Machining Fundamentals
68
4.4.2 Ring Gage
External diameters are checked with ring gages.
The go and no-go ring gages are separate units, and
can be distinguished from each other by a groove
cut on the knurled outer surface of the no-go gage.
Refer to Figure 4-30.
On ring gages, the gage tolerance is the reverse
of plug gages. The opening of the go gage is larger
than the opening for the no-go gage.
Figure 4-29. A step plug gage can check for oversize and
undersize in a single test.
Figure 4-28. A double end cylindrical plug gage.
Figure 4-30. Ring gages. The larger sizes are cut away to
reduce weight. (Standard Tool Co.)
4.4.3 Snap Gage
A snap gage serves the same purpose as a ring
gage. Snap gages are designed to check internal
diameters, external diameters, or both. There are
three general types:
• An adjustable snap gage can be adjusted
through a range of sizes. See Figure 4-31.
• A nonadjustable snap gage is made for one
specific size. See Figure 4-32.
Figure 4-31. An adjustable snap gage. (Taft-Pierce Co.)
Gage size
For
checking
O.D.
For
checking
I.D.
Figure 4-32. Diagram of a nonadjustable snap gage. A—A com-
bination internal-external nonadjustable snap gage. B—An
external nonadjustable snap gage.