Look here:
Search for foiling
http://www.cnczone.com/forums/showpo...48&postcount=3
I use it all the time. Usually 0.2mm all round, and the last cut just skips the first and second corner by 0.1mm and goes below by 0.2mm the rest of the way. Break it out with your fingers. Be careful that Z moves don't leave marks. Usually better not to move z in the last pass and go around the foiled corners over a thicker area you leave for support.
Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.