Chapter 4 Measurement
65
into 40 equal parts. Each graduation is 1/40″
(0.025″). Every fourth division, representing 0.100″,
is numbered.
There are 25 divisions on the Vernier plate.
Every fifth line is numbered: 5, 10, 15, 20, and 25.
The 25 divisions occupy the same space as 24 divi-
sions on the beam. This slight difference, equal to
0.001 (1/1000″) per division, is the basis of the
Vernier principle of measuring.
To read a 25-division Vernier plate measuring
tool, note how many inches (1, 2, 3, etc.), tenths
(0.100, 0.200, etc.), and fortieths (0.025, 0.050, or
0.075) there are between the “0” on the Vernier scale
and the “0” line on the beam, then add them. Then
count the number of graduations (each graduation
equals 0.001″) that lie between the “0” line on the
Vernier plate and the line that coincides (corre-
sponds exactly) with a line on the beam. Only one
line will coincide. Add this to the above total for the
reading.
The “0” line on the Vernier plate is:
Past the 2: 2 1 = 2.000
Past the 3: 3 0.100 = 0.300
Plus 2 graduations: 2 0.025 = 0.050
Plus 18 Vernier scale
graduations: 18 0.001 = 0.018
Total reading = 2.368″
On the 50-division Vernier plate, every second
graduation between the inch lines is numbered, and
equals 0.100″. The unnumbered graduations equal
0.050″.
The Vernier plate is graduated into 50 parts,
each representing 0.001″. Every fifth line is num-
bered: 5, 10, 15 . . . 40, 45, and 50.
To read a 50-division Vernier measuring tool,
first count how many inches, tenths (0.100), and
twentieths (0.050) there are between the “0” line on
the beam, and the “0” line on the Vernier plate. Then
add them. Then count the number of 0.001 gradua-
tions on the Vernier plate from its “0” line to the line
that coincides with a line on the beam. Add this to
the above total.
Figure 4-24. A universal Vernier bevel protractor is used to
accurately measure angles. (L. S. Starrett Co.)
0.300
0.050
0.018
2.000
2.000
0.300
0.050
0.018
Reading is 2.368″
The “0” line on the Vernier plate is:
Past the 2: 2 1.000 = 2.000
Past the 2: 2 0.100 = 0.200
Plus one graduation: 1 0.050 = 0.050
Plus 15 Vernier scale
graduations: 15 0.001 = 0.015
Total reading = 2.265″
4.3.2 Reading a Metric-Based Vernier Scale
The principles used in reading metric Vernier
measuring tools are the same as those used for
US Conventional measure. However, the readings
on the Vernier scale are obtained in 0.02 mm preci-
sion. A 25-division Vernier scale is illustrated in
Figure 4-25, while a 50-division scale is described in
Figure 4-26.
2.000
0.200
0.050
0.015
2.000
0.200
0.050
0.015
Reading is 2.265″