By Dale Petts
For years the band sawing operation was a bit of a tortoise, at least relative to other process- es in sheet metal, plate, and structural fabrication. Compared to other cutting operations—
be it with a laser, plasma torch, or turret punch
press—it took a long time for a saw to cut through
a workpiece of any substantial size.
But times have changed. Band saws now slice
through metal at an unprecedented rate. In the
past a bimetal blade cutting through a 10-inch-
diameter round bar of 316 stainless could take 23
minutes; now shops are accomplishing the same
in less than half the time. And for I, H, and other
structural beams, the cut time has shortened to the
point where the indexing time between cuts (
depending on the length of the beam, of course) can
be close to the actual cutting time (see Figure 1).
This trend not only makes band sawing more ef-
ficient, it also has made looking at the big picture
even more important. Factors like operational con-
sistency, material handling and indexing, blade life,
and cut quality also enter the equation. To that end,
here are five questions you can ask to help deter-
mine the total cost of your band sawing operation.
1. What are my cut times?
Being a mechanized process, band sawing doesn’t
require a lot of direct labor. What dominates are
the fixed costs—overhead, front-o;ce workers,
e;ectively all the expenses it takes for a factory to
keep its doors open. For example, if the fixed cost
or burden rate for your band saw is $100 an hour,
that’s $800 over one shift of work. What if that
band saw could cut twice as many pieces during a
shift? ;at would save $800 in the burden rate over
a given day, thanks to higher productivity. Getting
more out of your existing band saw may help you
avoid hiring more people or buying more equipment. To do this often involves taking a look at the
band saw blade.
Band sawing essentially is a machining process. It
cuts away at the metal and produces metal chips.
Any machinist will tell you that achieving a precision cut takes more than sharp edges. It also takes a
rigid machine, including a rigid toolholder.
;e tips of band saw blades have evolved to become precision cutting tools, but they sit on a less
than optimal “toolholder”: that is, the backing steel
of the band saw blade, typically a grade of carbon
spring steel. In a traditional operation, the blade
cuts along a single plane, one straight line across
the entire workpiece. ;is forces all teeth within
the cut kerf to engage the metal simultaneously.
;at’s roughly analogous to aggressive milling, or
“hogging out,” on a milling machine.
In recent years, though, machinists have discovered that removing a lot of material quickly and
producing a smooth finish requires a di;erent approach: high-speed machining. Instead of diving
into the workpiece with one long cut, the cutting
tool engages fewer cutting edges at once on each
pass. With few cutting edges engaged at once, it
takes less pressure per cutting-tool point to penetrate the metal. ;is allows the machine to mill
with less pressure but still remove more material in
To a certain extent this idea also can be applied to
band sawing, but not by simply reducing the feed
pressure. ;is would not only increase cut time,
but also prematurely wear your blade. Instead, it’s
about better tooth geometry, optimal pressure,
and reducing the number of teeth engaged in the
workpiece at a given moment.
To accomplish this, advancements have focused
on the shape of the blade back itself. Unlike a conventional blade back edge that is parallel with the
blade teeth, the back edge of certain newly developed blades are angled or tapered at specific
points. ;e degree, length, and shape of these tapers are dictated by the cutting application.
Consider two blades, one designed to handle
up to a maximum of 40-in.-wide material and another for cutting a maximum of 20-in.-wide material. ;ose two blades will require starkly di;erent size teeth, of course. ;e 40-in. piece generally
requires larger teeth (fewer teeth per inch, or TPI)
because it has to travel a long distance once inside
the cut, cutting and storing chips inside the gullet
between the teeth before they evacuate at the end
of the cut. Using a smaller tooth and finer pitch on
such a long cut requires proportionally higher cutting forces, and forces the teeth to rub along the
work, resisting penetration. ;is potentially causes
crooked cuts and shortens blade life.
Besides di;erences in teeth size and pitch pattern (which have become standard in the industry), there also can be di;erences in the tapers on
the back of the blade. It’s a subtle di;erence, but
that small change in the taper can make a big difference in the blade performance.
As the back edge of the blade travels, it presses
CUTTING AWAY AT
BAND SAWING COSTS
5 questions to ask that will
help improve your sawing operation
;is bimetal blade is designed specifically for cutting
bundles and structural material.