Method of drill bit manufacture

Abstract

A method is disclosed for the manufacture of a drill bit having a hollow tubular body, or drill bit components, with an exterior tungsten carbide coated surface, and with cutting elements positioned in the cutting surfaces thereof. The drill bit body, or a bit component, such as a cutting blade, is formed by casting in a mold providing the precise dimensions required in the finished bit. The mold is packed or coated over selected portions of the inner surface with particles of sintered tungsten carbide or similar sintered refractory hard metal. The mold has a plurality of soft iron or steel plugs extending from the walls thereof which are of the same diameter as the cutting inserts or passages into the bit body or bit component. A steel alloy, or cast iron, or nodular cast iron, is melted and poured into the mold. The temperature of the molten steel is sufficient to desinter the sintered tungsten carbide particles. The finished casting has the shape of the drill bit body, or bit component, with an exterior surface layer or tungsten carbide. The plugs are then drilled out and the cutting inserts and wear pads inserted in place. The coating extends for a substantial depth, is metallurgically bonded to the steel bit body, or bit component, and protects against wear during drilling for long periods of time.