Hi Philip,
I made a jig and use a composite metal cutting blade in a skil saw. A tile saw also works well especially if you've got a wet saw to keep the dust down. A hack saw with a bi-metal fine tooth (32 tpi or higher) blade will also do a nice job but you should wrap the tube with masking tape at the cut line to keep it from splintering if you go this route.
Whatever you do, do not do it inside, do not breathe in the dust, and try very hard to keep the dust from grinding into your skin.