Abstract: The invention comprises a cutter for a drag-type drill bit, the cutter having a stud portion defining one end thereof and a cutting formation generally adjacent the other end, said stud portion having external side walls which, throughout a major part of the length of said stud portion and in transverse cross section, define a circle interrupted by at least one section of greater radius of curvature.

Abstract: A drill bit comprises a bit body having an operating end face. A plurality of self-sharpening cutters are mounted in the bit body and extend through the operating end face. The cutters have cutting faces adapted to engage an earth formation and cut the earth formation to a desired three-dimensional profile. The cutting faces define surfaces having back rake angles which decrease with distance from the profile. The individual cutting faces may be inwardly concave in a plane parallel to the intended direction of motion of the cutter in use.

Abstract: A full bore drag type well drilling bit including a bit body comprised of a generally non-frangible metallic material. The bit body has an operating end face defined by said metallic material to include a plurality of upsets each having a leading edge and at least one recess extending through such leading edge into said metallic material. The end face further includes a plurality of flow paths, each of the leading edges of the upset having one such flow path extending therealong and inset therefrom. At least some of the upsets have a plurality of such recesses spaced therealong. A plurality of circulation ports open through the end face of the bit body, the number of circulation ports being less than the number of flow paths extending along the leading edges of the upsets, and at least some of the ports communicate with more than one such path. The bit further comprises a plurality of cutting structures carried by the bit body.

Abstract: In a rotary drilling bit having preform cutting elements, a partial or total structural discontinuity is disposed between the elements and the underlying structure or within the underlying structure to reduce the bending strain upon the preform cutting elements. In this way there is a reduction in the fracture or damage of preform cutting elements.