Drill, especially rock drill, has free surface that is concave or extends inwards into cutting disc away from flat surface; free surface can be polygonal or ellipsoidal

摘要

The drill has an insertion end and a drill head with at least one cutting disc (10) on the leading end with at least one cutting edge and a cutting surface (12) leading the cutting edge in the direction of rotation and a free surface (14) behind the cutting edge. The free surface is concave or extends inwards into the disc away from a flat surface over at least some of the surface. Alternatively, the free surface can be polygonal or ellipsoidal.