Machining Fundamentals
58
The micrometer caliper, also known as a “mike,”
is a precision tool capable of measuring to 0.001″ or
0.01 mm. When fitted with a Vernier scale, it will
read to 0.0001″ or 0.002 mm.
4.2.1 Types of Micrometers
Micrometers are produced in a wide variety of
models. Digital display is included in many
micrometers, making measuring easier. Some of the
most popular models are the following:
• An outside micrometer measures external
diameters and thickness, Figure 4-7.
• A chamfer micrometer will accurately
measure countersunk holes and other
chamfer-type measurements. With fastener
Figure 4-7. This digital outside micrometer can be used to
measure in both US Conventional and SI Metric units.
(Mitutoyo/MTI Corp.)
• An inside micrometer has many uses, includ-
ing measuring internal diameters of cylin-
ders, rings, and slots. The range of a
conventional inside micrometer can be
extended by fitting longer rods to the
micrometer head. The range of a jaw-type
inside micrometer is limited to 1″ or 25 mm.
The jaw-type inside micrometer has a scale
graduated from right to left. See Figure 4-8.
• A micrometer depth gage measures the depths
of holes, slots, and projections. See Figure 4-9.
The measuring range can be increased by
changing to longer spindles. Measurements
are read from right to left.
• A screw-thread micrometer has a pointed
spindle and a double-V anvil shaped to con-
tact the screw thread, Figure 4-10. It measures
the pitch diameter of the thread, which equals
the outside (major) diameter of the thread
minus the depth of one thread. Since each
thread micrometer is designed to measure
only a limited number of threads per inch, a
set of thread micrometers is necessary to mea-
sure a full range of thread pitches.
Figure 4-8. Inside micrometers. A—A conventional inside
micrometer. B—The caliper jaws on this inside micrometer allow
quick and accurate measurements. The divisions on the sleeve
are numbered in the reverse order of a conventional outside
micrometer. (L. S. Starrett Co.)
Figure 4-9. A standard micrometer depth gage.
B
A