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Chapter 7: A. Common Gages and Measurement Instruments 63
Reading to 0.01 mm
25
0 5 10
20
15
10
5
Thimble divisions
Thimble is graduated
in 50 divisions.
Each graduation is 0.01 mm.
Major divisions
Each large graduation is 1.00 mm
Minor divisions
Each large graduation is 0.50 mm
Figure 7.5 Micrometer reading of 10.66 mm.
Reprinted with permission of the Society of Manufacturing Engineers, Manufacturing Processes and
Materials, 4th edition, copyright 2000.
Reading to 0.001 mm
Part II.A.1
Vernier divisions
Each vernier division
represents 0.001 mm
10
8
6
4
2
Major divisions
Each large graduation
is 1.0 mm
Thimble
Sleeve
40
35
30
25
20
15
0 5 10
Minor divisions
Each small graduation
is 0.50 mm
Figure 7.6 Scales of a vernier micromoter showing a reading of 10.666 mm.
Reprinted with permission of the Society of Manufacturing Engineers, Manufacturing Processes and
Materials, 4th edition, copyright 2000.
Vernier Scales
A vernier micrometer caliper, such as represented by the scales shown in Figure 7.6,
has a vernier scale on the sleeve permitting measurement to 0.001 mm. The vernier
scale shown has 10 divisions over a length equivalent to 19 divisions around the
periphery of the thimble. Thus, the difference in length of a division on the vernier
scale and two divisions on the thimble is 0.02 – (1/10)(19 × 0.01) = 0.001 mm. Thus,
the reading illustrated in Figure 7.6 is 10.00 + 0.50 + 0.16 + 0.006 = 10.666 mm.
Digital Micrometers
Micrometers with digital readouts are also available to make readings faster and
easier for inspection personnel regardless of their degree of experience. The digital