Patent ID: 6481511
Filing Date: 2002-11-19
Classification: B22F,C04B,E21B,F16C,Y10T

Abstract:
A rotary drill bit comprising a bit body having an axis of rotation, and a plurality of cutters arranged in concentric rings centered on the axis of rotation, the plurality of cutters comprising a first type of cutter of a relatively low abrasion resistance and a second type of cutter of a relatively high abrasion resistance, at least one of the rings consisting of cutters of the first type, at least another of the rings including at least one cutter of the second type, wherein the first type of cutter has substantially the same impact toughness as the second type of cutter, and wherein each cutter of the second type comprises a table of polycrystalline diamond which defines a matrix of interstices containing a catalyzing material, and wherein the interstices close to a working surface of the table contain less catalyzing material than the interstices spaced from the working surface.