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Aviation Boatswains Mate E - Aviation theories and other practices | Next
MICROMETER-READING EXERCISE |
REVIEW QUESTIONS
Q1.
Identify the different types of measuring tools.
Q2.
Describe the uses of different types of
measuring tools.
Q3.
Describe the proper care of measuring tools.
PRECISION MEASURING EQUIPMENT
LEARNING OBJECTIVES: Identify the
different types of precision measuring tools.
Describe the uses of different types of
precision measuring tools. Describe the proper
care of measuring tools. Maintain inventory
and accountability of precision equipment.
In much wider use by ABEs than even common
calipers are the various types of micrometer calipers.
As was stated earlier, you can use micrometer calipers
to take accurate measurements to the nearest one
ten-thousandth
of
an
inch.
However,
in
most
applications a measurement to the nearest one-
thousandth of an inch is considered acceptable
accuracy. These measurements are expressed or written
as a decimal (0.0001, 0.001, 0.01), so you must know
how to read and write decimals.
TYPES OF MICROMETER CALIPERS
There are three types of micrometer calipers,
commonly called micrometers or simply mikes, used
throughout the Navy: the outside micrometer, including
the screw thread micrometer; the inside micrometer;
and the depth micrometer. (See fig. 2-21.) The outside
micrometer is used for measuring outside dimensions,
such as the outside diameter of a piece of round stock or
the thickness of a piece of flat stock. The screw thread
micrometer is used to determine the pitch diameter of
screws. The inside micrometer is used to measure the
inside diameter of a cylinder or hole. The depth
micrometer is used for measuring the depth of a hole or
recess.
Outside Micrometer
The nomenclature of an outside micrometer is
illustrated in figure 2-22.
The sleeve and thimble scales of a micrometer (fig.
2-23)
have
been
enlarged
and
laid
out
for
demonstration. To understand these scales, you need to
know that the threaded section on the spindle, which
revolves, has 40 threads per inch. Therefore, every time
the thimble completes a revolution, the spindle
advances or recedes 1/40 inch, or 0.025 inch.
Note the horizontal line on the sleeve is divided into
40 equal parts per inch. Every fourth graduation is
numbered 1, 2, 3, 4, and so on, representing 0.100 inch,
0.200 inch, and so on. When you turn the thimble so its
edge is over the first sleeve line past the 0 on the thimble
scale, the spindle has opened 0.025 inch. If you turn the
spindle to the second mark, it has moved 0.025 inch
plus 0.025 inch, or 0.050 inch.
2-8
Figure 2-21.—Common types of micrometers.
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