| 摘要 |
<p>A twist drill includes a cutting portion and a drill body. The cutting portion has a chisel edge, a segment relief surface, a chamfer relief surface and at least two flutes extending longitudinally to the drill body. Each flute has a rake surface and a gash extending away from the chisel edge. The cutting portion further has at least two cutting segments, each cutting segment having a first curved cutting edge, a second curved cutting edge and a chamfer cutting edge.</p> |
