1. GENERAL
from soft to spring tempered, with a hard edge only
the depth of the teeth. It is the most common of the
Bandsawing machines are unique compared to
carbon steel blades.
other machine tools in that they use a flexible
cutting tool. Tensioning the tool (saw blade) and
The softer back on this type of blade has the lowest
supporting it near the cutting zone (with saw
tensile strength of all blades. This makes for the
guides) results in its becoming sufficiently rigid
lowest "beam strength", limiting the amount of
to perform useful work.
cutting force which can be applied. (Beam strength
is the deflection of the blade body between the saw
Most machine tools feed the cutting tool on the
guides as it contacts the work piece and a cutting
basis of inches per revolution. Band saws generally
force develops. ) Blade tensioning is also the lowest
feed the cutting tool based on pounds of cutting
of all blades as a result of the low tensile strength
force. This allows the tool to cut at its own rate
of the blade back.
in relation to inches per revolution.
When the proper cutting feed force is applied to the
2.3 HARD BACK BLADES
blade, it will cut at maximum efficiency and still
maintain good accuracy. This type of feed is
Hard back blades are the second type of carbon
necessary because most cutoff sawing involves
steel blade. This blade is completely heat treated,
ever-changing cross section areas. With this
edge and back, with the back as hard as possible
method the blade will not be over-fed as it enters
while still allowing it to flex around the drive
a larger cross section area. The cutting force will
wheels. The hard back improves the two limiting
be maintained but the forward progress of the blade
factors discussed in section 2.2, beam strength and
into the cut will slow, until it enters a smaller
tensile strength.
section. At this point it will progress faster through
the cut. This explains why THE BLADE CUTS
Because this blade is an improvement over the
AT ITS OWN RATE.
"soft back", it can be more highly tensioned with
a resulting improved beam strength. It can be fed
2. BLADE TYPES
into the work piece with. more cutting force. This
provides an increased cutting rate. However, the
Band saw blades are generally referred to by the
blade cannot travel any faster in lineal feet per min-
type of material from which they are made. "CAR-
ute without losing the heat treatment.
BON" blades are manufactured from high carbon
steel and "HIGH SPEED" blades are manufac-
tured from high speed steel. The "WELDED
2.4 ALLOY STEEL BLADES
EDGE" blade has a high speed steel strip welded
Alloy steel blades offer an improvement over car-
to an alloy blade back. "CARBIDE" blades have
bon steel blades. They can be operated at higher
carbide steel fused to the tooth tips.
lineal feet per minute speeds, and have greater
beam strength and tensioning strength. This
2.1 CARBON STEEL BLADES
results in increased cutting rates as we can operate
Carbon steel blades can be called the work horse
the blade at higher speeds and with greater cutting
of the industry, as they are very widely used. They
force.
perform well on steel sections, aluminum, plastics,
carbon and similar materials. The limiting factor
Some alloys that work-harden with cutting can be
is the cutting rate. As the cutting rate is increased
cut with alloy steel blades that cannot be cut with
the heat generated in the blade increases. Carbon
carbon steel blades. A very heavy cutting force
blades will easily reach a temperature that removes
must be used, and the alloy steel teeth have suffic-
the heat treatment of the steel, allowing the teeth
ient strength to cut without stripping.
to dull. They do, however, work very well on appli-
cations where high cutting rates are not required.
Alloy steel blades are also referred to as "interme-
On steel they are seldom run over 120 lineal feet per
diate" or "semi-high speed". Their performance
minute with coolant, and will cut materials up to
levels fall somewhere between carbon steel and high
250 Brinell hardness with good results.
speed steel blades. There is no standardization be-
tween manufacturers of these blades, and they vary
The two basic types of carbon steel blades are as
widely. Some approach the performance of high
follows:
speed steel blades while others are only slightly
improved over carbon steel blades.
2.2 CARBON STEEL BLADES WITH A HARD
EDGE AND A SOFT OR FLEXIBLE BACK
When using alloy steel blades we suggest working
closely with the blade manufacturer.
This blade is available with several types of backs,
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