Jun 01, 2013· For semi finishing, we will run a ¾inch finishing ball end mill as show in Figure 4. The process is a "Z" level semi finish pass at 6,000 rpm, .024" IPR, which is 144 ipm with a .03" step down. We can semi finish the complete cavity to within .015 inch of finish. This will eliminate any leftover material from the highfeed roughing mill.