Process for producing a rotary drilling bit

Abstract

A rotary drill bit for drilling wells in earth formations is produced by a casting technique using a plastic foam, combustible casting form. The bit includes a tapered drill body having a plurality of passageways therein which form jets for introducing liquid between the earth and a plurality of selectively arranged, cutting members extending outwardly from the drill body. The combustible form is molded in a shape substantially identical to that of the drill body. The cutting members are mounted on the form in the selective arrangement thereof, and the assembly of the form and cutting members are then coated with a mold material to form a mold body. A cavity is created in the form for receiving a molding mandrel which defines the longitudinal passageway of the completed bit. Molding pins are introduced through the mold body into the mandrel to precisely hold the mandrel relative to the mold body. The cutting members are precisely held by the mold body after the form is removed by combustion. Molten steel is introduced into the mold cavity, between the mold body and the mandrel to form the drill body. The mold body and mandrel are then removed from the completed bit by chemical treatment. The cutting members include a cobalt and/or nickel binder and are coated with a special substance to form a barrier between the drill body and the cutting members thereby to prevent adverse chemical reaction between the molten steel and the cobalt and/or nickel of the cutting members.