Machining Fundamentals 608
cold heading: A manufacturing process that
forms metal wire or rod into desired shapes
using a series of dies. Also called chipless
machining and cold forming. (Ch. 33)
column and knee milling machine: So
named because of the parts that provide
movement to the workpiece. It consists
of a column that supports and guides the
knee in vertical (up and down/Z-axis)
movement, and a knee that supports the
mechanism for obtaining table movements.
These movements are transverse (in and
out/Y-axis) and longitudinal (back and
forth/X-axis). (Ch. 18)
combustible material: A solid, liquid,
or gas that is capable of burning.
Combustible materials are classified into
four categories: Class A fires involve
ordinary combustible materials (paper,
wood, textiles); Class B fires involve
flammable liquids and grease; Class C fires
involve electrical components; and Class
D fires involve flammable metals, such as
magnesium and lithium. (Ch. 3)
comment code: Text in a CNC program
that is enclosed in parentheses and is
not read by the controller. Instead, the
text appears on the controller screen as
a reminder or prompt for the machine
operator. (Ch. 24)
compound rest: A slide in the lathe located
above a base cross-slide. The upper slide can
be revolved to any required angular position.
(Ch. 14)
computer numerical control (CNC): A system
in which a program is used to precisely
position tools or the workpiece and to carry
out the sequence of operations needed to
produce a part. (Ch. 1)
computer integrated manufacturing (CIM):
A manufacturing system with computer-
controlled machinery and adaptive tooling,
which allows the system to be quickly
adapted to changes in the product or the
manufacturing process. Also called a fl exible
manufacturing system. (Ch. 26)
concentricity: The condition where the axes
of all cross-sectional elements of a cylindrical
surface are common with the axis of a datum
feature. (Ch. 4)
conventional milling: A type of milling
operation where the work is fed into
the rotation of the cutter. Also know as
"up-milling." (Ch. 18)
conversational language: An interface on
CNC machines that allows the operator
to select operations from menus, without
having to understand G-code. (Ch. 22)
coordinate measuring machine (CMM):
An instrument that makes precise
measurements electronically. A CMM
can be used manually or programmed to
check any number of individual reference
points on the object against specifications.
(Ch. 27)
coordinate system: A method of locating
specifi c points or positions in three-
dimensional space. (Ch. 22)
counterboring: The process of cutting a
cylindrical enlargement of a hole to a given
depth and diameter to allow bolt heads to
be fl ush with the surface of the workpiece.
(Ch. 12)
countersinking: The process of chamfering a
hole to receive a fl athead screw. (Ch. 12)
creep grinding: A surface grinding operation
that is often performed in a single pass with
an unusually large depth of cut. (Ch. 20)