Abstract: The present invention relates to a drill bit incorporating one or more rotary cutters. The rotary cutters are supported for rotation by a bearing assembly including ball bearings running in races in the rotary cutter and drill bit body. The bearing assembly further includes an annular bushing. A sealing assembly including an O-ring seal is provided to seal lubricant within the bearing assembly and prevent external contaminants from entering the bearing assembly. A corrosive environment has been found to increase the occurrence of stress fractures in the areas above the juncture of cutter supporting structure and the bit body. It has been found that a sacrificial anode partitioned about the surfaces of the juncture renders the surfaces cathodic and resist stress fracture.

Abstract: The present invention relates to a drill bit (10) incorporating one or more rotary cutters (14). The rotary cutters (14) are supported for rotation by a bearing assembly including ball bearings (28) running in races (24, 26) in the rotary cutter and drill bit body (20). The bearing assembly further includes an annular bushing (34). A sealing assembly (36) including an O-ring seal (38) is provided to seal lubricant within the bearing assembly and prevent external contaminants from entering the bearing assembly. Corrosion has been found to destroy the seal surfaces (42, 44) against which the O-ring seal acts (38). It has been found that plating the sealing surfaces with a material passive to the electrochemical system or higher in the electromotive series than the material forming the sealing surfaces reduces corrosion. Alternatively, a sacrificial anode (68) is provided about the sealing surfaces to render the surfaces cathodic and resist corrosion.