SECONDARY CUTTING ELEMENT FOR DRILL BIT

摘要

A rotary drag bit comprises a bit body and a plurality of blades extending radially away from the bit body, each blade including a cutting assembly. Each cutting assembly has a plurality of primary cutters orientated in the direction of rotation of the drill bit for drilling or boring into a subterranean rock formation, and a plurality of secondary or brute cutters located behind the primary cutters in relation to the direction of rotation of the drag bit. The invention is concerned primarily with the secondary cutters, which comprise a layer of superabrasive material, such as PCD, PCBN or CVD diamond, bonded to a support substrate. The interface between the superabrasive layer and the substrate has a stepped region that provides the cutter with a skirt or hoop of superabrasive extending into the substrate. The secondary cutter is orientated in use to present a bearing surface to the rock formation and a secondary cutting edge in the direction of rotation of the rotary bit.