Patent ID: 6199645
Filing Date: 2001-03-13
Classification: E21B

Abstract:
A rock bit comprising cutting elements for cutting earth formations wherein a cutting element having a central axis is mounted on the bit for contacting the earth formation within a critical zone defined on the cutting element, wherein the cutting element comprises:a grip portion;a protrusion extending from an end of the grip portion, wherein the protrusion is axisymmetric about the central axis; andan ultra hard material layer over the protrusion having a convex outer surface axisymmetric about the central axis, wherein the critical zone is located not less than 20.degree. and not greater than 80.degree. from the central axis as measured from the intersection of the central axis with the plane of intersection between the protrusion and the grip, and wherein the thickness of the ultra hard material layer as measured at any point outside the critical zone is less than the thickness of the ultra hard material layer at all points within the critical zone.