Use. The small hole gauge consists of a
small, split, ball-shaped member mounted on the end of a
handle. A hole smaller than 1/2 inch is measured by the
Insert the proper size gauge in the hole,
as shown in figure 3-80.
Expand the ball by turning the knurled
knob in the handle until there is a slight drag of the ball on
both sides of the hole.
Withdraw the gauge and measure the
ball with an outside micrometer.
Some types of small hole gauges have
flattened ball ends to permit use in shallow
holes and recesses.
Care. Observe the following practices for the
care and upkeep of small hole gauges:
Coat metal parts of small hole gauges
with a light film of oil to prevent rust.
Store gauges in separate containers.
Keep graduations and markings clean
Do not drop small hole gauges. Small
nicks and scratches will result in inaccurate measurements.
Figure 3-78. Measuring Hole With Telescoping
Figure 3-79. Small Hole Gauges
Figure 3-80. Measuring Hole with a Small Hole