| 摘要 |
<p>A drill (20) having an elongated body (11) including a fluted land (12) and a shank (25). The fluted land (12) includes a plurality of radial grooves (47, 49, 51) of reduced material thickness formed therein to the depth of the flutes (27, 29, 31). The grooves (47-51) define discrete segments (53, 55, 57) of the drill (20). Each segment (53, 55, 57) has a facet (59, 61, 63) which has the relief of a drill tip (12) so that when the exposed drill tip (12) becomes dull, the segment (53) can be broken off at the notch exposing a successive, sharp drill tip. The drill (20) can have the cutting edges coated with an appropriate protective material such as TiN, titianium nitride, titanium carbide, titanium carbonitride or any other appropriate coating material to improve cutting and preserve the edge.</p> |
