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70 Part II: Metrology
Ring gage accepting part that is out-of-round
Go gage
No-go gage
Step 1: Go gage slips over shaft
Step 2: No-go gage will not slip over shaft
Part II.A.2
Snap gage rejecting part that is out-of-round
Go
Step 1: Part enters go gage
and does not enter no-go
(q)
No-go
Step 2: Same part when inspected 90° from
first position will enter no-go gage
Figure 7.10
Continued.
by a threaded collet and bushing (view 1), a taper lock where gage members have
a taper shank on one end that fits into the end of the handle (view 2), or a trilock
where the gage members have a hole drilled through the center and are counterbored
on both ends to receive a standard socket-head screw (view 3). One way of
checking a hole for out-of-roundness is to have flats ground on the side of the gage
member, as shown in Figure 7.10c.
Ring Gages. Ring gages, such as those shown in Figure 7.10d, are used for checking
the limit sizes of a round shaft. They are generally used in pairs: the go gage
for checking the upper limit of the part tolerance and no-go gage for checking
the lower limit. The no-go ring has a groove in the outside diameter of the gage
to distinguish it from the go ring. It is possible that a shaft’s ends are larger than
the middle, or it could suffer an out-of-roundness condition. This situation can not
be detected with a standard cylindrical ring gage. Such an out-of- roundness
condition can be checked by a ring gage that has the inside diameter relieved,
such as the one shown in Figure 7.10e.
Snap Gages. A snap gage is another fixed gage with the gauging members specially
arranged for measuring diameters, thickness, and lengths. An adjustable