Deaig” of, 3.3.2.4, 3.&2.5

Technic.1 Data PackageContent of tbs Qutiity Aammnce Area, 1:3:3Tbe Product Area, 1.3.1Tbe Quslity Asmramx Arm, 1,3.2

TelescopesBasic Optical Cbamcteri8tim of, 5,5.1Construction, 5.5.2Field of View, 5.5. I.4Lena System, 5.5.2.1Magnifying Power, 5.5.1.1Range, 5.5,1.2The Eye Piece Momti.g, 6.5.2.3The Mmmt, 5.5.2.2

Tempering Steel, 2.4.1.7Tc!mplate Gages (Def.), 3.1.6Template GagesApplication, 3.5.3,1Gages for Depth and L.engtha, 3.5.2Gages for Profiles, 3.5.3General Conatruetio”, 3.5.1Uee of Scribed Limes, 3.5.2.1

TerminologyDimcmiond, 1,2.2

Gage, 1.2.3General, 1.2.1

Test Equipnxmt (Def.), 1.2.1,8Thread Gages, ExternalGo Thread Ring, 4.2.3 .1,4,3.3,1.1Lengtk Requirement, 4.2.3.7, 4.2.3.7.1, 4.2.3.7.2, 4.2.3 .7.3Major Diamekr Adjwtable Smp, 4,2.3.6, 4.2.3.6.1Not Go Thread Ring, 4.2.3,2Roll Thread Snap, 4.2.3.9Segment Type Thread Fhg, 4.2.3,S, 4.2.3.S,1Tbrmd Setting PIuK, 4.2.3.4, 4.2,3.4,1TYPU, 4.2.3.3”

Thread Ga.es. r“temal. .Depth Requirement, 4.2.2.4, 4,2.2.4,1, 4.2.2.4.2, 4.2.2 ,4.3Go Thread Plugs, 4.2.2,1Handles, 4,2,2.5Minor Diameter Plugq 4.2,2.3Not Go Taperlock Blank, 4.2,2.5.2Not Go Thread Plugs, 4.2,2.2No Go Trilmk Blank, 4.2,2 .5.1Roll Tbrmd Plug, Bar Type, 4.2.2.7Segment TSW Thread Plum, 4.2.2.6-.

Through Tre.mmiesicm TestingDisadvantages, 6.5.5.2Flaw lletectirm, 6.5.5,1

Tilting Level, the, 5.7,1,4Tolerance (Def.), 1.2.2.7Tolerances and AllowancmGage Tolerancing Policy, 2.2.3General, 2.2. IImplied Geometric Req”irementa, 2.2,7Specific Geometric Req”iremmts, 2,2,6Surface Fi”iab, 2.2.8Tolerame8 for “After Psinti&’ Gages, 2.2.4.2Tolerances for Gaging Dimensiom, 2.2.4Tolersmea for Gemerd (Xmstrwtim IT,membm, 2,2.2Tolerrmcw for Maximum or Mi”imwn Gag=, 2.2.4.1Wear Allcnwmce, 2.2.5

Tolersmes md Allowsmm Thread Gsg~Claeaificatio”, 4.2.4.6Distributirm, 4.2.4.5Flank Angle Tolerances, 4.2.4.4Gages, 4.2,4,1Lead Toleramw, 4,2,4.3Standard Toler!m.ea, 4.2.4.2

Tool Steel, Description a“d Uwa of, 2.4.5Tooling TapesApplication of Temperature Correction, 5.7.2.8.3Temperature Correction, 5.7.2.8.2.Tension Certificate, 5,7.2 .8.1

Total Index Error (Def.), 4.4.2,5,1Total Tolerance (Def.), 4,4.2.6.2Tubular Level, 5.7.2.5.2Two l% (Hole) GageDiameter of Holes (Female GaEe), 3.7.23Diameter of Fins (Male Gage), 3.7.2.2Distance between Ce.tem, 3.7.2.1Implied Dirnwmiona, 3.7.2.5Ucation from 8 Surface, 3.7.2.4

AGO 10L17A


—- ..—..—;— — .- .— ., —.— —

MII.-HDBK-2O4

uUltrasonics

ContactPulse Reflection, 6,5.3 ,,.Gemml, 6.5.1Immersion Pulse Reflection, 6.5.4.Resonance, 6.5.0Search Units, 6.5.2Through Transmimioq 6.5.5

Lhilied a“d America” Natiom+l Thread, Standardization.4.2,1,1

Unilateral Toler8.ce (Dcf. ), 1.2.2.7,1Universal Equipment, 2.3.7

.,

.

v

Vertical Tooling Bar, 5.?. 1.6.2

w

Wear Allowance, 2.2.6Wear Limit Gage (Def.), 1.2.3.15Wear Surface Plating, 2.5.1Welding Symbols, 1.5.4.9.4Wire Diameter, Specifying, 2.3. 10.!)

,. ...:

134 AGO 1011TA


,.—, ,—,, —. —,. ~~.-. — ~ . *-

,,.“INSTRUCTIONS: lp.a r.ontinuiugeffort b make our standardization documentsbet~, the DoD prcmides~i[oti for w in*bndt&tg commenk and @gestions ior improvements. AN uaemof military staadudimtion .docnuterdsare httited to ptotidamqestiom. l%h form IMY be detached, folded along the Iinea indicatcidfi taped along tbe loom edge (DO NOT ST_#Y,BJ, mnd

mtiled. h! block 5, he u specific M Poaoible about particular problem &w such u utwding which m.qulred iet+6tetb~ wtoo rigid, mStriCtkVeti@aCI, ambiguous, or w incompatible,andgivePropmed wording chqm which wtdd @!?vlstd tbaprobleias. Enter in b&k 6 any remarks not related to a specific pamgmpb of the document. If block 7 is filhd 6UG anacknowledgementwill be tied to you within 80 days to let you know that your commenb worn rm?chd and are belaEconddemd.

NOTE: Tbii form & not be wed to tiqueat copies of documentq nor to request waivem, dtitioas, or cldk~n ofspecification kquim&Its on current contracts. Comments mbmittedon tbi# form do not cmutthtte or Inmlv mtbtittohh ,miw any portion of the referenced document(,) or to amend contractti rqdremenu.

. .

I

(Fold .dc.rwthtiIlru)

DEPARTMENT OF THE ARMY

OFFICIALEUStNE~PENALtV FOR ●RtVAIE USE urn

111111FIUNITED STATES

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BRl#NE~SNR~2WYMAILWASHINGTON 0. C.

AFf2STAGE WILL BE PAID BY THE DEPARTMENT OF THE ARMY

Commander !

US Army Armement Research and Development Command ~ATTN: DIU)AR-TST-S

~Dover, NJ 07801

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STANDARDIZATION OOCUMENT IMPROVEMENT PROPOSAL,. (See Instructions -R fvertiSide)

1. DOCUMENT N>M9ER ‘2. DOCUMENT TITLE

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Ea NAME O$SU6MI’WINGOISGANIZAIION 4, TYPE OF ORGANIZATION (Mai+ mu).. . ‘; ❑ VENOOR

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