Mitre saw surface finish

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: