Reading a depth micrometer. When reading a
depth micrometer, you will notice that the graduations
on the sleeve are numbered in the opposite direction of
those on an outside or inside micrometer. When you are
reading a depth micrometer, the distance to be
measured is the value that is covered by the thimble.
See figure 2-30; consider the reading shown. The
thimble edge is between the numbers 4 and 5. This
shows a value of at least 0.400 inch on the sleeve's
major divisions. The thimble also covers the first minor
division on the sleeve; this has a value of 0.025 inch.
The value shown on the thimble circumference scale is
0.010 inch. Adding these three values together results
in a total of 0.435 inch, or the total distance that the end
of the extension rod has traveled from the base. This
measurement added to the length of the extension rod
used gives you the total depth of the hole, recess, or
groove that was measured.
Figure 2-28.Inside micrometer set.
Figure 2-29.Using a depth micrometer.
Figure 2-30.Depth micrometer sleeve and thimble scales.