Patent ID: 6484826
Filing Date: 2002-11-26
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; an non-axisymmetric protrusion extending from an end of the grip portion; and an ultra hard material layer over the protrusion having an axisymmetric outer surface, wherein the critical zone is located not less than 20Â° and not greater than 80Â° 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 ultra hard material layer thickness 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, and wherein the critical zone spans an arc no greater than 180Â° around the protrusion.