General
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Micrometers that cover a wider range of
measurements are available. These use
a large frame with interchangeable
anvils of various lengths. This type of
micrometer offers a cost savings, but its
overall size may make it less convenient.
When reading a micrometer, numbers
are taken from different scales and
added together. The following sections
describe how to adjust, care for and read
the measurements of various types of
outside micrometers. For accurate
results, properly maintain the measuring
surfaces of the micrometer. There
cannot be any dirt or burrs between the
tool and the measured object. Never
force the micrometer to close around an
object. Close the micrometer around the
highest point so it can be removed with a
slight drag.
Adjustment
Before using a micrometer, check its
adjustment as follows:
1. Clean the anvil and spindle faces.
2. To check a 0-1 in. or 0-25 mm
micrometer:
• Turn the thimble until the spindle
contacts the anvil. If the
micrometer has a ratchet stop,
use it to ensure that the proper
amount of pressure is applied.
• If the adjustment is correct, the 0
mark on the thimble will align
exactly with the 0 mark on the
sleeve line. If the marks do not
align, the micrometer is out of
adjustment. Follow the
manufacturer’s instructions to
adjust the micrometer.
3. To check a micrometer larger than 1
in. or 25mm use the standard gauge
Supplied by the manufacturer. A
standard gauge is a steel block, disc or
rod that is machined to an exact size.
• Place the standard gauge between the
spindle and anvil, and measure its
outside diameter or length. If the
micrometer has a ratchet stop, use it to
ensure that the proper amount of
pressure is applied.
• If the adjustment is correct, the 0 mark
on the thimble will align exactly with
the 0 mark on the sleeve line. If the
marks do not align, the micrometer is
out of adjustment.
• Follow the manufacturer’s instructions
to adjust the micrometer.
Care
Micrometers are precision instruments. They
must be used and maintained with great care.
Note the following:
1. Store micrometers in protective cases
or separate padded drawers in a tool
box.
2. When in storage, make sure the
spindle and anvil faces do not contact
each other or another object. If they
do, temperature changes and
corrosion may damage the contact
faces.
3. Do not clean a micrometer with
compressed air. Dirt forced into the
tool will cause wear.
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