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 11o and 12o are normally used on modern drill rigs. For low impact rock drills and softer rock formations, a narrow taper angle of 7o is used. A 7o angle can also be used if bit spinning is a problem when using 11o and 12o equipment.
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