Twist drill with negative axial rake transition between the lip and the secondary cutting edge

摘要

A drill for making a hole within a workpiece has a body extending along a longitudinal axis, at least one flute extending along the body, and a drill point extending from the end of the body. The drill point has a periphery and is comprised of a chisel edge, a primary cutting edge extending inwardly from the periphery, a secondary cutting edge extending outwardly from the chisel edge, and a tertiary cutting edge connecting the primary cutting edge with the secondary cutting edge, wherein the tertiary cutting edge has a negative axial rake angle. A method for producing such a drill point is also disclosed wherein in one grinding pass a gash forms the axial rake angle of the secondary cutting edge, and in a separate grinding pass a portion of the secondary cutting edge is removed to produce a tertiary cutting edge having an axial rake angle that is negative.