| 摘要 |
<p>A drill bit comprises a shank defining a longitudinal axis. Three ribs extend in a curve about the longitudinal axis. The ribs include side edges extending for a first portion at a first angle relative to the longitudinal axis and for a second portion at a second angle relative to the longitudinal axis. A lead screw extends along the longitudinal axis and has threads extending at a thread angle. A cutting edge is formed along the edge of each of the ribs. The cutting edge has a bevel angle where the thread angle is less than the bevel angle.</p> |
