Abstract: An earth boring bit with sealed cutter bearings has a dual function pressure compensator for a lubricant reservoir. The earth boring bit has a bit body and downwardly extending legs which include bearing shafts that extend inward and downward for mounting rotary cutters, and seals are provided between the bearing shafts and the cutters. Lubricant flow passages extend from an interior cavity of the bit body, through the legs and the bearing shafts, and into the spaces located between the bearing shafts and the cutters. The pressure compensator extends between the cavity and the flow passages and has a movable piston. The compensator may be operated in a sealed lubricant system mode when the piston is locked in place or an air flow bypass mode by removing a locking member from securing the piston in place prior to securing the earth boring bit to a drill string.

Abstract: A sealed bearing rock bit has a plurality of legs with journals formed to extend inward and downward at the end of the legs. Each of the legs has a last machined surface located adjacent to the bases of the journals and into which a seal groove is formed which circumscribes the respective journal. Cutters are rotatably mounted to respective ones of the journals, with back faces of the cutters located adjacent to respective ones of the last machined surfaces. The back faces of the cutters have annular-shaped protrusions which extend from said back faces and protrude into the seal grooves beyond the last machined surfaces of said journals extending an annular-shaped seal surface which is engaged by a seal disposed in the seal groove, leaving more of the interface space between the journal and the cutter for larger roller bearings.

Abstract: An earth boring bit has rotary cutters with embedded tungsten carbide inserts and milled steel teeth. The teeth and the grooves are first milled into the cutters, with the grooves extending between bases of the teeth, parallel to the crests of the teeth. Hard facing is applied to surfaces of the teeth and the grooves, and then the cutters are heat treated. Insert sockets are drilled into the teeth, centrally disposed in crests of the teeth. The tungsten carbide inserts are secured in the insert sockets, aligned for forming cutting profiles with respective ones of the milled teeth. The cutters are preferably frustoconically shaped and used for a rotary cone rock bit, and the tungsten carbide inserts configured as chisel-shaped inserts having crests which are aligned parallel to the crests of the milled steel teeth.

Abstract: An earth boring bit has rotary cutters with embedded tungsten carbide inserts and milled steel teeth. The teeth and the grooves are first milled into the cutters, with the grooves extending between bases of the teeth, parallel to the crests of the teeth. Hard facing is applied to surfaces of the teeth and the grooves, and then the cutters are heat treated. Insert sockets are drilled into the teeth, centrally disposed in crests of the teeth. The tungsten carbide inserts are secured in the insert sockets, aligned for forming cutting profiles with respective ones of the milled teeth. The cutters are preferably frustoconically shaped and used for a rotary cone rock bit, and the tungsten carbide inserts configured as chisel-shaped inserts having crests which are aligned parallel to the crests of the milled steel teeth.

Abstract: An earth boring bit with sealed cutter bearings has lubricant flow passages which extend from an interior cavity of the bit body to spaces located between bearing shafts and rotary cutters. A lubricant compensator has an elongate body defined by a tube which has a first end disposed in one of the flow passages and a second end which extends into the interior cavity. A piston is initially disposed in the second end, biased to apply pressure to lubricant located in the flow passages. The first end has a section for receiving the piston when lubricant is expelled from within the tube. Apertures extend through a sidewall of the tube, spaced apart from the section in the first end and in fluid communication with the flow passages. The apertures, the flow passages, and the spaces located between bearing shafts and rotary cutters are sized for passing drilling fluid.

Abstract: An earth boring bit with sealed cutter bearings has lubricant flow passages which extend from an interior cavity of the bit body to spaces located between bearing shafts and rotary cutters. A lubricant compensator has an elongate body defined by a tube which has a first end disposed in one of the flow passages and a second end which extends into the interior cavity. A piston is initially disposed in the second end, biased to apply pressure to lubricant located in the flow passages. The first end has a section for receiving the piston when lubricant is expelled from within the tube. Apertures extend through a sidewall of the tube, spaced apart from the section in the first end and in fluid communication with the flow passages. The apertures, the flow passages, and the spaces located between bearing shafts and rotary cutters are sized for passing drilling fluid.