PRECISION MEASURING AND GAGING - OD1642 - LESSON 1/TASK 2
3 To read a measurement on the vernier micrometer, use figure
38, view B and perform the following:
Read the highest figure
visible on the barrel (3) ........ 2 = 0.200 in.
Number of lines visible
between the No. 2 and the
thimble edge (4)................. 3 = 0.075 in.
The line on the thimble
that coincides with or is
nearest the revolution or
long line on
the barrel (5)................... 11 = 0.011 in.
The line on the vernier
scale that coincides
with a line on the
thimble (6)...................... 2 = 0.0002 in.
= 0.2862 in.
(c) Reading a Metric Micrometer. The same principle is applied in
reading the metric graduated micrometer, but the following changes in
graduations are used:
1 The pitch of the micrometer screw is 0.05 mm.
revolution of the spindle advances or withdraws the screw a distance equal
2 The barrel (figure 39, view A, on the following page) (1)
is graduated in millimeters from 0 to 25. It takes two revolutions of the
spindle to move the barrel 1mm.
3 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 0.5mm, or 1/100mm.
Two graduations equal
2/100mm, and so forth.
4 To read a measurement on the metric micrometer, use figure
39, view B, and perform the following:
5 Read the highest
figure visible on
the barrel (1)............... 20 = 20.0mm