Drill bit cutters and drill bits equipped with the cutters. The cutter is mounted on a bit to present the formation with a radiused, curving, side wall cutting face that is concave in one dimension and convex in another dimension. In a preferred form, the cutting face is in the form of a portion of a surface of revolution generated by an arc segment that is concave relative to the axis of revolution. The cutting face is formed on a layer of polycrystalline diamond disposed on a substrate of tungsten carbide. In another side wall cutter arrangement, a standard cylindrical cutter with a diamond cap is mounted to present the curved cylindrical side of the cap to the formation. Curved side wall cutting faces cut more efficiently than the usual flat end face of conventionally mounted cutters. A major portion of the diamond volume in a side mounted cutter trails the point of cutting face engagement with the formation to provide impact resistance and an increased diamond wear area. The radiused face cutter may be mounted in any orientation on the bit. When mounted conventionally, such that the axis of the cutter is inclined away from the bit and into the direction of bit rotation, the cutter end surface rather than the side wall cuts the formation. In this orientation, the rake of the cutter may be increased to place a second cutting surface into engagement with the formation to provide two cutting surfaces.
A rolling cone drill bit is provided that has gage inserts on the first row from the bit axis to cut to full gage diameter that have a cutting portion enhanced with a layer of super abrasive material. The gage cutting surface has a center axis that is canted to be more normal to the gave curve such that its point of contact at gage is away from the thinner portion of the layer of super abrasive material.
A drill bit has a plurality of cemented carbide buttons embedded in a front end of the drill body. Each button includes a cemented carbide body having a rear mounting portion embedded in the drill body, and a symmetrically shaped crushing end protruding from the drill body. The buttons are oriented at a first acute angle of from about 35.degree. to about 55.degree. relative to the rotational center axis of the drill bit. The crushing end of the button includes at least one annular groove defining axially spaced local maximum points at each side of the groove. An imaginary line touching the maximum points defining a second acute angle relative to the center line of the button. The second angle is smaller than the first acute angle.
A rolling cone drill bit is provided that has gage inserts on the first row from the bit axis to cut to full gage diameter that have a cutting portion enhanced with a layer of super abrasive material. The gage cutting surface has a center axis that is canted to be more normal to the gage curve such that its point of contact at gage is away from the thinner portion of the layer of super abrasive material.
A preform cutting element, for a rotary drag-type drill bit, includes a facing table of polycrystalline diamond having a front face, a peripheral surface, and a rear surface bonded to the front surface of a tungsten carbide substrate. The facing table has at least one peripheral locking portion projecting rearwardly from the rear surface of the facing table into the substrate, the inner surface of the locking portion and the adjacent part of the substrate having interengaging formations whereby part of the substrate overlies at least one part of the locking portion. With this arrangement, forces acting on the facing table tending to lift it from the front surface of the substrate are resisted by the portion of the substrate which overlies the part of the locking portion.
Asymmetrical compacts are utilized in certain places on roller cones of an earth boring bit to increase the number of compacts in certain rows. The compacts that are pressed into holes in rows on the cones. The compacts are of tungsten carbide and have a cutting end axis and a barrel axis. The barrel axis intersects the cutting end axis at an obtuse angle. In the heel row, the barrel axis of at least some of the compacts is rotated to have less inclination than the cutting end axis. In an adjacent row to the heel row, each of the compacts has a barrel axis that is rotated to have more inclination than its cutting end axis and more inclination than the barrel axes of the heel row.
