Blade drill bit and method for its manufacture

摘要

A drill bit comprises a main body part 11 having a shank 13 for connection to a drill string, an end face, an internal passage 9 for supplying drilling fluid to the end face, a number of blades 15 extending from the end face outwardly and longitudinally of the central axis of rotation of the bit, and a number of cutters 16 mounted on each said blade. Each blade comprises a central metal core at least partly surrounded by solid infiltrated matrix material. A method of manufacturing such a drill bit includes the steps of providing a metal mandrel 17 having said shank and internal passage, and providing on the mandrel, so as to be supported by it, a number of blade cores 22 each having a portion extending outwardly and longitudinally of the central axis of the mandrel, casting infiltrated matrix material 23 around at least a part of each core 22 and around at least a part of the mandrel 17 to form the blades, and then removing portions of the cores 22 so as to detach each core from support by the mandrel 17 to leave within each blade a core 22 which is substantially wholly supported by the surrounding matrix material 23.