Machining Fundamentals
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4.3.3 Using the Vernier Caliper
As with any precision tool, a Vernier caliper
must not be forced on the work. Slide the Vernier
assembly until the jaws nearly contact the section
being measured. Lock the clamping screw. Make the
tool adjustment with the fine adjusting nut. The
jaws must contact the work firmly, but not tightly.
Lock the slide on the beam. Carefully remove
the tool from the work and make your reading. For
precise layout work, divider and trammel point set-
tings are located on the outside measuring scale and
on the slide assembly.
Dial calipers. These direct-reading instruments
resemble Vernier calipers. They can be used to make
outside, inside, and depth measurements (with the
addition of a depth attachment). A lock permits the
tool to be employed for repetitive measurements.
See Figure 4-27.
The beam is graduated into 0.10″ increments.
The caliper dial is graduated into 100 divisions. The
reading is made by combining the division on the
beam and the dial reading.
The dial hand makes one full revolution for each
0.10″ movement. Each dial graduation, therefore,
represents 1/100 of 0.10″, or 0.001″. On the metric
version, each dial graduation represents 0.02 mm.
4.3.4 Universal Vernier Bevel Protractor
A quick review of the circles, angles, and units of
measurement associated with them will help in
understanding how to read a universal Vernier
bevel protractor.
• Degree (°)—Regardless of its size, a circle
contains 360°. Angles are also measured by
degrees.
• Minute
(′)—A
minute represents a fractional
part of a degree. If a degree is divided into
60 equal parts, each part is one minute. A
foot mark
(′)
is used to signify minutes
(e.g. 30°15’).
• Second (″)—Minutes are divided into smaller
units known as seconds. There are 60 seconds
in one minute. An angular measurement writ-
ten in degrees, minutes, and seconds appears
as 36°18’22″. This would read “36 degrees,
18 minutes, and 22 seconds.”
30.00
9.00
0.28
30.00
9.00
0.28
39.28 mm Reading is
Figure 4-25. How to read a 25-division metric-based Vernier
scale. Readings on the scale are obtained in units of two hun-
dredths of a millimeter (0.02 mm).
30.00
9.00
0.28
30.00
9.00
0.28
Reading is 39.28 mm
Figure 4-26. How to read a 50-division metric-based Vernier
scale. Each division equals two hundredths of a millimeter
(0.02 mm).
Figure 4-27. Dial calipers provide direct readings of measure-
ments. (L.S. Starrett Co.)