321 Stainless is nasty stuff to drill. I recently had an application to drill 321 SS that was hardened and annealed according to the supplier to RC 32-36 (340Bhn max)We were drilling 2mm (.0787") diameter holes 10mm (.393")deep. Running "Walter Titex" A1249XPL-2 HSCO coated (XPL is a very hard...