TM 1-1500-204-23-9
(4) Conversion for inside measurement. Most
vernier calipers read OUTSIDE on one side and INSIDE
on the other side. If a scale is not marked, and an
inside measurement must be taken, read the scale as
for an outside measurement. Then add the measuring
point allowance by referring to the instructions of the
manufacturer or the following:
SIZE OF
ENGLISH
METRIC
CALIPER
MEASURE
MEASURE
6 inch or 150 mm
0.250 inch
6.35 mm
12 inch or 300 mm
0.300 inch
7.62 mm
24 inch or 600 mm
0.300 inch
7.62 mm
36 inch or 600 mm
0.500 inch
12.70 mm
(5) Reading a metric caliper. The following
paragraphs describe the procedure for reading a metric
caliper (see figure 3-33).
(a) Steel rule. The steel rule (3) is divided
into centimeters (cm) (1). The longest lines represent
10 millimeters (mm) each. Each millimeter is divided
into quarters.
(b) Vernier scale. The vernier scale (4) is
divided into 25 parts and is numbered 0, 5, 10, 15, 20,
and 25.
(c) Reading the measurement. Read the
measurement as outlined below:
Read the total number of millimeters (2) to
the left of the vernier zero index (6) and
record............................................ 32.00 cm
Read the number of quarters (5) between
the millimeter mark and the vernier zero
index (6) and record ....1 quarter = 0.25 mm
Read the highest line on the vernier scale
(4) which lines up with a line on the top
scale (7) and record ......................0.18 mm
Total all preceding measurements 32.43 mm
The measurement, therefore, is 32.43 millimeters
Figure 3-33. Reading a Metric Caliper
3-13
