MICRO DRILL

摘要

A micro twist drill (11) having a pair of oppositely disposed flutes (13) which helically extend from the drill tip (22) along the body (15). The flutes (13) define a pair of oppositely disposed wings (17), each of which has a leading surface (45) (relative to the direction of rotation of the drill) which is undercut to provide a peripheral positive rake cutting edge which makes an angle (A) of from about 5 to about 30 to a radius of the drill body (15) which extends to the cutting edge. The drill (11) has a traverse cross section in which the leading surface (45) of each wing is provided with a curved channel (51) which trails a line between the cutting edges (47) of the two wings (17). The trailing surface (53) of each of the wings (17) defines a curve which substantially continuously recedes from the path of the cutting edge (47) to the point where it meets the leading surface (45) of the other wing (17).