Classification Of Gauges Used In Metrology | Types Of Gauges

INTRODUCTION TO GAUGES
Gauging, done in manufacturing processes, refers to the method by which it is determined quickly whether or not the dimensions of the checking parts in production, are within their specified limits. It is done with the help of some tools called gauges. A gauge does not reveal the actual size of dimension.
A clear distinction between measuring instruments and gauges is not always observed. Some tools that are called gauges are used largely for measuring or layout work. Even some are used principally for gauging give definite measurement.
classification of gauges in metrology
classification of gauges in metrology
High carbon and alloy steels have been the principal material used for many years. Objections to steel gauges are that they are subjected to some distortion because of the heat-treating operations and that their surface hardness is limited. These objections are largely overcome by the use of chrome plating or cemented carbides as the surface material. Some gauges are made entirely of cemented carbides or they have cemented carbides inserted at certain wear points.

GAUGES AND THEIR CLASSIFICATIONS

Gauges are the tools which are used for checking the size, shape and relative positions of various parts but not provided with graduated adjustable members. Gauges are, therefore, understood to be single-size fixed-type measuring tools.

Classifications of Gauges

(a) Based on the standard and limit
(i) Standard gauges
(ii) Limit gauges or “go” and “not go” gauges
(b) Based on the consistency in manufacturing and inspection
(i) Working gauges
(ii) Inspection gauges
(iii) Reference or master gauges
(c) Depending on the elements to be checked
(i) Gauges for checking holes
(ii) Gauges for checking shafts
(iii) Gauges for checking tapers
(iv) Gauges for checking threads
(v) Gauges for checking forms
(d) According to the shape or purpose for which each is used
(i) Plug
(ii) Ring
(iii) Snap
(iv) Taper
(v) Thread
(vi) Form
(vii) Thickness
(viii) Indicating
(ix) Air-operated
Standard Gauges
Standard gauges are made to the nominal size of the part to be tested and have the measuring member equal in size to the mean permissible dimension of the part to be checked. A standard gauge should mate with some snugness.
Limit Gauges
These are also called „go‟ and „no go‟ gauges. These are made to the limit sizes of the work to be measured. One of the sides or ends of the gauge is made to correspond to maximum and the other end to the minimum permissible size. The function of limit gauges is to determine whether the actual dimensions of the work are within or outside the specified limits. A limit gauge may be either double end or progressive. A double end gauge has the „go‟ member at one end and „no go‟ member at the other end. The „go‟ member must pass into or over an acceptable piece but the „no go‟ member should not. The progressive gauge has „no go‟ members next to each other and is applied to a workpiece with one movement. Some gauges are fixed for only one set of limits and are said to be solid gauges. Others are adjustable for various ranges.
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