Machining Fundamentals 620
servomechanism: In electrical discharge
machining, the drive unit used to accurately
control electrode movement and to maintain
the correct distance between the work and
the electrode as machining progresses.
(Ch. 31)
servo motor: A motor that can provide
feedback to a controlling mechanism; used
in higher-end CNC machines to drive axis
positions. (Ch. 22)
setover: The distance a lathe tailstock is offset
from the normal centerline of the machine. It
is a method of taper-turning. (Ch. 16)
side milling cutter: A type of milling
cutter with cutting edges located on the
circumference and on one or both sides of the
cutter. They are made in solid form or with
inserted teeth. (Ch. 18)
SI Metric system: The metric system of
weights and measures. (SI stands for the
French words Systeme International). Compare
with US Conventional system. (Ch. 4)
single-point cutting tool: A cutting tool with
one face and one cutting edge. (Ch. 14)
sintering: In the powder metallurgy process,
the operation in which the newly formed part
is heated in a controlled environment furnace
to give it strength. May also be used to refer
to the powder metallurgy process itself.
(Ch. 33)
skilled worker: A worker who has been
trained, often as an apprentice, to do more
complex tasks. (Ch. 2)
skills standards: Industry requirements for
skilled workers and the basis for industry-
recognized certifi cation obtained through
performance testing. (Ch. 1)
slitting: An operation in which a thin cutter
or rotary knife is used to cut sheet metal into
narrow strips. (Ch. 19)
slotting: Similar to slitting, except that the cut
is made only part way through the work. The
slot in a screw head is an example of slotting.
(Ch. 19)
small hole EDM drilling: A process that bores
small diameter holes in material by creating
an arc between a hollow, spinning electrode
and the workpiece. (Ch. 31)
smart tooling: Cutting tools and work-holding
devices that can be easily reconfi gured to
produce a variety of shapes and sizes within
a given part family. (Ch. 26)
spindle: On a lathe, the structure which
receives tools, attachments, or the workpiece,
revolves in heavy-duty bearings, and is
rotated by belts, gears, or a combination of
the two. (Ch. 14)
spontaneous combustion: Ignition by rapid
oxidation or burning of oil without an
external source of heat. (Ch. 3)
spotfacing: Machining a circular spot on the
surface of a part to furnish a fl at bearing
surface for mounting a bolthead or nuthead.
(Ch. 12)
spur gear: A wheel with teeth that run straight
across the gear face, perpendicular to the
sides. It is the most commonly used gear.
(Ch. 19)
square: A tool used to check 90° (square)
angles. It is also used for laying out lines that
must be at right angles to a given edge or
parallel to another edge. (Ch. 6)
statistical process control (SPC): A quality
control technique in which a percentage of
the products made during a production run
are tested. Statistical analysis of variations
detected in the products allows the
manufacturer to predict and correct problems
before they result in unacceptable products.
(Ch. 27)