These are good american made end mills. I found the error though. Thanks to all for the help. I took your advice of slowing the rpms and climb milling and a long ramp up and it did help, but I found the flexing was in the gantry itself (good call Graham). After a base plate replacement, both mills are performing well. The mini mill head still makes me take .005 at a pass at 10 ipm. Does roughing end mills speed up the process much? What other tooling have you mini mill guys used to speed up "hogging" large amounts of aluminum?