A method of making a threaded ring (24) into two (2) semicircular portions (30, 32) for fitting within a groove (19) on a journal (12) of a drill bit (10) to retain a roller cutter (20) thereon. The ring (24) is first formed with screw threads (26) about an oversized outer diameter and then cut into two semicircular portions (30, 32). The amount of the oversized outer diameter compensates for the thickness of the material removed by the cut as shown at W. If the thickness of the cut exceeds a certain amount, yielding of the ring is provided as shown in FIGS. 3-7 to provide a permanent set to compensate for the thickness W of the material removed.
A novel split threaded ring bearing member for rolling cutter drill bits with at least a portion of its threads having a different pitch than its mating threads is disclosed. The pitch difference is designed so that the threaded ring can be seated or otherwise located precisely with respect to the other bearing elements within the drill bit to effectively control the axial displacement of the rolling cutter on the bearing spindle within a given tolerance range. Upon assembly, the difference in thread pitch causes the opposite, opposing mating thread flanks to engage, effectively applying a tensile or compressive force to a portion of the threaded ring bearing member, which gradually increases as the assembly is tightened. The result is an improved rolling cutter drill bit with a threaded ring cutter bearing system with excellent resistance to back-off which will not allow significant radial movement between the engaged threads, even if some back-off of the threads occurs.
A mounting for cutter wheels on rotary rock drill bits includes a spindle with two annular axial load bearing surfaces, one of which interfaces in a rotational relationship with a cylindrical segmented bushing affixed to the inside surface of a cavity in the cutter wheel and the other of which interfaces through a top hat bushing flange in a rotational relationship with an annular end bearing surface in the cavity of the cutting wheel. A compressive silver coating on the cylindrical bushing before it is split, leaving uncoated edges for precise registration and bit onto a cylindrical race surface machined into the spindle, provides lubrication in addition to compressing under load to distribute axial loading forces from the cutter wheel in proportion to the two axial load bearing surfaces on the spindle. A small, precise, initial clearance between the annular end bearing surface in the cavity of the cutter wheel and the distal axial load bearing surface on the spindle, which clearance disappears upon initial wear-in and seating, also provides proportional axial load distribution to the two axial load bearing surfaces on the spindle. A slanted seal groove in the cutter wheel allows positioning the cylindrical bushing close to the proximal end surface while protecting the seal from a worn proximal end surface.
