Abstract: A sealed, pressure-equalizing lubrication system for a rotary rock bit is shown. The system includes a lubricant-filled container having an outlet and a portion of the container includes a flexible diaphragm. The container is mounted in a chamber in the journal axle portion of the bit, immediately adjacent and open to the sealed bearing cavity of the bit cutter, with the outlet disposed adjacent the cavity. A bleed hole is provided from the back face of the bit to the chamber adjacent the diaphragm causing the diaphragm to be responsive to the pressure of the external downhole fluid. The adjacency of the reservoir to the sealed bearing cavity permits the pressure of the lubricant adjacent the seal to be immediately responsive to the pressure of the downhole fluid at the diaphragm to prevent pressure differentials between the lubricant and the fluid at the seal.

Abstract: Structure for permanently retaining a rolling cutter on a journal pin of a rotary cutter earth boring bit is shown. The structure is defined by opposed, axially aligned, circumferential grooves formed in the mating bearing surfaces of the pin and the assembled cutter. The cutter groove is a single width throughout whereas the pin groove defines a double width for an arcuate extent thereof on its unloaded side. A split snap ring is compressed within the pin groove, with the ends of the ring axially overlapping in the double width portion so that the ring does not extend above the surface of the pin. Upon alignment of the grooves, during assembly of the cutter on the pin, the ring snaps into the cutter groove with the ends in abutting relationship and extends radially into the pin groove to retain the cutter on the pin.