TM 1-1500-204-23-9
(b)
Second type. Another type is
made in sizes that range from 1/2 to 11-1/4 inches. It is
equipped with four gauging buttons and is suitable for
checking flat or cylindrical work. This type is shown in
figure 3-63.
(c)
Third type. The third type is
made in sizes from 1/2 to 11-5/8 inches. Shown in
figure 3-64, it is equipped with two gauging buttons and
a single block anvil, and is especially suitable for
checking the diameters of shafts, pins, studs, and hubs.
b.
Tolerances. Depending on the use, snap
gauges are manufactured to different tolerances. The
following classes of gauges 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
gauges.
Class Y
Good
lapped
finish
to
slightly
increased tolerances.
Class Z
Commercial finish (ground and
polished, but not fully lapped) with
fairly wide tolerances.
Tolerances for snap gauges in each class are listed in
table 3-2.
c.
Using an Adjustable Snap Gauge. The
following paragraphs describe the procedures for setting
the snap gauge, and measuring flat and cylindrical
parts.
(1)
Setting the snap gauge. Before an
adjustable snap gauge can be used to check parts, the
GO and NO GO buttons, pins, or anvils must be set to
the proper dimensions.
Figure 3-61. Progressive Snap Gauge
Figure 3-63. Snap Gauge for Checking Flat or
Cylindrical Work
Figure 3-62. Snap Gauge for Checking Dimension
Between Surfaces
Figure 3-64. Snap Gauge for Checking
Diameters
3-29
