many inches and fractions of an inch. (See fig. 2-2.)
Always reduce fractions to their lowest terms, for
example, 6/8 inch would be called 3/4 inch. A hook or
eye at the end of a tape or rule is normally part of the
first measured inch.
Bolts and Screws
The length of bolts and screws is best measured by
holding them up against a rigid rule or tape. Hold both
the rule and the bolt or screw to be measured up to your
eye level, so that your line of sight will not be in error in
reading the measurement. As shown in figure 2-3, the
bolts or screws with countersink-type heads are
measured from the top of the head to the opposite end,
while those with other types of heads are measured
from the bottom of the head.
Outside Pipe Diameters
To measure the outside diameter of a pipe, you
should use some kind of rigid rule. A wooden rule or a
steel rule is satisfactory for this purpose. As shown in
figure 2-4, line up the end of the rule with one side of
the pipe, using your thumb as a stop. Then, with the one
end held in place with your thumb, swing the rule
through an arc and take the maximum reading at the
other side of the pipe. For most purposes, the
measurement obtained by using this method is
satisfactory. It is necessary that you know how to take
this measurement, as the outside diameter of pipe is
Inside Pipe Diameters
To measure the inside diameter of a pipe with a
rule, as shown in figure 2-5, hold the rule so that one
corner of the rule just rests on the inside of one side of
the pipe. Then, with one end thus held in place, swing
the rule through an arc and read the diameter across the
maximum inside distance. This method is satisfactory
for an approximate inside measurement.
To measure the circumference of a pipe, you must
use a flexible-type rule that will conform to the shape of
the pipe. A fabric or steel flexible tape rule is adaptable
to this job. When measuring the pipe, make sure the
tape is wrapped squarely around the axis of the pipe to
ensure that the measurement will not be more than the
Figure 2-2.Measuring with and reading a common rule.
Figure 2-3.Measuring the length of a bolt or screw.
Figure 2-4.Measuring the outside diameter of a pipe.
Figure 2-5.Measuring the inside diameter of a pipe.