Figure 2-17 shows how the end of the rule and one leg
of the caliper are rested on the bench top so that they are
exactly even with each other when the reading is taken.
Setting Outside and Inside Spring Calipers
To set a particular reading on an outside spring
caliper, first open the caliper to the approximate setting.
Then, as shown in figure 2-18, place one leg over the
end of the rule, steadying it with the index finger. Make
the final setting by sighting over the other leg of the
caliper squarely with the face of the rule at the reading,
and turning the knurled adjusting nut until the desired
setting is obtained.
To set an inside spring caliper to a particular
reading, place both caliper and rule on a flat surface as
shown in figure 2-19. The rule must be held squarely or
normal (90E in both directions) to the surface to ensure
accuracy. Adjust the knurled adjusting nut, reading the
setting on the rule with line-of-sight normal to the face
of the rule at the reading.
Transferring Measurements from One Caliper to
Another
To transfer a measurement from one spring caliper
to another, hold the calipers as shown in figure 2-20.
Note that one of the man's fingers is extended to steady
the point of contact of the two lower caliper legs. In this
figure the inside caliper is being adjusted to the size of
the outside caliper. As careful measurements with
calipers depend on one's sense of touch, which is
spoken of as "feel," calipers are best held lightly. When
you notice a slight drag, the caliper is at the proper
setting.
CARE OF CALIPERS
Keep calipers clean and lightly oiled, but do not
over oil the joint of firm-joint calipers or you may have
difficulty in keeping them tight. Do not throw them
around or use them for screwdrivers or pry bars. Even a
slight force may spring the legs of a caliper so that other
measurements made with it are never accurate.
Remember that calipers are measuring instruments and
must be used only for the purpose for which they are
intended.
2-7
Figure 2-17.—Setting a combination firm-joint caliper for
inside measurements.
Figure 2-18.—Setting an outside spring caliper.
Figure 2-19.—Setting an inside spring caliper.
Figure 2-20.—Transferring a measurement from an outside to
an inside caliper.
