When I cut aluminum bar or t-slot extrusion on my bandsaw I am not happy with how "square" this edge is. I don't have a milling machine at home, and I have been told grinding aluminum is a very bad idea.
I used to build structures using the 80/20 aluminum extrusions , I used a mitre saw with a good aluminum cutting blade lubricated with stick wax (or any good cutting fluid). Makes beautiful square cuts with minimal burring. Be careful applying the stick wax to the rotating blade, otherwise your mitre saw will become a finger removing device by default :-(