ENERGY
SAVINGS
Because cold drawn bars are strengthened by drawing process,
they are sometimes used by design engineers to gain strength
in parts without expensive heat treating. This, added to their
easier machinability, means energy savings.
SIZE ACCURACY
The close tolerances to which cold finished steel bars are
produced permit much smoother working collets. Adjustments
need not be made for extreme under - and over-size variations.
These same accuracies, together with
the smooth surface finish of a cold finished bar may reduce
the need for all-over machining.
FINISH
A cold finished bar is bright and smooth and has a metallic
luster. The surface does not need to be machined for the
sake of accuracy or appearance. The finest accuracy and
appearance are, of course, found in the ground and polished
bars.
STRAIGHTNESS
A cold finished steel bar is straight. It feeds out easily
in machining and works efficiently in the reels. Higher
revolutions pre minute are practicable because of less machine
vibration with cold finished steel.
MECHANICAL PROPERTIES
Cold drawing is a cold working operation and, as such, increases
both the tensile and yield strengths of steel. The yield
strength is usually about doubled. Ductility is reduced
somewhat while hardness is increased. It should be kept
in mind that the center of a cold drawn bar, as a general
rule, is cold worked to essentially the same degree as are
the zones nearer the surface and consequently, these properties
are changed the same amount through the bar.
Newer speciality steels included in this
book provide strengths from well over 100,000 psi to above
150,000 psi tensile in-the-bar and require NO HEAT TREATMENT.
These steel bars, developed exclusively by Niagara LaSalle,
are uniform and machinable.
TRUE TO SHAPE
Cold finished steel bars are true to shape. They are drawn
through precision dies which effectively control the shape
to be produced, i.e., round, hexagons, flats and squares.
BETTER PARTS
Seams and other defects are more readily discovered in cold
finished operations, thus lowering the percentage of parts
rejected after machining. With cold finished bars, parts
can be machined more accurately, which cuts down on extra
operations such as grinding on critical diameters. This,
in combination with the higher mechanical properties of
cold drawn bar stock, operates to provide higher quality
parts.
MACHINABILITY
The size accuracy, finish, straightness and concentricity
of cold finished steel bars are important in machining -
especially to the operation of automatic screw machines.
Cold drawn bars are produced from Special Bar Quality of
Alloy Bar Quality hot rolled bars. Internal soundness is
thus being checked directly at the producing mill. Cold
drawing, then, improves the inherent machinability of some
steels by 15 to 25% and makes chips easier to break and
dispose of, which can be important to high output NC and
CNC equipment. Cold drawn bars cut easier and cleaner.
The number of parts you produce per hour,
per machine, along with tool life, will normally increase
when you use bars in the cold drawn condition.
LESS SCREW MACHINE MAINTENANCE
Scale, which can collect and work its way into moving segments
of the machine and cause premature parts wear, has been
removed in cold finishing, there is less out-of-roundness
to cause strain on collets, pushers and fingers. Because
tolerances are more accurate, fewer machine adjustments
have to be made. These and other advantages all add up to
less labor, maintenance and cost.