Abstract: A novel form of drill bit is disclosed. The bit (30) comprises a bit body having a leading face (32) and gauge surface (44, 46). Cutting inserts (32, 34, 36) are set into the bit body, each cutting insert being in the form of a segment of a composite PCD (polycrystalline diamond) or PCBN (polycrystalline cubic boron nitride) composite. Thus each insert has a PCD or PCBN compact (40) carried by a carbide backing (42). The PCD or PCBN compact of each insert is exposed at the leading face or at the gauge surface to perform an axial cutting or gauge maintenance function during drilling.

Abstract: A rotatable crown for a rotary drill comprising a working end and an opposite end for engagement in a drill rod, stringer or adaptor coupling, the working end having a cutting face and a plurality of discrete, spaced, elongate cutting elements located in the cutting face, each cutting element:(1) being of square or rectangular cross-section;(2) presenting a cutting point which is defined by a corner of the element;(3) having a longitudinal axis which extends behind the cutting face; and(4) being made of thermally stable abrasive compact.The crown has particular application for the drilling of substrates having a compressive strength of at least 180 MPa such as Paarl granite, Norite Gabbro and Reef Quartzite.