Glossary of Technical Terms 607
chemical blackening: A process that
chemically bonds a black oxide coating to
the surface of ferrous metals. The resulting
coating improves corrosion and wear
resistance, reduces glare from the surface,
and improves the adhesion of subsequent
layers of paint or other coatings. (Ch. 30)
chemical blanking: A variation of the
chemical milling operation that results in
the removal of metal from certain areas by
chemical action. Commonly used to cut parts
out of ultrathin materials. (Ch. 32)
chemical cutting fluid: Cooling and lubricating
liquid that contains no oil. Because they
are not actually fl uids (graphite, mica, and
white lead are examples), a wetting agent is
often added to provide lubricating qualities.
Compare with cutting fl uid. (Ch. 10)
chemical machining: A category of processes
that use chemicals, usually in an aqueous
(with water) solution, to etch away selected
portions of material. (Ch. 32)
chemical milling: A process that uses a
masking technique and a chemical etchant to
remove metal selectively from relatively large
surface areas. (Ch. 32)
chipbreaker: A small groove cut into the face
of a lathe tool near the cutting edge to break
chips into small pieces. (Ch. 14)
chipless machining: A manufacturing process
that forms metal wire or rod into desired
shapes using a series of dies. Also called cold
forming and cold heading. (Ch. 33)
circular interpolation: Movement in a
circular pattern (in the context of CNC
programming). (Ch. 23)
circularity: A form tolerance that is characterized
by any given cross section taken perpendicular
to the axis of a cylinder or cone, or through the
common center of a sphere. (Ch. 4)
circular pitch: The distance from the center of
one gear tooth to the center of the next tooth,
measured along the pitch circle. (Ch. 19)
circular runout: A type of runout that
provides control of single circular elements of
a surface. (Ch. 4)
class of fit: Standard working tolerances for
thread accuracy, indicated by the last number
on a thread description. Fits for inch-based
threads are as follows: Class 1, loose fi t; Class
2, free fi t; Class 3, medium fi t; and Class 4,
close fi t. (Ch. 7)
climb milling: A milling technique in which
the teeth of a cutting tool advance into the
work in the same direction as the feed. Also
known as “climb cutting.” (Ch. 18)
closed-loop system: A system in which
feedback is provided to the controlling
mechanism; used with servo motors in CNC
systems to provide feedback to the controllers
regarding the position of the axis they are
driving. (Ch. 22)
CNC milling center: A traditional milling
machine with built-in CNC capabilities. (Ch. 22)
cold circular saw: A tool that uses a circular,
toothed blade capable of producing very
accurate cuts. Large cold circular saws can
be used to sever round metal stock up to 27”
(675 mm) in diameter. (Ch. 11)
cold finished steel: Steel that has been
“pickled” or treated with a dilute acid
solution to remove its oxide coating. After
pickling, the steel is drawn or rolled to
fi nished size and shape while cold. Cold
fi nished steel is characterized by a smooth,
bright fi nish. (Ch. 28)
cold forming: A manufacturing process that
forms metal wire or rod into desired shapes
using a series of dies. Also called chipless
machining and cold heading. (Ch. 33)