run graph (Figure 5) shows that the
periods of “stalling” at half speed
were, in fact, drawing over 50A and
with peaks well over 80A. However,
once the blade had settled down, it
cruised at about 25A and at about
5,000 RPM.
The third run with the Start
Mode set at “very soft” (Figure 6)
and Timing Mode at “low” gave a
smooth and uneventful run up to
full speed (Figure 7) with peak
current of about 70A, and again
cruising at about 25A and 5,000
RPM. By taking a closer look at the
graph (Figure 8), it shows that the
blade was taking about four
seconds to reach full RPM.
So, You Want to Cut
Metal on Your Table Saw?
● by Kevin M. Berry
Like many bot builders, I started out as a woodworker. So, I have
a shop full of woodworking tools
and, now, a serious bot building
jones. Some of my woodworking
tools work great on metal, like a
hand drill, drill press, vice, and
screwdrivers. Of course, I had to
buy a drill index with metal bits,
since brad points don’t do so well
on steel. I learned a lot about how
much sharper metal is than wood
when a bit binds up in a hole, and
the workpiece does that spinny
plate of death number. So, clamping
isn’t just for glue-ups anymore.
My real learning came when
faced with sheets of metal to cut,
and no easy access to a shear, arc
jet cutter, waterjet, etc. Having a
table saw, I thought “Why not?”
Thus begins the journey to this short
article.
Safety note: I’m a fanatic
about doing things right. Face
shield, all guards intact, fences,
miter gauges, you name it. You
should be also!
First, I tried aluminum which is
every new bot builder’s friend. I
started off cutting 1/8” sheet using
my plywood thin-kerf blade. I
figured tiny teeth, looks like a hack
saw, right? Well, it actually cut
pretty good, using a slow feed.
Pretty soon, however, the teeth sure
clogged up.
32 SERVO 11.2011
