Glossary of Technical Terms 613
geometric tolerance: A general term that
refers to tolerances that control form, profi le,
orientation, or location of a feature. (Ch. 4)
glazing: A process where the grains of a
grinding wheel dull before they can wear
away, leaving a shiny surface and causing
ineffi cient cutting action. (Ch. 13)
graduations: Lines that indicate measurement
points on tools and machine dials. (Ch. 5)
grinding: An operation that removes material
by rotating an abrasive wheel or belt against
the work. (Ch. 13)
grinding machine: A machine that removes
material from work by means of a rotating
grinding wheel made of abrasive particles or
an abrasive belt. Also known as a “grinder.”
(Ch. 1)
grooving: A turning operation of cutting
a groove or recess into a workpiece to
terminate a thread or provide adequate
clearance for mating parts. (Ch. 14)
H
hardening: A heat treatment that reduces the
ductility of steel. It is performed by heating
metal to the proper temperature and then
quenching it. (Ch. 29)
headstock: On a lathe, the structure that
contains the spindle to which various work-
holding attachments are fi tted. (Ch. 14)
heat treatment: The controlled heating
and cooling of a metal or alloy to obtain
certain desirable changes in its physical
characteristics. These changes include
improving resistance to shock, developing
toughness, and increasing wear resistance
and hardness. (Ch. 29)
high-carbon steels: Steel that contains 0.6%–1.5%
carbon. It is used in products that must be heat
treated. (Ch. 28)
high-energy-rate forming (HERF): A
manufacturing process in which a material is
formed around a die by the rapid application
of extreme pressures. (Ch. 33)
high-speed steels (HSS): Tool steel that
has red hardness and a high resistance to
abrasion. Used in some cutting tools. (Ch. 28)
honeycomb sandwich panels: A material
made by bonding a honeycomb panel between
two fl at panels. Honeycomb sandwich panels
have a very high strength-to-weight ratio and
rigidity-to-weight ratio. (Ch. 28)
horizontal band saw: Frequently referred to
as a cutoff machine, it is a tool with a long,
continuous blade that moves in only one
direction. Cutting is continuous, and the
blade can run at very high speeds because it
rapidly dissipates the cutting heat. (Ch. 11)
horizontal machining center (HMC): A
machining center with a spindle oriented
horizontally. (Ch. 22)
horizontal milling machine: A category of
milling machine where the cutter is fi tted
onto an arbor mounted in the machine on
an axis parallel with the worktable. Multiple
cutters may be mounted on the arbor for
some operations. (Ch. 18)
hot rolled steel: Steel that has been rolled to
fi nished size while hot. Hot rolled steel is
identifi able by its black oxide surface scale.
(Ch. 28)
hydrodynamic machining (HDM): A
machining process that uses a high-velocity,
high-pressure stream of water to cut through
materials. Also called water jet cutting. (Ch. 32)
I
impact machining: A machining process that
removes metal by using ultrasonics and a
special tool to force abrasives against the work.
Also known as “slurry machining.” (Ch. 32)