IMPROVEMENTS IN OR RELATING TO ROTARY DRILL BITS

摘要

A rotary drill bit comprises a bit body (20) having a shank (21) for connection to a drill string and a passage (22) for supplying drilling fluid to the face of the bit, which carries a plurality of polycrystalline diamond preform cutting elements (26). The cutting elements (26) are mounted on a single radially extending blade (25) so that the bit is imbalanced and a resultant sideways force (27) is applied to the bit as it rotates during drilling. The gauge of the bit body is provided with a low friction bearing pad (28) which extends rearwardly of theblade (25) and transmits the resultant sideways force (27) to the sides of the bore hole. Since the bearing pad (28) is low friction, it slides around the surface of the formation and any tendency for bit whirl to be initiated is reduced.