USE/CARE OF HANDTOOLS & MEASURING TOOLS - OD1621 - LESSON 3/TASK 1
(2) Reading Metric Micrometer.
The same principle is applied in
reading the Metric graduated micrometer, but the following changes in
graduations should be noted to avoid confusion:
(a) The pitch of the micrometer screw is 0.5 mm. One revolution
of the spindle advances or withdraws the screw a distance equal to 0.5 mm.
(b) The barrel is graduated in millimeters from 0 to 25; it takes
two revolutions of the spindle to move 1 mm.
(c) The thimble is graduated in 50 divisions with every fifth line
(d) 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
(3) Adjusting Micrometer Caliper to Work.
(a) Figure 193, view A, on the following page, shows the proper
way to hold a micrometer caliper in checking a small part. Hold the part in
one hand. Hold the micrometer in the other hand so that the thimble rests
between the thumb and the forefinger.
The third finger is then in a
position to hold the frame against the palm of the hand.
The frame is
supported in this manner which makes it easy to guide the work over the
anvil. The thumb and forefinger are in position to turn the thimble, either
directly or through the ratchet, and move the spindle over against the work.
(b) On larger work, it is necessary to have the work stationary
and positioned to permit access to the micrometer.
The proper method of
holding a micrometer when checking a part too large to be held in one hand
is shown in figure 193, view B. The frame is held by one hand to position
it and to locate it square to the measured surface. The other hand operates
the thimble, either directly or through the ratchet.
A large flat part
should be checked in several places to determine the amount of variation.
(c) To gage a shaft as shown in figure 193, view C, the frame is
held by one hand while the thimble is operated by the other. In gaging a