Thanks to some great suggestions on a previous thread, I am using a
mitre saw to cut small (3 inch x 3/8 inch) aluminum bar, with
encouraging results. My follow up pertains to surface quality - in
general, mine is so far very poor.

The saw is spewing out what appear to be nice chips and the carbide
blade is brand new. The saw is fixed at about 5500 RPM, it is a 210mm
blade with 24 teeth. The surface finish looks as if it is splattered
with little globlets of aluminum. On some cuts, it almost looks like
there is a beautiful clean cut underneath, leading me to believe that
the cut is locally producing a good bit of heat which is welding some
of the cut material back onto the surface. Interestingly, the slower
I try to feed, the worse the problem seems to be.

Preliminary research indicates that RPMs, feed rate and lubrication
are all factors in surface quality. With this saw, anyway, I cannot
change the RPMs. Feed rate suggest faster is better. Lube helps a
bit, as is evidence by the times I take a very small amount off the
end (a couple hundreths) and am able to smear lube on the work as
opposed to when I cut off a piece in the middle, in which cases I have
to pre-load each tooth with a bit of grease, or plunge in dry. I am
guessing that the 5500 RPM is the culprit, and that it may end up that
this saw is not an appropriate tool for what I want to do.

Any advice, intuitions or experience that anyone cares to share?
Thanks in advance.

For the Miter saw, use a triple chip grind blade, not an alternate top
bevel as most "home centers" sell. You may be able to find a triple
chip blade there but it will probably be labeled for laminate or
similar. A slight reverse rake (2-5 degrees) on the teeth can help
also. This give you more control over your cut and pressures as it does
not dig in. There are special blades for this but if you aint doing it
all day, a triple chip with a 5 degree negative rake will get you
through (I use a systi-matic brand blade at home, sold through tool town
in the Seattle area) Works great on many plastic materials too by the way.

And you are right...keep the heat out and the feed as fast as you can
(and that can get scary on a hand held miter saw). For burless aluminum
tubing cutting, we run the saws at VERY high RPMS and they need to
plunge through the material quickly. The set up and clamping are very
rigid so we can feed that quickly.

Koz

ss wrote:

Thanks to some great suggestions on a previous thread, I am using a
mitre saw to cut small (3 inch x 3/8 inch) aluminum bar, with
encouraging results. My follow up pertains to surface quality - in
general, mine is so far very poor.

The saw is spewing out what appear to be nice chips and the carbide
blade is brand new. The saw is fixed at about 5500 RPM, it is a 210mm
blade with 24 teeth. The surface finish looks as if it is splattered
with little globlets of aluminum. On some cuts, it almost looks like
there is a beautiful clean cut underneath, leading me to believe that
the cut is locally producing a good bit of heat which is welding some
of the cut material back onto the surface. Interestingly, the slower
I try to feed, the worse the problem seems to be.

Preliminary research indicates that RPMs, feed rate and lubrication
are all factors in surface quality. With this saw, anyway, I cannot
change the RPMs. Feed rate suggest faster is better. Lube helps a
bit, as is evidence by the times I take a very small amount off the
end (a couple hundreths) and am able to smear lube on the work as
opposed to when I cut off a piece in the middle, in which cases I have
to pre-load each tooth with a bit of grease, or plunge in dry. I am
guessing that the 5500 RPM is the culprit, and that it may end up that
this saw is not an appropriate tool for what I want to do.

Any advice, intuitions or experience that anyone cares to share?
Thanks in advance.