| 摘要 |
A series of bits (600, 680, 690, 710, 720, 780, 800, 820, 860, 920) are illustrated which can be used with a boring machine to drill a borehole underground with enhanced directional control. As an illustration, one drill bit (600) is formed of a body portion having a hexagonal cross-section where the bit attaches to the drill string which defines six parallel surfaces (610-620) with parallel cutting edges (622-632) defined at the intersection of each of the parallel surfaces. Angled surfaces (634, 636, 638) extend from intermediate the ends of the bit to the forward end. As the bit rotates, a cylindrical borehole is formed. When the bit is stopped to change the direction of drilling, a relief area exists between the parallel surfaces and the wall of the borehole and between the angled surfaces and the wall of the borehole to more easily deflect the bit to begin drilling in a new direction.
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