Use and Care of Hand Tools and Measuring Tools,
shows the calipers most commonly used in
NAVEDTRA 12085 chapter 3.
Outside calipers for measuring outside
diameters are bow-legged; those used for inside
diameters have straight legs with the feet turned
The main disadvantage of using ordinary
outward. You adjust calipers by pulling or
calipers is that they do not give a direct reading
pushing the legs to open or close them. You can
of a caliper setting. As explained earlier, you must
make fine adjustment on calipers by tapping one
measure a caliper setting with a rule. To overcome
leg lightly on a hard surface to close them or by
this disadvantage, use slide calipers (fig. 3-17).
turning them upside down and tapping on the
This instrument is occasionally called a caliper
joint end to open them.
Spring-joint calipers have the legs joined
Slide calipers can be used for measuring out-
by a strong spring hinge and linked together
side, inside, and other dimensions. One side of
by a screw and adjusting nut. For measur-
the caliper is used as a measuring rule, while the
ing chamfered cavities (grooves), or for use
scale on the opposite side is used in measuring out-
over flanges, transfer calipers are available.
side and inside dimensions. Graduations on both
They are equipped with a small auxiliary
scales are in inches and fractions. A locking screw
leaf attached to one of the legs by a screw.
holds the slide caliper jaws in position during use.
The measurement is made as with ordinary
Stamped on the frame are the words IN and OUT.
calipers; then the leaf is locked to the leg.
You use these in reading the scale while making
The legs may be opened or closed as needed
inside and outside measurements, respectively.
to clear the obstruction, and then brought
back and locked to the leaf again, which restores
them to the original setting.
A different type of caliper is the her-
A vernier caliper (fig. 3-18) consists of an
maphrodite, sometimes called an odd-leg caliper.
L-shaped member with a scale engraved on the
This caliper has one straight leg ending in a sharp
long shank. A sliding member is free to move on
point, sometimes removable, and one bow leg.
the bar and carries a jaw which matches the arm
of the L. The vernier scale is engraved on a small
locating the center of a shaft or for locating a
plate that is attached to the sliding member.
Perhaps the most distinct advantage of the
You can find out more about how to
vernier caliper, over other types of caliper, is the
u s e and to care for simple calipers in
Figure 3-17.--Slide caliper.