Abstract: A seal assembly particularly adapted for sealing rock bit bearings is disclosed. The seal comprises an O-ring made of a resilient material which swells substantially when effectively exposed to a lubricant used for lubricating the bearing. The O-ring seal is mounted into the rock bit in a relatively low state of compression or squeeze between the surfaces to be sealed. During operation of the bit, the O-ring seal swells due to exposure to the lubricant, and consequently compression or squeeze of the seal increases substantially. The novel seal assembly compensates for undesirable compression set and wear of the O-ring.

Abstract: Rolling cone rock bit seal and bearing hard surfaces having been made fully ready for assembly are first provided thin overlay coatings to enhance the resistance of the surfaces to both wear and corrosion. The coating is an engineering ceramic comprised of at least one nonmetallic element selected from a list consisting of C, O, and N, combined with at least one metallic element selected from a list consisting of Ti, Hf, Zr, Nb, Ta, W, B, Al, Co, and Cr. In a modified physical vapor deposition process, the selected coating will be developed at a temperature not to exceed 400.degree. Fahrenheit.

Abstract: A resilient O-ring shaft seal for use in a rotary rock bit is described wherein the degree of squeeze imposed upon the O-ring seal is increased in one or more discrete steps, occurring as drilling conditions or bearing deterioration cause rising temperatures to be imposed on the seal. The squeeze is increased in discrete steps through a thermally related shape change in one or more nitinol, or the like, back up rings positioned adjacent to the packing ring seal housed within a seal gland. The seal gland is formed between a rock bit journal and a rock cutter cone rotatably mounted to the journal.