| 摘要 |
A drill bit for drilling subterranean formations includes a device to provide a "universal" effect between the shank and crown for self alignment of the crown with the bore hole in the formation. The bit is suitable for down-hole assemblies configured for straight drilling, directional drilling and navigational drilling. The device can be incorporated into both drag bits and roller-type "rock" bits. Preferred embodiments include a flexible sub connecting the crown to the shank portion and having reduced stiffness relative to the drill string. Alternatively, a spherical universal joint or trunnion type universal is used. Replaceable lugs increase durability and reliability of the universal. The device equalizes the loads on cutters while reducing wear, average loads, and impact loads on cutters. Bore hole diameter and chatter of the bit in the bore hole are reduced, promoting maximum efficiency and rate of penetration as wobble and precession are minimized.
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