PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2
k.
Vernier Calipers.
(1) General.
This type of caliper (figure 44) uses the vernier
scale. The vernier scale consists of a short auxiliary scale usually having
one more graduation in the same length as the longer main scale.
The
vernier caliper consists of an L-shaped frame, the end of which is a fixed
jaw; the long arm of the L is inscribed with the main true scale or fixed
scale. The sliding jaw carries the vernier scale on either side. The scale
on the front side is for outside measurements; the scale on the back is for
inside measurements.
On some vernier calipers, the metric system of
measurement is placed on the back side of the caliper in lieu of a scale
used for inside measurements. In such cases, add the thickness of the nibs
to the reading when making inside measurements. The tips of the jaws are
formed so that inside measurements can be taken.
The thickness of the
measuring points is automatically compensated for on the inside scale. The
length of the jaws will range from 1 1/4 inches to 3 1/2 inches, and the
minimum inside measurement with the smallest caliper is 1/4 inch or 6
millimeters. Vernier calipers are made in standard sizes of 6, 12, 24, 36,
and 48 inches, and 150, 300, 600, and 900 millimeters.
The jaws of all
vernier calipers, except the larger sizes, have two center points, which are
particularly useful in setting the dividers to the exact dimensions.
FIGURE 44.
VERNIER CALIPER.
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