... three types: Standard 2 flutes high speed drill bit, high speed 2 flutes short flute drill bit with cooled(3xd), 2 Flute High ... Speed Tungsten Carbide Drill Bit With Cooled(5xd).2.AlTiN coating, black, high aluminum coating, applicative to CNC milling machine processing general ... higher Co, the better wear-resistance.6.ZHY-600 series drill bit, grain size 0.4um, Co12%, HRC60, AlTiN coating, ...