Page 110 - CITS - Fitter - Trade Theory

FITTER - CITS

Centre gauge: -

A centre gauge is made up of spring steel hardened and tempered and is used mainly for grinding and setting
single point thread cutting tool. These gauges have graduation for checking the number of threads per inch. Some
gauges have a table giving the double depth of various threads and also used to check the included angle 60° of
ground lathe centres.

The notches on the edge of the gauge are for checking the correct width of point of the tool according to the
number of threads per inch specified for acme thread. It is made of spring steel and hardened. Similarly, a metric
thread gauge is also available.

Standard Wire Gauge (SWG): -
It is used to measure the size of a wire and thickness of sheet shown in. The standard wire gauge is a circular
metal disc with varying hole and slot size on its circumference. Each slot size corresponds to a gauge number
which is written just below the hole. The gauge numbers specify the size of a round wire in terms of its diameter.As
the gauge number increase from 0 to 36, the dia size decrease. The thickness of sheet metal and the diameter of
wires confirm to various gauging num bers and the following Table 1 give the decimal equivalents of the different
gauge numbers for the diameter of wires, and the thickness of sheets

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CITS : CG & M - Fitter - Lesson 15 CITS : CG & M - Fitter - Lesson 15