Tapered drill rod

Different rock formations and rock drills require different taper angles. When drilling with high impact hydraulic rock drills in medium-hard to hard and abrasive rock formations, a wide taper angle is normally used. Taper angles of 11 and 12-degrees are normally used on modern drill rigs. For low impact rock drills and softer rock formations, a narrow taper angle of 7 degrees is used. A 7 degree angle can also be used if bit spinning is a problem when using 11 and 12 degree equipment. In addition, a 4.46 degree angle is ideal for soft rock when you're using pneumatic or hydraulic drill rigs to prevent bits from spinning or becoming detached.