Glossary of Technical Terms 609
critical temperature: The temperature at
which a metal’s crystal structure changes.
Most heat treatment processes require that
the metal be heated to its critical temperature.
(Ch. 29)
cross slide: A part of a machine tool that
permits the carriage to make transverse tool
movements. (Ch. 14)
cryogenic: Having or associated with
extremely low temperatures. The crygogenic
temperature range is generally considered
to be –300°F to –460°F (–184°C to –273°C).
(Ch. 33)
cutting fluid: A liquid used to cool and
lubricate a cutting tool to improve the
quality of the surface fi nish. There are four
basic types of cutting fl uids: mineral oils,
emulsifi able (water-based) oils, chemical and
semichemical cutting fl uids, and gaseous
fl uids. (Ch. 10)
cutting speed: In reference to milling machines,
the distance, measured in feet or meters, that a
point (tooth) on the cutter’s circumference will
move in one minute. In reference to lathes, the
distance the work moves past the cutting tool,
expressed in feet per minute (fpm) or meters
per minute (mpm). Measuring is done on the
circumference of the work. In reference to
drilling machines, it is the speed at which the
cutting tool rotates. (Ch. 12, 14, 18)
cyanoacrylate quick setting adhesive: A
bonding agent known by such names as
Eastman 910™, Super Glue™, and Crazy
Glue™. It is used to hold matching metal
sections together while they are being
machined. (Ch. 8)
cylindricity: A form tolerance identifi ed by
a radius tolerance zone establishing two
perfectly concentric cylinders within which
the actual surface must lie. (Ch. 4)
D
datum: A theoretically exact point, axis, line, or
plane. (Ch. 4)
dedendum: The portion of a gear tooth
between pitch circle and root circle; it is equal
to addendum plus clearance. (Ch. 19)
depth of cut: Refers to the distance the
cutter is fed into the work surface. The
depth of cut varies greatly with lathe
condition, material hardness, speed, feed,
amount of material to be removed, and
whether it is to be a roughing or fi nishing
cut. (Ch. 14)
destructive testing: A quality control process
in which the part being tested is destroyed by
the testing process. (Ch. 27)
dial indicator: An instrument used for
centering and aligning work on machine
tools, checking for eccentricity, and
inspecting. There are two types of indicators:
balanced indicators take measurements on
either side of a zero line, while continuous
indicators read from zero in a clockwise
direction. (Ch. 5)
diametral pitch: The ratio of the number of
gear teeth to the number of inches of pitch
diameter. (Ch. 19)
diamond-edge band: A specially designed
band machining tool for cutting material
that is diffi cult or impossible to cut with a
conventional toothed blade. The diamonds
are only on the front edge of the band, where
the cutting is accomplished. (Ch. 21)
dielectric fluid: In electrical discharge
machining, a fl uid that forms a
nonconductive barrier between the electrode
and the work at the arc gap. (Ch. 31)
dimensions: Sizes or measurements needed to
produce a part. (Ch. 4)