Patent ID: 6056072
Filing Date: 2000-05-02
Classification: C10M,C10N,E21B

Abstract:
An earth boring drill bit of the type having a bearing pin extending from a head section of the drill bit for rotatably mounting a cutter thereon, the bearing pin having an external region which contacts an internal region of the cutter after assembly, a lubrication system in the body including a hydrostatic pressure compensator, a mechanical face seal assembly for retaining lubricant in the lubrication system and a bearing grease for lubricating the region of contact between the external region of the bearing pin and the internal region of the cutter, the grease comprising:a synthetic fluid base;a thickener system for synthetic fluid base which when added to the base forms a lubricating grease and imparts not only gel structure to the grease but also extreme pressure and antiwear properties;wherein the resulting lubricating grease is stable at downhole temperatures and pressures so as to be useful in bits drilling in hot subterranean formations;wherein the synthetic fluid base is a hydrogenated polyalphaolefin synthetic hydrocarbon oil having a viscosity of 10 to 100 centistokes at 100 degrees C., or a mixture of such oils.