| 摘要 |
"Improvements in or relating to rotary drill bits" A rotary drill bit comprises a bit body having a shank for connection to a drill string and a passage for supplying drilling fluid to the face of the bit, which carries a plurality of polycrystalline diamond preform cutting elements In order to reduce bit whirl, the cutting elements are so disposed as to apply a resultant lateral force to the bit as it rotates during drilling, and the gauge of the bit body is provided with low friction bearing means to transmit said resultant force to the sides of the borehole. Each low friction bearing means includes a roller mounted on the bit body for rotation about an axis parallel to the axis of rotation of the bit, each roller being so disposed that its periphery bears on the formation as the bit rotates. |
