PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2
(11) Ring and Plug Gages.
(a) General. Ring, plug, snap, and precision gage blocks are used
as standards to determine whether or not one or more dimension is within
Their measurements are included in the construction of
each gage, and they are called fixed gages. However, some snap gages are
adjustable. Gages are used for a wide range of work, from rough machining
to the finest tool and die making. The accuracy required of the same type
of gage will be different, depending on their use.
(b) Ring Gages.
1 A ring gage (figure 27 on the following page) is a
cylindrical-shaped disk that has a precisely ground bore.
Ring gages are
used to check machined diameters by sliding the gage over the surface.
Straight, tapered, and threaded diameters can he checked by using the
The ring gage is also used to set other measuring
instruments to the basic dimension that is required for their particular
operation. Normally, ring gages are available with a GO and a NO GO size
that represents the tolerance allowed for that particular size or job.
2 The plain gage is an external gage of the circular form.
For sizes between 0.059 and 0.510 inch, ring gages are made with a hardened
steel bushing and pressed into a soft metal body. The thickness of the gage
will range from 3/16 to 1 5/16 inches. On ring gages, the GO gage (1) is
larger than the NO GO gage (2).
The GO and the NO GO ring gages are
They can be distinguished from each other by an annular
groove (3) cut in the knurled outer surface of the NO GO gage. Ring gages
made for diameters of 0.510 to 1.510 inches are the same as those in figure
27, except that there is no bushing; they are made all in one piece. Ring
gages, sized from 1.510 to 5.510 inches are made with a flange (4). This
design reduces the weight, making the larger sizes easier to handle.
3 Ring gages are used more often in the inspection of
finished parts than of parts in process. The reason for this is that the
finished parts are usually readily accessible; whereas parts in a machine
that are supported at both ends would have to be removed to be checked.