Glossary of Technical Terms 621
steady rest: A support for long, thin
workpieces that keeps the work from
springing or bending away from the cutting
tool. The rest also reduces “chatter” when
long shafts are machined. Compare with
follower rest. (Ch. 15)
steel rule: A measuring tool, available in
at least three basic types of graduations:
fractional inch, decimal inch, and metric.
(Ch. 5)
stepper motor: A motor that moves in small
steps, or increments, and does not provide
feedback to the controlling mechanism.
(Ch. 22)
stereolithography: A rapid prototyping
technique that uses a computer-guided
low-power laser beam to harden a liquid
photocurable polymer plastic into the
programmed shape. (Ch. 26)
straddle milling: Using two or more milling
cutters to perform several milling operations
simultaneously. (Ch. 19)
straightedge: A precision tool for checking the
accuracy of fl at surfaces. (Ch. 6)
straightness: The measure of how closely an
element of a surface or axis is to a perfectly
straight line. (Ch. 4)
straight set: A two-tooth saw set in which
one tooth is angled to the side and the
other one straight, alternating continuously
along the length of the blade. Straight set is
recommended for materials like aluminum
and magnesium. (Ch. 21)
stress-relieving: Removing internal stresses
that have developed in parts that have been
cold worked, machined, or welded. Also
called process annealing. (Ch. 29)
subroutine: A set of commands that follows
a prescribed sequence again and again until
cancelled. Also called canned cycle. (Ch. 24)
surface gage: A scribing tool used to check
whether a part is parallel to a given surface.
(Ch. 6)
surface hardening: A heat treatment process
used to create a medium-hard surface on
high-carbon or alloy steel while leaving the
inner core of the metal unaffected. (Ch. 29)
surface plate: A cast iron or granite plate,
ground or lapped to a smooth fl at surface,
and used for precision layout and inspection.
(Ch. 6)
surface roughness standards: Documents
that detail how surfaces produced by
machining, grinding, casting, molding,
forging, or similar processes are to be
measured and communicated. (Ch. 30)
swing: Indicates the largest diameter that can
be turned over the ways. Along with the
length of the bed, determines the size of the
lathe. (Ch. 14)
Swiss-type turning center: A type of turning
center or lathe that can produce elaborate
detail in machined parts with a high degree
of precision and accuracy. (Ch. 22)
symmetry: A relationship that indicates equal
or balanced proportions on either side of a
central plane or datum. (Ch. 4)
T
tailstock: A movable lathe fi xture that mounts
on ways to support work between centers. It
can be fi tted with tools for drilling, reaming,
and threading. (Ch. 14)
taper: A piece that uniformly increases or
decreases in diameter to assume a wedge or
conical shape. (Ch. 16)
taper attachment: A guide attached to a lathe
and used to accurately cut internal and
external tapers. (Ch. 16)