Patent ID: 8814483
Filing Date: 2014-08-26
Classification: B23B,Y10T

Abstract:
1. A twist drill having an axis of rotation A defining a forward to rear direction, the twist drill comprising a cutting portion and a drill body, the cutting portion comprising: a chisel edge; at least two flutes extending longitudinally to the drill body, each flute comprising a rake surface and a gash extending away from the chisel edge; at least two cutting segments, each cutting segment comprising: a main cutting edge which comprises a first cutting edge extending away from the chisel edge, a second cutting edge connected to the first cutting edge and a chamfer cutting edge connected to the second cutting edge; a segment relief surface; and a chamfer relief surface; the gash and the segment relief surface meet at the first cutting edge; the rake surface and the segment relief surface meet at the second cutting edge; the rake surface and the chamfer relief surface meet at the chamfer cutting edge; the first and second cutting edges are curved and the chamfer edge is straight; and the first and second cutting edges are concavely curved in the same side view.