Drill and surface insensitive starting drill for difficult materials and deep holes

摘要

A fluteless pyramid point drill for spotting holes for drills having an included angle from 90-160°. The preferred tool is double ended. Another embodiment features the pyramid point on the back end of a penetrating drill. An enhanced pyramid point geometry enables construction from technical ceramics. These embodiments included a notched pyramid, a dual pyramid, a beveled pyramid, and an eccentric pyramid. Another embodiment utilizes a grooved-body hollow pyramid for reaming holes. Geometries for a single sided penetrating drill for drilling hardened materials include a limited flute with a flute depth of ⅓ the drill diameter. Point angle embodiments include a 0-20° primary cutting edge and a steeper relief angle with a negative rake along the edge, a radial edge and steep relief angle with a negative rake along this edge. Additionally a pyramid point may be superimposed on the dual point angle for superior centering guidance.