ANALYSIS OF THE GEOMETRY OF THE PERIPHERY OF THE FLANK FACE OF TWIST DRILLS GROUND WITH CYLINDRICAL AND CONICAL FORMS

As part of a larger investigation into the performance of double margin drills [1,2] it was observed that, as well as the expected wear on both the primary and secondary cutting lips, the flank face of the drill was also worn. Since drill flank face wear is normally associated with either an insufficiently positive or even a negative clearance angle, it was necessary to examine the geometry of the periphery of the flank face in order that drills could be manufactured with the angle of disposition of the second margin relative to the first such that a positive value of the circumferential clearance angle is always maintained. This paper contains that geometric analysis and describes the tests used to verify it. © 1979.