Machining hardened stock isn’t for the faint of heart, but many alert shops have figured out how. In fact, some are running steels up to Rc 60 four or five times faster—even in cavity work. Others have even found a way to mill the hard stuff on light-duty machines using conventional end milling,

Hard materials are less forgiving, so everything matters more when it comes to the milling process, also, tool life is a bigger factor in overall process economics. Minimizing stoppage time for indexing can often save more machining money than ramping up the feedrate,
We offers these tips for successful hard part milling.

1) Be sure the machine is rigid. Hard workpieces can exacerbate any looseness in the machine or fixturing.

2) Manage heat. Hard part milling will generate more of it. Spindles that are air cooled and designed to minimize heat flow back to the machine frame are preferred.

3) For cavity work, opt for high-end software with look-ahead capability. That plus careful programming can keep chip loads uniform in and out of corners. In any metal, you don’t want to have to slow down at each corner, yet you can’t afford transient chip loads able to snap off a tool. Be especially careful of it in hard materials.

4) Choose robustly designed cutter bodies with extremely secure seating and quick indexing capability. In inserts, look for geometries that reduce cutting forces and fine grained microstructures with improved shock and impact tolerance.