GAUGES

GAUGESGauges perform an essential services in any scheme of quantity production on an interchangeable basisA gauge (or Limit Gauge) is a tool or instrument to measure or compare a component.It is employed in the sense of an instrument which having fixed dimension, is used to determine whether the size of some component exceeds or is less than the size of the gauge itself 28/01/2012lec# 7 & 81

GAUGES (cont..)Gauges are used for dimensional control of the component parts , their function being to establish whether or not surface levels lie within the zone specified by the designer.Gauges must be manufactured & checked with reference to standard of length, which in turn is related to a fundamental length standard. The standard of length is then transferred through the gauge to the component28/01/2012lec# 7 & 82

GAUGES (cont..)The true value of a gauge is measured by its accuracy & service life which, in turn, depends on the workmanship & materials used in its manufacture. Since all gauges are continually subject to abrasive wear while in use, the selection of the proper material is of great importanceHigh carbon steel & alloy tool steels have been the principal materials for manufacture of such gauges 28/01/2012lec# 7 & 83

THE TAYLOR PRINCIPLETaylors Principle lays it down: A GO Gauge will check all the dimensions of the work piece in what is called the maximum metal condition (indicating the presence of the greatest amount of material permitted at a prescribed surface) That NOT GO Gauges shall check only one dimension of the work piece at a time, for the minimum metal conditions (indicating the presence of the least amount of material permitted at a prescribed surface) size 28/01/2012lec# 7 & 84

THE TAYLOR PRINCIPLE (Cont..)In case of hole, the maximum metal condition obtains when the hole is machined to the low limit of size, & minimum metal condition results when the hole is made to the high limit of size. in case of shaft the limits taken would be inverse of hole28/01/2012lec# 7 & 85

Classification of Limit Gauges Production gauges are of various types, but there is a little doubt that the majority are in the form of limit gauges.These are designed to cover a very wide range of work.The general form of limit gauges is of the fixed type. That is to say, gauging contact elements remain fixed during the gauging process. Gauging elements, however, may be provided with means for size adjustment 28/01/2012lec# 7 & 86

Classification of Limit Gauges (cont..)Following gauges are the most commonly used in production work. The classification is principally according to the shape or purpose for which each is used. Snap gauges5. Form Comparison Gauge Plug gauges6. Thickness Gauges Ring gauges7. Indicating Gauges Length gauge8. Pneumatic Gauges28/01/2012lec# 7 & 87

Classification of Limit Gauges (cont..)Electric Gauges Electronic Gauges Projecting Gauges Multiple Dimension Gauges

28/01/2012lec# 7 & 88

Description of some commonly used gauges:Snap Gauges: A Snap gauge is used in the measurement of external dimensions, It consist of a U-shaped frame having jaws equipped with suitable gauging surfaces. A plan gauge has two parallel jaws or anvils which are made to some standard size & cannot be adjusted They may be either single-or double -ended28/01/2012lec# 7 & 89

Description of some commonly used gauges: (Cont..)Snap Gauges: (Cont..)e.Special forgings & stampings are available commercially for their manufacture, or they may be constructed from gauge platef. Special snap or gap gauges may have to be used for checking the recessed diameters & other features 28/01/2012lec# 7 & 810

Snap Or Gap Gauge

28/01/2012lec# 7 & 811

Description of some commonly used gauges: (Cont..)Plug Gauges: A plain plug gauge is an accurate cylinder used as an internal gauge for size control of holes It is provided with a suitable handle for holding & is made in a variety of stylesThese gauges may be either single or double endedDouble ended plain gauges have GO and NOT GO members assembled on opposite ends, where as Progressive gauges have both gauging sections combined on one side

28/01/2012lec# 7 & 812

Description of some commonly used gauges: (Cont..)Plug Gauges: (cont..)Possible Forms of Plug Gauges:Solid Type (Double ended) Solid Type (Single ended) Renewable-end type (Double ended) Progressive Type Shell form type (Double ended) Shell form type (Single ended) Bar end Type Special Types28/01/2012lec# 7 & 813

Plug Gauge

28/01/2012lec# 7 & 814

Description of some commonly used gauges: (Cont..)3. Ring Gauges: Used to gauge outside diameters Used in Pairs as Go & Not Go4. Taper Gauges:Taper gauges are not dimensional gauges but rather a means of checking in terms of degreesTheir use is a matter more of fitting rather than measuring

28/01/2012lec# 7 & 815

Ring, Taper Plug & Taper Hole Gauge

28/01/2012lec# 7 & 816

Description of some commonly used gauges: (Cont..)5. Thickness or Feeder Gauge:It consist of a number of thin blades & is used in checking clearances & for gauging in narrow places6. Dial Gauge:Dial gauges or Dial Test Indicators are used for checking flatness of surfaces & parallelism of bars & rodsThey are also used for testing the m/c toolsThey can also be used for measurement of linear dimensions of jobs which require easy readability & moderate precision

28/01/2012lec# 7 & 817

Thickness Gauge

28/01/2012lec# 7 & 818

Dial Gauge

28/01/2012lec# 7 & 819