| 摘要 |
<p>An improved self-centering spade drill (14) having at least three cutting blades (44) extending radially outward from the center of the drill (14), the front edge (52) of the blade (44) constituting the cutting portion of the drill (14), the rear edge (50) of the blade (44) constituting the port end of the drill which are adapted to be received and supported by a drill holder (12).</p> |
