Exact step drill bits with spiral flute tiain exact 07021 ideal for burr free drilling and reaming of sheet metal pipes and profiles and manufactured with tialn titanium aluminium nitride coating optimum for stainless steel machining surface hardness approx 3000 hv also features chamfering deburring zone drilling and deburring in one work step exact 07021 step drill with spiral flute tiain bore diameter 4 12mm