... different taper angles. When drilling with high impact hydraulic rock drills in medium-hard to hard and abrasive ... for soft rock when you're using pneumatic or hydraulic drill rigs - to prevent bits from spinning or becoming ... (mm):29,30,31,32,33,34,35,36,37,38,39,40,41 Integral Drill Steel is used ... diameter from 30mm to 41mm usually. Regarding Integral drill steels,the quality of a steel material and a ...