Takes a nice sharp "tool" to cut aluminum smoothly. The more worn the cutting edge, the more chatter you likely get, even with steel frames at some point.
I had my UG P01 apart last night. I noticed burrs sticking (inside) out from the edge of some of the holes where the tool used to cut didn't cleanly cut, it just pushed aluminum out of it's way as it passed by. Maybe I should completely tear it apart and smooth out all those rough edges (some day when I'm looking for something to do). No one would be able to see it, but it would make me feel better.