The vernier caliper (fig. 2-43) consists of an L-
shaped member with a scale engraved on the long
shank. A sliding member is free to move on the bar
and carries a jaw that matches the arm of the L. The
vernier scale is engraved on a small plate that is
attached to the sliding member.
The vernier caliper can provide very accurate
measurements over a large range. It can be used for
both internal and external measurement. Some
models have a depth reading feature in addition to
the internal and external measurements.
In using the vernier caliper, you must be able to
read a vernier scale. Figure 2-44 shows a bar 1 inch
long divided by graduations into 40 parts, so each
graduation indicates one-fortieth of an inch (0.025
inch). Every fourth graduation is numbered; each
number indicates tenths of an inch (A x 0.025 inch).
The vernier, which slides along the bar, is graduated
into 25 divisions; these together are as long as 24
divisions on the bar. Each division of the vernier is
0.001 inch smaller than each division of the bar.
Verniers that are calibrated as explained previously
are known as English-measure verniers. The metric-
measure vernier is read the same, except that the
units of measurement are in millimeters.
Taking Outside Measurements
with the Vernier Caliper
To measure the distance between outside
surfaces or the outside diameter of a round object
(such as sound stock or a shaft), steady the object
with one hand and hold the caliper in one hand as
Figure 2-44.English-measure vernier scale.
shown in figure 2-45. In the figure, the clamping
screws are at A and B; the horizontal adjustment
screw nut is at C. With A and B loose, slide the
movable jaw toward the piece being measured until it
is almost in contact. Then tighten clamping screw A
to make the fine adjusting nut C operative. Using the
fine adjusting nut, adjust the movable jaw to the
proper feel, then secure the setting by tightening
clamping screw B. The reading can then be taken as
Figure 2-45.Taking an outside measurement with
a vernier caliper.
Figure 2-43.Vernier caliper.