I'm sure David will get it figured. One thing I have learned is every machine acts different. You want .050 and get .051, or you ask for .018 and get .015.
Carbide tooling is the way to go if you have a lot of material to remove, but it gets expensive in a hurry. It needs a rigid set up as it is hard as ***k but it can be brittle and chip. HSS is tougher but you got to go slower.
Emery cloth is your friend.
What are the soft jaws for??
Hmm, I do have access to some aluminum. And a mill.