... toughness4Special for drilling hard metal 1.The feature of high-speed drill bits:--the diameter of flute: 0.5-9.5 mm--the blade ... ,HRC 60 carbide drill bits are made from Kennametal material ,HRC 65 are made from Sandvik material Grade Recommend GradeHardness HRA ... .291-91.50.6um>3800Suit for processing Die Steel,aluminum alloy,stainless steel,cat iron ,copperKennametal 221091.50.5um>4300Suit for ...