Plain Plug Gauge
Plug gauge is used for the assessment of the hole or diameter of an object. With specified tolerance of GO and NOGO side, plug gauge is also known as pin gauge.
Behalf of checking the diameter plug gauge also use in comparing, setting, calibrating of other gauges.
Plug gauges are available in a variety of tolerance of Metric or British standard.
As shown in the figure. let say plug gauge size is 25H7 where H7 stand for tolerance standard(+0.0/+0.27)
so, GO side is 25.00 mm
and NOGO side is 25.270 mm
The easy way of finding GO/NOGO side
Go side of plug gauge is always less in diameter but larger in length. But in the case of NOGO, the diameter of NOGO is always greater than the GO side.
Easy measurement by plug gauge just assesses by which side of gauge fit in the hole.
Snap gauge is GO and NOGO type gauge. That means snap gauge consist of 2 fixed measured distance or gap, one is known as GO and another one is known as NOGO.
GO means your job or workpiece is OK and NOGO means your workpiece is rejected.
In snap gauge, the value of GO is always greater than NOGO.
Let set an example,
we have a snap gauge of size
12.500 +/_ 0.050 mm
GO size = 12.550 mm
NOGO size = 12.450 mm
and it is measuring criteria for a workpiece.
According to snap gauge, 25.55 mm size is acceptable for a workpiece. When we push snap gauge towards the workpiece the only area of GO cover i.e. workpiece is accurate.
If Snap gauge is able to move till the NOGO area that means the workpiece is undersized.
Snap gauge is usually checked for the outer surface, which can easily be observed favorable or not.