[garyklein]

Miter saws intended for carpentry are intended for cutting longer pieces of relatively soft, solid material.

This presents challenges when we use them to cut aluminum shapes.

If we are cutting a heavy block or bar of aluminum, the challenge is that the block and blade are heating up and the aluminum begins to weld to the blade teeth. This can be addressed with interrupted cuts and lots of coolant / lubricant on the blade. I typically just use a squirt of cutting oil on the side of the blade between cuts.

The length is the next problem. Most miter saws do not support the cut material very close to the blade. This is a problem with thin wall aluminum shapes and shorter pieces. The easy fix for this is to add support to the back of the fence such as a large aluminum angle plate on each side of the blade adjusted for minimum clearance or zero kerf. This will support the material close to the blade and reduce the grabbing tendency.

The next issue is chatter and rigidity of the material in the cut. If you have a piece of the shape that can flex into the blade during the cut, it will and the material will tear and perhaps carbide teeth will be lost. The aluminum has to be solidly supported. This is a special problem with very thin walls.

I recommend clamps be used to secure the material whenever possible. The generally supplied clamps are OK, except they are usually too far away from the blade. If your added back support is made longer than the original saw's back fence, then you can use a scrap piece of wood to help clamp and support shorter parts in the saw with a spacer block on the outside, similar to toe clamps used on a mill.

I find my blades last a lot longer with frequent cutting oil application. I have also used beeswax successfully. Just rub the block on the sides of the blade teeth before cutting. It is a little cleaner.