Glossary of Technical Terms 615
lathe dog: A device for clamping work so that
it can be machined between centers. (Ch. 14)
lay: The direction of the predominant tool
marks, grain, or pattern of surface roughness.
(Ch. 30)
lay out: The process of locating and scribing
points for machining and forming operations.
(Ch. 6)
layout dye: A coating applied to metal to make
layout lines more visible. (Ch. 6)
lead: The distance a nut will advance on a
screw in one revolution. (Ch. 16)
least material condition (LMC): The condition
where a feature of size contains the least
amount of material within the stated limits.
(Ch. 4)
linear interpolation: Straight-line movement
(in the context of CNC programming).
(Ch. 23)
loading: A process where small pieces of
metal clog the surface of the grinding wheel
causing ineffi cient cutting action. (Ch. 13)
location geometric tolerances: Tolerances
used for the purpose of locating features
from datums, or for establishing coaxiality
or symmetry. (Ch. 4)
low-carbon steels: Steel that contains less
than 0.3%, or 30 points, or carbon. Low-
carbon steel does not contain enough carbon
to be hardened. However, case hardening
is possible if the surface is exposed to an
external source of carbon during the process.
Also called mild steel. (Ch. 28)
M
machine control unit (MCU): Also simply
called a control, the part of a CNC machine
that reads the CNC program from memory
and translates it into the electronic signals
needed for machine operation. (Ch. 23)
machine home: For purposes of CNC
programming, the location of the table and
spindle on the CNC machine. (Ch. 24)
machine shield: A type of barrier on a
machine that blocks fl ying chips and
splashing cutting fl uids or coolants from
escaping and harming the machinist. (Ch. 3)
machine tools: That class of machines which,
taken as a group, can reproduce themselves.
(Ch. 1)
machining center: A CNC milling machine
equipped with an automatic tool changer
(ATC). (Ch. 22)
machinist: A person who is skilled in the use
of machine tools and is capable of making
complex machine setups. (Ch. 1)
magnetic forming: A type of high-energy-rate
forming in which the magnetic force from a
specially shaped induction coil provides the
pressure needed to shape the material. Also
known as “electromagnetic forming” and
“magnetic pulse forming.” (Ch. 33)
magnetic particle inspection: A
nondestructive testing technique that uses
iron particles and induced magnetic fi elds
to detect fl aws on or near the surface of
ferromagnetic (iron-based) materials. (Ch. 27)
major diameter: The largest diameter of a
thread measured perpendicular to the axis.
(Ch. 16)
mandrel: A slightly tapered, hardened steel
shaft that supports work machined between
centers. (Ch. 15)
manual data input (MDI): A method of
programming CNC programs by entering the
program codes at the machine control unit.
(Ch. 23)
maximum material condition (MMC): The
condition where a feature contains the
maximum amount of material within the
stated limits. (Ch. 4)