Chapter 4 Measurement
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4.2.5 Reading a Metric Vernier Micrometer
Metric Vernier micrometers are read in the same
way as standard metric micrometers. However,
using the Vernier scale on the sleeve, an additional
reading of two-thousandths of a millimeter can be
obtained, Figure 4-15.
results as the ratchet stop but permits one-
handed use of the micrometer.
7.000 mm
0.500 mm
7.000
0.500
0.310
0.004
7.814 mm
0.310 mm
0.004 mm
Reading is
Figure 4-15. Reading a metric-based Vernier micrometer
caliper. To the regular reading in hundredths of a millimeter
(0.01), add the reading from the Vernier scale that coincides
with a line on the thimble. Each line on the Vernier scale is equal
to two thousandths of a millimeter (0.002 mm).
4.2.6 Using the Micrometer
The proper way to hold a micrometer when
making a measurement is shown in Figure 4-16. The
work is placed into position, and the thimble
rotated until the part is clamped lightly between the
anvil and spindle. Guard against excessive pressure,
which will cause an erroneous reading. Some
micrometers have features to help regulate pressure:
• A ratchet stop is used to rotate the spindle.
When the pressure reaches a predetermined
amount, the ratchet stop slips and prevents
further spindle turning. Uniform contact
pressure with the work is ensured, even if dif-
ferent people use the same micrometer. Refer
again to Figure 4-11.
• A friction thimble may be built into the upper
section of the thimble. This produces the same
Figure 4-16. Proper technique of handling a micrometer.
A—Use very light pressure when turning the thimble. B—When
the piece being measured must also be held, position the
micrometer as shown, with a finger in the micrometer frame.
B
A