Chapter 4 Measurement
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4.3 VERNIER MEASURING TOOLS
The Vernier principle of measuring was named
for its inventor, Pierre Vernier, a French mathe-
matician. The Vernier caliper can make accurate
measurements to 1/1000″ (0.001″) and 1/50 mm
(0.02 mm). See Figure 4-20.
The following measuring instruments may
include a Vernier scale:
• Height and depth gages are used for layout
work and to inspect the locations of features.
See Figure 4-22.
• Gear tooth calipers are used to measure gear
teeth and threading tools, Figure 4-23.
• Universal Vernier bevel protractors are used
for the layout and inspection of angles,
Figure 4-24.
Vernier measuring tools, with the exception of
the Vernier bevel protractor, consist of a graduated
beam with fixed jaw or base and a Vernier slide
assembly. The Vernier slide assembly is composed
of a movable jaw or scribe, Vernier plate, and clamp-
ing screws. The slide moves as a unit along the
beam.
Unlike other Vernier measuring tools, the beam
of the Vernier caliper is graduated on both sides.
One side is for making outside measurements, the
other for inside measurements. Many of the newer
Vernier measuring tools are graduated to make both
inch and millimeter measurements.
Figure 4-19. Micrometers must be treated carefully. Roll the
micrometer thimble on the palm of your hand if the instrument
must be opened or closed a considerable distance.
Figure 4-20. Vernier calipers can be used to make very accu-
rate measurements. A—Standard Vernier caliper. B—Modern
digital calipers are easier to read than mechanical instruments.
The design of the tool permits measurements to
be made over a large range of sizes. It is manufac-
tured as a standard item in 6″, 12″, 24″, 36″, and 48″
lengths. SI Metric Vernier calipers are available in
150 mm, 300 mm, and 600 mm lengths. The 6″, 12″,
150 mm, and 300 mm sizes are most commonly
used. Unlike the micrometer caliper, the Vernier
caliper can be used for both inside and outside mea-
surements, Figure 4-21.
Figure 4-21. Vernier calipers can be used to make both internal
and external measurements. (L. S. Starrett Co.)
A
B