Abstract: An earth boring drill bit having roller cutters which are rotatably supported on journals by bushings. At least one of the bushings is formed by a plurality of bushing segments which are positioned about a circular bearing surface having thrust shoulders at each end thereof. The roller cutter elements are assembled about the bushing segments in heated condition, by press-fitting to establish a firmly seated relationship between the cutter and bushing segments upon cooling of the cutter. The rotary cutter is then secured to the bushing segments by means of a locking element to prevent inadvertent disassembly during drilling operations. End portions of the bushing segments engage hardened bearing inserts of cutter support legs to minimize wear during drilling operations. A circular sealing element positioned about the bushing segments establishes sealing engagement with the cutter support legs to prevent ingress of contaminants and egress of lubricant during drilling activity.

Abstract: A rotary earth boring drill is provided having a body structure with a plurality of depending cutter supporting legs having integral spindles extending transversely therefrom. Rotary cutter cone elements are supported by split bushings, roller bearings or a combination of the same, on appropriate bearing surfaces defined by the integral spindles. The bushings and cutter cones define mating tapered surfaces having an interference fit that secures the bushings and cutter cone in nonrotatable assembly. Circular locking elements are provided in locking grooves that are defined cooperatively by the bushings and cutter cones. End portions of the bushings extend axially beyond a planar surface defining one extremity of the cutter cone and establishes rotatable sealing engagement with an opposed planar surface defined by the depending leg structure of the bit. This rotatable seal prevents drill cuttings, dust and other debris from entering the bearing support of the cutter cone.