calgon writes:

What should I get to make straight 90 degree or 45 degree cuts of
aluminum tube, sheet, etc? My arm is tired of hacksawing and my cuts are
never straight anyway.

Harbor Freight has a portable bandsaw about $80 (look for sales).
At least your arm won't tire.

Or you can get a Harbor Freight 4x6 bandsaw. That's $199 as of today's price.

93762-1VGA

Or as others told you, a table saw.