PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2
2 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 holding a part too large to be held in one hand is
shown in figure 40, view B, on the previous page. The frame is held by one
hand to position it and 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.
3 To measure a
shaft as shown in figure 40, view C, the frame
is held by one hand while
the thimble is operated by the other.
In
measuring a cylindrical part
with a micrometer, it is necessary to "feel"
the setting to be sure that
the spindle is on the diameter, and also to
check the diameter in several
places to determine the out-of-roundness.
4 For measuring very large diameters, micrometer calipers are
made in various sizes up to 168 inches. A pulley is being checked (figure
41)
FIGURE 41.
MEASURING LARGE DIAMETERS.
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