US Patent 7314102 Percussion or hammer drill

A percussion or hammer drill is provided including a drill plate arranged in the head end of a drill shaft, extending completely across the diameter of the drill shaft and comprising an open front face. Wedge-shaped cutting edges and flanks form two main cutters on the front face, whereby a plane running through the drill axis forms a mid-plane-of both main cutters. The main cutters form a tip angle in the range of approximately 140° to 180° and are separated by a central point.