Abstract: A rolling cutter drill bit has at least one roller cutter mounted on a cantilevered bearing shaft with a sealed bearing and lubrication system, lubricant pressure balancing means, lubricant pressure relief means, and a volume compensating rigid face seal assembly axially movable through an operating range. The face seal assembly comprises two cooperating face seal rings, one ring mounted on the bearing shaft and the other ring mounted in the cutter; a first energizer for the seal ring mounted on the bearing shaft, having a stiffness K1; and a second energizer for the seal ring mounted in the cutter, having a stiffness K2. In order to minimize the variation in the sealing face force as the assembly moves through its operating range, the stiffness K2 is less than half, and preferably less than 0.2, of the stiffness K1.

Abstract: A method of manufacturing a rolling cutter drill bit comprising a bit body which carries cutter assemblies each of which includes a cutter journal on the bit body, a cutter rotatably mounted on the journal, and a threaded retention ring screwed onto the cutter to retain the cutter on the journal while permitting a limited degree of axial displacement of the cutter relative to the journal. The method comprises the steps of predetermining a desired magnitude of maximum permitted axial displacement between the cutter and the journal, and then employing components for the cutter assembly which are so dimensioned as to provide, when assembled to form the cutter assembly, a maximum permitted axial displacement which is not greater than the predetermined magnitude. The appropriately dimensioned components may be specifically manufactured to the required size, or may be selected from a stock of components of differing sizes.