| 摘要 |
"Improvement 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 imbalance force to the bit as it rotates during drilling and the gauge of the bit body is provided with low friction bearing pads to transmit said resultant lateral force to the sides of the borehole. Each low friction bearing pad includes an outwardly facing cavity which is connected to the passage by a chocked conduit so that, in use, drilling fluid under pressure is delivered to the cavity , which thereby acts as a low friction hydrostatic bearing surface. |
