Patent ID: 6460637
Filing Date: 2002-10-08
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 non-axisymmetric protrusion extending from an end of the grip portion; and an ultra hard material layer over the protrusion having an non-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 is greater within the critical zone than outside of the the critical zone, wherein the ultra hard material layer outer surface comprises a high portion defining a cutting element maximum height level as measured from a base of the grip along a longitudinal axis parallel to the central axis of the cutting element, wherein the height level of any portion of the ultra hard material layer outer surface other than the high portion as measured from the grip base along a longitudinal axis parallel to the central axis of the cutting element is not greater than the maximum height level, and wherein the outer surface of the ultra hard material layer within the critical zone does not extend to the maximum height level.