TM 9-243
TYPES AND USES
Micrometers are instruments used to measure distances
to the nearest one-thousandth of an inch. The
measurements usually expressed or written as a
decimal. There are three types of micrometers which
are commonly used: the outside micrometer, the inside
micrometer, and the depth micrometer.
OUTSIDE MICROMETER
Outside micrometers are used to measure an outside
distance or diameter to an accuracy of .001 of an inch.
INSIDE MICROMETER
Inside micrometers are used to measure an inside
diameter to within an accuracy of .001 in. (for
remaining one-half inch,
see page 7-3) unlike
outside
micrometers,
inside
micrometer
thimbles have a range
of only .500
of an inch. For remaining one-half inch spacer provided
with the micrometer.
DEPTH MICROMETERS
Depth micrometers are used to measure depths to an
accuracy of .001 inches.
SELECTING THE PROPER MICROMETER
The types of micrometers commonly used are made so that the
longest movement possible between the spindle and the anvil is
1 inch. This movement is called the "range." The frames of
micrometers, however, are available in a wide variety of sizes,
from 1 inch up to as large as 24 inches. The range of a 1 inch
micrometer is from 0 to 1 inch. In other words, it can be used to
work where the part to be measured is 1 inch to 2 inches, and
will measure only work between 1 and 2 inches thick. A 6-inch
micrometer has arrange from 5 to 6 inches, and will measure
only work between 5 and 6 inches thick. It
7-2 Change 3
