TM 9-243
TYPES AND USES
Ring and snap gages and precision gage blocks are
used as standards to determine whether or not one or
more dimensions of a manufactured post are within
specified limits. 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 the use.
RING GAGES
SNAP GAGE NONADJUSTABLE
The following classes of gages and their limits of
accuracy are standard for all makes: Class X Precision
lapped to close tolerances for many types of masters
and the highest quality working and inspection gages.
Class Y Good lapped finish to slightly increased
tolerances for inspection and working gages.
Class Z Commercial finish (ground and polished, but not
fully lapped) for a large percentage of working gages in
which tolerances are fairly wide, and where production
quantities are not so large.
Class ZZ (Ring gages only). Ground only to meet the
demand for an inexpensive gage, where quantities are
small and tolerances liberal.
SNAP GAGE - ADJUSTABLE
GAGE BLOCKS
The table below lists the tolerances for ring gages in
each class:
RING
TO AND
GAGES
ABOVE INCL
X
Y
Z
ZZ
0.029
0.825
0.00004
0.00007
0.00010
0.00020
0.825
1.510
0.00006
0.00009
0.00012
0.00024
1.510
2.510
0.00008
0.00012
0.00016
0.00032
2.510
4.510
0.00010
0.00015
0.00020
0.00040
4.510
6.510
0.00013
0.00019
0.00025
0.00050
6.510
9.010
0.00016
0.00024
0.00032
0.00064
9.010
12.010
0.00020
0.00030
0.00040
0.00080
X
Precision lapped
Y
Lapped
Z
Ground or polished (grinding marks may be in evidence)
ZZ
Ground only
15-2
