| 摘要 |
A drill bit includes a shank, a transition portion, and a body portion defining a plurality of axially stacked, progressively sized steps. The steps include a first step and a terminal step coupled to the transition portion. The first step defines two tip flutes each disposed at a tip flute angle. The body portion defines two body flutes each extending from the first step to the transition portion and disposed at a body flute angle different from the tip flute angle. The drill bit includes a bit tip disposed at the distal end of the body portion and having a chisel edge, a first chisel surface on one side of the chisel edge, and a second chisel surface on an opposite side of the chisel edge. The first chisel surface defines a first relief angle. The second chisel surface defines a second relief angle different from the first relief angle. |
