| 摘要 |
A drill bit consists of a bit body having a forward end and a slot in the forward end to hold a hardened cutting blade. The bit body has a table near the center of the blade to reduce the speed at which the drill bores into hard material. The blade has a central slot extending into the forward end thereof such that the slot defines inner side walls and a bridge extending between the inner side walls. The bridge has sloping sides the define a central cutting edge so as to cut particles of hard material accumulating in the slot. The inner side walls intersect the leading faces of the blade and form cutting edges which further cut particles loosened at the center of the cut. Also, relief flats relieve the concentration of forces at the ends of the primary cutting edges of the blade.
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