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TM 9-254
Section II. MEASURING TECHNIQUES AND SCRIBING
4-3.
General.
Measuring tools are designed for measuring work accurately. They include calibrated measuring tools such as (rules,
precision tapes, and micrometers) designed to measure distances in accordance with one of several standards of
measurement.
4-4.
Types of Rules.
Steel rules (fig. 4-17) are available from a fraction of an inch in length up to 4 feet or more, but in machine shops the steel
machinist rule is the one most commonly used. There are also several standard systems of graduations. In the English
system, rules are graduated in 10ths, 20ths, 50ths, and 100ths; 16ths, 32nds, and 64ths of an inch. In the Metric system,
rules are graduated in millimeters and one-half millimeters. Some steel rules have four scales, two on each side (one
graduated in 32nds and the other in 64ths) with the scales on the reverse side running in the opposite direction. There are
rules made that have both an inch scale and millimeter scale, which makes this type rule adaptable to work involving both
systems of measure. Another feature on some rules is a scale etched across the end of the rule which facilitates
measurement in restricted places.
Figure 4-17. Types of Steel Rules
4-14
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