Improvements in or relating to preform cutting elements for rotary drill bits

摘要

A preform cutting element for a rotary drag-type drill bit comprises a front facing table (28) of superhard material having a front surface, a peripheral surface, a rear surface bonded to a substrate (29) of less hard material, and a cutting edge (35) formed by at least part of the junction between the front surface and the peripheral surface. The front surface of the facing table is formed with a chip-breaking formation which is located adjacent the cutting edge and is shaped to deflect transversely of the front surface of the facing table cuttings which, in use, are removed by the cutting edge from the formation being drilled. The chip-breaking formation comprises a projection (34) which upstands from the front surface of the facing table. <IMAGE>