Abstract: A rotary drill bit for use in drilling or coring holes in subsurface formations comprises a bit body having a shank for connection to a drill string, a plurality of cutting structures mounted at the surface of the bit body, and a passage in the bit body for supplying drilling fluid to the surface of the bit body for cooling and/or cleaning the cutting structures. The bit body is formed from steel, and each cutting structure comprises a cutting element, in the form of a unitary layer of thermally stable polycrystalline diamond material, brazed to a carrier received in a socket in the steel body of the bit.

Abstract: A rotary drill bit for use in drilling or coring deep holes in subsurface formations comprises a bit body having a leading face and a gauge region, cutting elements mounted at the leading face of the bit body, and a passage in the bit body communicating with nozzles in the leading face of the bit body for supplying drilling fluid to the face for cooling and cleaning the cutting elements. Certain of the cutting elements each comprise a preform cutting element having a superhard front cutting face providing a cutting edge, and others of the cutting elements each comprise particles of hard material embedded in a front layer of a less hard material to form a cutting layer having a cutting edge.

Abstract: A method of manufacturing a rotary drill bit of the kind comprising a bit body having a shank for connection to a drill string, a plurality of cutting structures mounted in sockets in the bit body, and a number of nozzles also mounted in sockets in the bit body and communicating with a passage for supplying drilling fluid to the face of the bit. The method includes the steps of forming at least part of the bit body from steel, forming the sockets in the bit body part, plugging each socket with a former which projects partly beyond the bit face, applying to the bit face a coating of a fusible hardfacing material, heating the coated bit body part so as to fuse the hardfacing material, cooling the bit body part to solidify the fused hardfacing material, and then removing the formers from the sockets.