Abstract: A rolling cone cutter earth boring bit is provided with an improved bearing system including reduced clearance bearing surfaces and a space for lubricant. At least one cantilevered bearing pin extends from the arm of the bit. A rolling cone cutter is rotatably mounted on the bearing pin. The outer bearing surface of the bearing pin is provided by forming a recess in the load surface of the bearing pin and filling the recess with bearing material. The unloaded surface of the bearing pin is formed by eccentric machining. Reduced clearance is provided between the rolling cone cutter and the load surface of the bearing pin and increased clearance is provided between the rolling cone cutter and the unloaded surface. The clearance on the unloaded surface serves as a lubricant reservoir in close proximity to the load surface of the bearing pin.

Abstract: A rotary rock bit is constructed having rolling cutter members for forming a borehole in the earth. Each rolling cutter member includes an annular row of cutting elements for cutting portions of the borehole. The cutting elements comprise cutting teeth or cutting inserts. Varied pitches are provided between the inserts/teeth. The pitches between pairs of inserts/teeth are varied so that the pitches between no two pairs of inserts/teeth in a row or group are the same. Since no two pairs of inserts/teeth have the same pitch, the probability of tracking will be remote. This increases the rate at which the bit penetrates the formation and generally decreases the probability of insert/tooth breakage therein. The present invention reduces or eliminates tracking and stumbling encountered in prior art earth boring bits.