01.Limits Fits59.Edited

7/28/2019 01.Limits Fits59.Edited

1/24

FUNDAMENTALS OFLIMITS, FITS & TOLERANCES


2/24

2

Different types of tolerances are

Dimensional Tolerances

Form Tolerances

Position Tolerances

Surface Roughness values

Combination Tolerances

Other details shown on drawing are

Material specification

Special treatments if any

Heat treatments

Assembly condition

Special notes

Tolerance: Tolerance is the total permissible variation from the specified basic size ofthe part. It is defined as the magnitude of permissible variation of a

dimension or measured control criterion from specified value.

Basic size: The basic size is the size on which variation permitted.

Actual size: The size of a feature obtained by measurement


3/24

3

TOL not specified

Follow general engineering tolerance

IS 2102 fine, medium, coarse & very coarse

Unless otherwise specified, it is medium.

Or else it can be IT 14 VALUE, bilateral

All drawings need contain conditions on general tolerance.

Open tolerances or General Engineering tolerances Standards used areIS 2102 ( Part

1)

1993 / ISO 2768 - 1 : 1989

General Tolerances

Part 1: Tolerances for Linear and Angular dimensions without individual tolerance

indications

Part 2: Geometrical Tolerances for features without individual tolerance indications

Ex: 20.0, 20-f, 20-f H


4/24

4

Table 1 Permissible deviations for linear dimensions except for broken edges

(external radii and chamfer heights, see table 2)

Values in millimeters

Tolerance Class Permissible deviations for basic size range

Desig

nation

Descripti

on

0.5

up to

3

Over

3

up to

6

Over

6

up to

30

Over

30

up to

120

Over

120

up to

400

Over

400

up to

1000

Over

1000

up to

2000

Over

2000

up to

4000

f fine 0,05 0,05 0,1 0,15 0,2 0,3 0,5 -

m medium 0,1 0,1 0,2 0,3 0,5 0,8 1,2 2

c coarse 0,2 0,3 0,5 0,8 1,2 2 3 4

v very

coarse

- 0,5 1 1,5 2,5 4 6 8

For nominal sizes below 0,5 mm, the deviations shall be indicated adjacent to the relevant

nominal size (s).


5/24

5

Table 2 Permissible deviations for broken edges

( external radii and chamfer heights)


Designation Description 0.5 up to 3 over 3 up to6 over 6f fine

0,2 0,5 1m medium

c coarse 0,4 0,1 2

v very coarse

For nominal sizes below 0.5 mm, the deviations shall be indicated adjacent to the relevant

nominal size(s).

Table 3 Permissible deviations of angular dimensions

Permissible deviations for ranges of lengths, in millimeters,of the shorter side of the angle concerned

Designation Description up to 10 over 10 up to

50

over 50 up to

120

over 120 up

to 400

over 400

f fine 10 00 30 00 20 00 10 00 5

m medium

c coarse 10 30 10 0030 00 15 0010

v very coarse 30 20 10 0030 00 20

Tolerance class

Tolerance class Permissible deviations for basic size range


6/24

6

Table 1 General tolerances on straightness and flatness


ToleranceClass

Straightness and flatness tolerances for ranges of nominal lengths

up to 10over 10up to

30

over 30up to100

over100 upto 300

over 300up to1000

Over1000up to3000

H 0,02 0,05 0,1 0,2 0,3 0,4

K 0,05 0,1 0,2 0,4 0,6 0,8

L 0,1 0,2 0,4 0,8 1,2 1,6

Table-2 General tolerances on perpendicularity


ToleranceClass

Perpendicularity tolerances for ranges of nominal lengths of

the shorter side

up to 100over 100 up

to 300over 300

up to 1000over 1000up to 3000

H 0,2 0,3 0,4 0,5

K 0,4 0,6 0,8 1

L 0,6 1 1,5 2


7/24

7

Table-3 General tolerances on symmetry

Values in mm

ToleranceClass

Symmetry tolerances for ranges ofnominal lengths

up to 100over 100up to 300

over 300up to 1000

over 1000up to 3000

H 0,5

K 0,6 0,8 1

L 0,6 1 1,5 2

Table 4 General tolerances on circular run-out

Values in mm

Tolerance class Circular run-out tolerances

H 0,1

K 0,2

L 0,5


8/24

8

IS 2102 PART 2

VALUES FOR - Straightness / Perpendicularity / Symmetry / Runout specified

Circularity - Limited to diameter tolerance or runout value

Cylindricity - Limited to combined effect ofCIRCULARITY & PARALLELISM.

Parallelism - Limited to Dimensional Tolerance & flatness tolerance.

Coaxiality - Limited to runout tolerance.

ISO 2768 - m

General Engg. Tolerance class medium

IS 2102

f General Engg. Tolerance class fine

ISOmK

General Engg. Tolerance for dimensions - Tolerance class. m

General Engg. Tolerance for form / position Tolerance class. K

ISO 2768 - K

General tolerance as dim not considered.

Form/position as per tolerance Class K.


9/24

9

SPECIFIED TOLERANCE

VALUE GIVEN

VALUE AND POSITIONAL STATUS GIVEN

STD. SYMBOLS USEDSpecificied tolerances

Standards used

IS 919 (Part 1) 1993 / ISO 286 1 : 1988

ISO System of Limits and Fits

Part 1: Bases of tolerances, Deviations and Fits

Part 2: Tables of standard tolerance Grades and limit Deviations for Holes and shaft.

Example : 20H7, 20g6, 30 + 0.02

Specific tolerance should be less than open tolerance

STANDARD SPECIFICATIONNeed contain

HOW MUCH IS THE VALUE OF TOL.

WHERE IT IS DISPOSED.


10/24

10

HOW MUCH IS THE VALUE

IS 919 / SP46 OR STD CHARTS SPECIFY.

18 GRADES ARE SPECIFIED. VALUE IS ATTACHED TO A GRADE

IT=INTERNATIONAL TOLERANCE GRADE. AND 18 REPRESENT THE ROUGHFEST MANUFACTURING PROCESS.

EVERY MANUFACTURING PROCESS IS ATTRIBUTED WITH A RANGE OF ACCURACY GRADEHOWMUCH IS THE VALUE

FOR EX:

TURNING IT7, 8 OR 9

GRINDING IT 5, OR 7

MILLING IT 6, 7, OR 8

LAPPING IT 1, 2, 3, OR 4

SAND CASTING IT 16, 17, 18

PRESS WORKING IT 10, 11 OR 12

INJ. MOULDING IT 12. 13 OR 14

Grades of tolerances obtainable by various manufacturing processes

According to IS 18 grades of tolerances or accuracy grades of manufacturing IT1, IT2,

IT3.IT18

IT GRADE is generally indicated by numbers from 1 to 18


11/24

11

Manufacturing Processes IT grades

Lapping 1,2,3,4

Honing 3-5

Laser beam machining 5,6,7

Super finishing 4-6

Grinding 4-8

Electric Discharge machining 6-7

Boring 5-9

Reaming 5-8

Broaching 5-9

Turning (Diamond tools) 4-7

Turning 7-12

Milling 8-10

Shaping 10-14


12/24

12

Drilling 11 14

Extrusion 9 12

Blanking 12 18

Drawing 10 14

Die Casting 12 15

Sand casting 14 16


EVERY DIM. ALONG WITH A GRADE RECEIVE A TOL. VALUE.

FOR EX. DIM. 40 & GRADE 8, TOL= ?

STD. FORMULA APPLIES TO THIS VALUE

FOR CONVENIENCE, DIMES. ARE GROUPED. 0 TO 3; 3 TO 6; 6 TO 10 etc.

SAME VALUE OF TOL. VALID FOR A DIA GROUP WITH ONE GRADE.

Manufacturing process IT grades


13/24

13

Table 1Numerical values of standard tolerance grades IT for basic sizes up to 3150 mm

Standard tolerance gradesBasic size

mm IT12) IT22) IT32) IT42) IT52) IT6 IT7 IT8 IT9 IT10 IT11 IT12 IT13 IT143) IT153) IT163) IT173) IT183)

Above

Up to

and

includ

ing

Tolerance in microns Tolerance in mm

- 33 0,8 1,2 2 3 4 6 10 14 25 40 60 0,1 0,14 0,25 0,4 0,6 1 1,4

3 6 1 1,5 2,5 4 5 8 12 18 30 48 75 0,12 0,18 0,3 0,48 0,75 1,2 1,8

6 10 1 1,5 2,5 4 6 9 15 22 36 58 90 0,15 0,22 0,36 0,58 0,9 1,5 2,2

10 18 1,2 2 3 5 8 11 18 27 43 70 110 0,18 0,27 0,43 0,7 1,1 1,8 2,7

18 30 1,5 2,5 4 6 9 13 21 33 52 84 130 0,21 0,33 0,52 0,84 1,3 2,1 3,3

30 50 1,5 2,5 4 7 11 16 25 39 62 100 160 0,25 0,39 0,62 1 1,6 2,5 3,9

50 80 2 3 5 8 13 19 30 46 74 120 190 0,3 0,46 0,74 1,2 1,9 3 4,6

80 120 2,5 4 6 10 15 22 35 54 87 140 220 0,35 0,54 0,87 1,4 2,2 3,5 5,4

120 180 3,5 5 8 12 18 25 40 63 100 160 250 0,4 0,63 1 1,6 2,5 4 6,3

180 250 4,5 7 10 14 20 29 46 72 115 185 290 0,46 0,72 1,15 1,85 2,9 4,6 7,2

250 315 6 8 12 16 23 32 52 81 130 210 320 0,52 0,81 1,3 2,1 3,2 5,2 8,1

315 400 7 9 13 18 25 36 57 89 140 230 360 0,57 0,89 1,4 2,3 3,6 5,7 8,9

400 500 8 10 15 20 27 40 63 97 155 250 400 0,63 0,97 1,55 2,5 4 6,3 9,7

500 6302

9 11 16 22 32 44 70 110 175 180 440 0,7 1,1 1,75 2,8 4,4 7 11

630 8002

10 13 18 25 36 50 80 125 200 320 500 0,8 1,25 2 3,2 5 8 12,5

800 10002

11 15 21 28 40 56 90 140 230 360 560 0,9 1,4 2,3 3,6 5,6 9 14

1000 1250

2

13 18 24 33 47 66 105 165 260 420 660 1,05 1,65 2,6 4,2 6,6 10,5 16,51250 1600

215 21 29 39 55 78 125 195 310 500 780 1,25 1,95 3,1 5 7,8 12,5 19,5

1600 20002

18 25 35 46 65 92 150 230 370 600 920 1,5 2,3 3,7 6 9,2 15 23

2000 25002

22 30 41 55 78 110 175 280 440 700 1100 1,75 2,8 4,4 7 11 17,5 28

2500 31502

26 36 50 68 96 135 210 330 540 860 1350 2,1 3,3 5,4 8,6 13,5 21 33

1) Values for standard tolerance grades IT01 and IT0 for basic sizes less than or equal to 500 mm are given in ISO 286 1, annex A, table 5.

2) Values for standard tolerance grades IT1 to IT5 (incl.) for basic sizes over 500 mm are included for experimental use.

3) Standard tolerance grades IT14 to IT18 (incl.) shall not be used for basic sizes less than or equal to 1 mm.


14/24

14




Table 1-Numerical values of standard tolerance grades IT for basic sizes up to 3150 mm

Basic size

mm

Standard tolerance grades

IT1 2( IT2 2( IT3 2( IT4 2( IT5 2( IT6 IT7 IT8 IT9 IT10 IT11

Above Up to andincluding

Tolerances in microns

--- 33 0.8 1.2 2 3 4 6 10 14 25 40 60

3 6 1 1.5 2.5 4 5 8 12 18 30 48 75

6 10 1 1.5 2.5 4 6 9 15 22 36 58 90

10 18 1.2 2 3 5 8 11 18 27 43 70 110

18 30 1.5 2.5 4 6 9 13 21 33 52 84 130

30 50 1.5 2.5 4 7 11 16 25 39 62 100 160

50 80 2 3 5 8 13 19 30 46 74 120 190

80 120 2.5 4 6 10 15 22 35 54 87 140 220

120 180 3.5 5 8 12 18 25 40 63 100 160 250

180 250 4.5 7 10 14 20 29 46 72 115 185 290

250 315 6 8 12 16 23 32 52 81 130 210 320

315 400 7 9 13 18 25 36 57 89 140 230 360

400 500 8 10 15 20 27 40 63 97 155 250 400

500 630 9 11 16 22 32 44 70 110 175 180 440

630 800 10 13 18 25 36 50 80 125 200 320 500

800 1000 11 15 21 28 40 56 90 140 230 360 560

1000 1250 13 18 24 33 47 66 105 165 260 420 660

1250 1600 15 21 29 39 55 78 125 195 310 500 780

1600 2000 18 25 35 46 65 92 150 230 370 600 920

2000 2500 22 30 41 55 78 110 175 280 440 700 1100

2500 3150 26 36 50 68 96 135 210 330 540 860 1350


15/24

15

Table 1Numerical values of standard tolerance grades IT for basic sizes up to 3 150 mm

Standard tolerance gradesBasic size

mm IT12 IT13 IT143) IT153) IT163) IT173) IT183)

AboveUp to and

includingTolerances

mm

- 33

0,1 0,14 0,25 0,4 0,6 1 1,4

3 6 0,12 0,18 0,3 0,48 0,75 1,2 1,8

6 10 0,15 0,22 0,36 0,58 0,9 1,5 2,2

10 18 0,18 0,27 0,43 0,7 1,1 1,8 2,7

18 30 0,21 0,33 0,52 0,84 1,3 2,1 3,3

30 50 0,25 0,39 0,62 1 1,6 2,5 3,9

50 80 0,3 0,46 0,74 1,2 1,9 3 4,6

80 120 0,35 0,54 0,87 1,4 2,2 3,5 5,4

120 180 0,4 0,63 1 1,6 2,5 4 6,3

180 250 0,46 0,72 1,15 1,85 2,9 4,6 7,2

250 315 0,52 0,81 1,3 2,1 3,2 5,2 8,1

315 400 0,57 0,89 1,4 2,3 3,6 5,7 8,9

400 500 0,63 0,97 1,55 2,5 4 6,3 9,7

500 6302 0,7 1,1 1,75 2,8 4,4 7 11

630 8002 0,8 1,25 2 3,2 5 8 12,5

800 10002 0,9 1,4 2,3 3,6 5,6 9 14

1000 12502 1,05 1,65 2,6 4,2 6,6 10,5 16,5

1250 16002 1,25 1,95 3,1 5 7,8 12,5 19,5

1600 20002 1,5 2,3 3,7 6 9,2 15 23

2000 25002 1,75 2,8 4,4 7 11 17,5 28

2500 31502 2,1 3,3 5,4 8,6 13,5 21 33





16/24

16


60% INCREASE IN TOL. VALUE FOR EVERY GRADE UP FOR A DIAGROUP

EVERY 6TH GRADE GETS 100% MORE TOL VALUE

WHERE TO DISPOSE TOL.

TOL. CAN BE DISPOSED

ABOVE BASIC DIM.

BELOW BASIC DIM

DISTRIBUTED ON EITHER SIDE

WHERE TO POSITION

POSITIONING IS REPRESENTED BY CAPITAL LETTERS FOR HOLES A,B,H

BY SMALL LETTERS FOR SHAFTS a,b,h STD DISTANCES ARE KEPT EACH LETTER & FOR EACH DIA GROUP FROM BASIC

DIM.

THE DISTANCE TO THE BASIC DIM WITH LEAST VALUE IS TERMED ASFUNDEMENTAL DEVIATION

FUNDAMENTAL DEVIATION IS FIXED FOR A DIA-DIM COMBINATION.


17/24

17

Schematicrepresentation ofthe positions offundamentaldeviations


18/24

18


19/24

19

FITSWhen two parts to be assembled, the relation resulting from the difference between the

size before assembly is called a fit.

A fit is represented by 30 H 7 / g6, 30 H 7 / p6, 40 H7/h6, 40 H7/k6, 40 H7/p6,


20/24

20

Transition fit


21/24

21


22/24

22


23/24

23

Note: G Go , N No Go , Tolerances in microns 1 micron = 0.001 mm


24/24

24

MMC, LMC & RFS

MMC - Dimension corresponding to Maximum Material Condition

(Biggest shaft size or smallest hole size)

LMC - Dimension corresponding to Least Material Condition

(Smallest shaft or biggest hole size)

RFS - Regardless of feature size

Actual Dimension vary from MMC limit to LMC limit

Worst assembly condition exist when mating parts at MMC

Functional assembly requirements can be related to actual dimension by

symbol in the drawingM

Date post:	03-Apr-2018
Category:	Documents
Upload:	maddyscribd
View:	218 times
Download:	0 times

01.Limits Fits59.Edited

Documents