Identification of the Causes of Drill Bit Bearing Wear.

The very harsh conditions of drill bit bearing operation in boreholes impose great demands on the strength of the materials. The fatigue life of drill bit bearings is governed mainly by the structural parameters, the method of thermochemical treatment, the quality of the drilling fluid, the rotational speed, and the axial weight thrust on the drill bit. In this paper an analysis of drill bit bearing wear is made on the basis of measurements of some of the bearing components after operation in a borehole. The possibility of increasing bit life by introducing structural and technological changes is discussed, in particular, the substitution of sliding bearings for roller bearings, improvements in bearing lubricant and drilling fluid quality, and sealing the bearing space to prevent contamination.