TM 9-243
READING A METRIC MICROMETER
The same principle is applied in reading the metric
graduated micrometer, but the following changes in
graduations are used:
The pitch of the micrometer screw is 0.05 mm. One
revolution of the spindle advances or withdraws the
screw a distance equal to 0.5 mm.
The barrel (1) is graduated in millimeters from 0 to 25. It
takes two revolutions of the spindle to move the barrel
1 mm.
The thimble (2) is graduated in 50 divisions with every
fifth line being numbered.
Rotating the thimble from one graduation to the next
moves the spindle 1/50 of 0.5 mm, or 1/100 mm. Two
graduations equal 2/100 mm, and so forth.
CARE OF MICROMETERS
TO READ MEASUREMENT AS SHOWN ABOVE:
Read highest figure
visible on barrel (1) . . . . . . . . . . . . . . 20 = 20.0 mm
Number of lines visible
between the No. 20 and
thimble edge (2) . . . . . . . . . . . . . . . . . . .2 = 2.0 mm
The line on the thimble
that coincides with or
has passed the
revolution or long line
in the barrel (3)
. . . . . . . . . . . 36=36/100 (.36) mm
NOTE
Remember that 1 revolution is 0.5 mm. It
takes 2 revolutions to move 1 mm.
Measurement reading . . . . . . . . . . . TOTAL 22.36 mm
1.
Coat metal parts of all micrometers with a light coat
3.
Keep graduations and markings on all micrometers
of oil to prevent rust.
clean and legible.
2.
Store micrometers in separate containers provided
4.
Do not drop any micrometer. Small nicks or
by manufacturer.
scratchescan cause inaccurate measurements.
7-6
