An earth boring bit having an improved two piece bearing construction using an internally tapered and threaded, cantilevered bearing lug extending obliquely inwardly and downwardly from a leg carried by the body of the bit. An internally tapered and threaded bearing sleeve is made up on the lug, and includes a mouth that engages a shoulder on a base region of the bearing lug. The mouth of the sleeve has a minimum radial thickness such that the sleeve may be made up to a selected minimum torque. The bearing sleeve has a length greater than that of the treaded portion to define a thick walled inner end region to receive a resilient retainer ring in a groove that provides a minimum section over the threads on the interior of the sleeve. The sleeve is boronized to achieve wear resistance in a manner that does not substantially reduce strength.

A method for the remanufacture and reconditioning of rock drill bits of the type which include rolling cone cutters (12) includes the steps of separating the bit leg extensions (18), journals and cone cutters (12) from the bit body along a line perpendicular to the center of rotation of the bit body, salvaging usable cutter teeth (28), forming new leg, journal and cone assemblies and attaching the new assemblies to the salvaged bit body, which has been suitably machined ot accept the new assemblies. An alternate method includes removing separately each leg (18), journal and cone cutter (12) from the bit body in a manner which forms a curved saddle bore in the bit body, forming a new leg, journal and cone assembly including a mating surface corresponding the the configuration of the saddle bore and attaching each new assembly to the bit body at a saddle bore. A method of original manufacture for a rock drill bit is also disclosed wherein a one piece, unitary bit body is formed and the desired number of leg, journal and cone assemblies attached to the bit body according to one of the methods employed in the reconditioning process.

An earth boring bit having an improved two piece bearing construction using an internally tapered and threaded, cantilevered bearing lug extending obliquely inwardly and downwardly from a leg carried by the body of the bit. An internally tapered and threaded bearing sleeve is made up on the lug, and includes a mouth that engages a shoulder on a base region of the bearing lug. The mouth of the sleeve has a minimum radial thickness such that the sleeve may be made up to a selected minimum torque. The bearing sleeve has a length greater than that of the treaded portion to define a thick walled inner end region to receive a resilient retainer ring in a groove that provides a minimum section over the threads on the interior of the sleeve. The sleeve is boronized to achieve wear resistance in a manner that does not substantially reduce strength.

A rock bit having a body (1) integrally made with three legs (2), three bearing pins (3) implanted into the legs (2) and extending obliquely centripetally to the center line of the body (1), and three cone cutters (7) supported by the journals (6) thereof. The journal (6) of the bearing pin (3) has a shape of spherical segment with one base having a height larger than the radius, and a locking member (10) is provided to retain the cone cutter (7) in place. An appropriate conical shape of a though hole (5) in the leg (2) provided to insert the bearing pin (3) eliminates the need for block fabrication of the body (1).

An improved cutter retainer ring for a rock bit, the ring having a curved exterior portion and a truncated interior surface to minimize the stress during assembly.

An improved cutter retainer ring for a rock bit, the ring having a curved exterior portion and a truncated interior surface to minimize the stress during assembly.

The cutting edge of a bit of a rotary drill comprises an agglomerate of natural or synthetic diamond mounted at the free end of a shank freely rotatable in a socket in the body. Preferably the agglomerate and the free end of the shank are cold swaged together and preferably a resilient spring is Interposed about the shank between the body and the free end.

A method of assembling sections of an earth boring bit for welding has features to assure precise bit geometry. The method includes a step of providing a hole (41) in each bit section at the centerline (35) of the 120 degree faces on the interiors of the sections. A triad (45) is constructed for use in assembly and consists of three pins (47) joined together on one end, each having an axis 120 degrees apart from the other axes of the pins. The triad (45) is positioned in the holes in the 120 degree faces when the three sections of the bit are brought together. The shank ends of the sections have holes (29) for receiving dowels located in the welding fixture. Once the sections are positioned and pinned against movement at the shank ends and at the triad, the sections are clamped, then welded.