An earth boring bit is shown having a bit body and at least one cutter rotatably secured to the bit body. The cutter has a plurality of teeth formed integrally thereon and arranged in circumferential rows. Each of the teeth includes an outer end, an inner end, a pair of flanks and a crest which transversely connects the ends and flanks. During the manufacturing process, a temporary protective coating is applied at a region of the tooth root which comprises a sharp corner at the intersection of the flanks and ends in order to prevent a carburized case from forming in that region during subsequent carburization of the cutter. The cutter is then carburized, heat treated and mounted on a bit body.
A method is disclosed for applying hardfacing to a shirttail portion of a roller cone drill bit, including masking around the shirttail portion of the bit and operating a high pressure/high velocity oxygen fuel torch to apply the hardfacing to the shirttail portion.
A method for applying hardfacing to teeth on a drill bit is disclosed. The method includes applying the hardfacing to at least one of the teeth so as to have a thickness selected to correspond to a position about exterior surface of the tooth. In one embodiment, the hardfacing thickness is increased near the crest of the tooth, and is decreased near the root of the tooth on at least one flank of the tooth. In one embodiment, the thickness is selected by controlling the powder flow rate in a plasma transferred arc welding system. In another embodiment an angle subtended by flanks of the tooth is selected to provide increased strength to the tooth, and the hardfacing is applied to the tooth to cause exterior surfaces of the hardfacing corresponding to the flanks to subtend an angle selected to provide increased penetration of the tooth through earth formations while drilling.
The preferred embodiments are directed toward methods and apparatus for manufacturing components for earth-boring drill bits. In the preferred embodiments, a portion of the component is coated and the component is exposed to a carbon-rich environment at an elevated temperature. During this exposure, some portions of the component are not coated. The preferred embodiments further comprise coating the areas that were exposed to the carbon-rich environment and exposing the component to an elevated temperature in an environment with carbon present. In one embodiment, a drill leg is coated (with the exception of the journal pin) and then exposed to a carbon-rich environment at an elevated temperature. In this embodiment, the journal pin is then coated and the drill leg is exposed to an elevated temperature with a percentage of carbon that is less than the initial carbon-rich environment.
A method of dynamically balancing a hole enlargement system is disclosed. The method includes modeling the hole enlargement system based on input parameters, simulating the hole enlargement system, adjusting one or more of the input parameters, and repeating the modeling, simulating, and adjusting until a balanced condition is met.
