I've cut 1/4" alum sheet (4 ft cut) with a circular saw w/ a plain old carbide tipped wood blade! I asked one of the metal shop techs at my school and this is what he suggested, i thought he was crazy, but i trusted him. just set up a guide and went slowly with some cutting oil. I know it sounds crazy, but it worked really well. the carbide blade works really well as it chips the aluminum instead of grinding it, a lot less heat, it was slightly warm to the touch by the time I finished the cut. similar to any machining process with alum.--keep the heat down.