GENERAL INFORMATION
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while referring to Figure 25.
1. Read the upper half of the sleeve line and count the number of lines visible. Each upper line
equals 1mm.
2. See if the half –millimeter line is visible on the
lower sleeve line. If so, add 0.50mm to the reading
in Step 1.
3. Read the thimble mark that aligns with the sleeve
line. Each thimble mark equals 0.01mm.
NOTE
If a thimble mark does not align exactly
with the sleeve line. Estimate the amount
between the lines. For accurate readings in
two-thousandths of a millimeter (0.002mm), use a metric
vernier micrometer.
4. Add the readings from Steps 1-3.
Standard inch micrometer
The standard inch micrometer (Figure 26) is
accurate to one-thousandth of an inch or 0.001. The
sleeve is marked in 0.025 in. increments. Every fourth
sleeve mark is numbered 1,2,3,4,5,6,7,8,9. These
numbers indicate 0.100, 0.200, 0.300, and so on.
The tapered end of the thimble has 25 lines marked
around it. Each mark equals 0.001 in. One complete turn
of the thimble will align its zero mark with the first mark
on the sleeve or 0.025 in.
To read a standard inch micrometer, perform the
following steps and refer to Figure 27.
1. Read the sleeve and find the largest number
visible. Each sleeve number equals 0.100 in.
2. Count the number of lines between the numbered
sleeve mark and the edge of the thimble. Each
sleeve mark equals 0.025 in.
3. Read the thimble mark that aligns with the sleeve
line. Each thimble mark equals 0.01 in.
NOTE
If a thimble mark does not align exactly with the sleeve line, estimate the
amount between the lines. For accurate readings in ten-thousandths of an
inch (0.0001 in), use a vernier inch micrometer.
4. Add the readings from Steps 1-3.
