Patent ID: 8281881

Claim:
A rolling cone drill bit for drilling a borehole in earthen formations, the bit comprising: a bit body having a bit axis; a rolling cone cutter mounted on the bit body and adapted for rotation about a cone axis in a cutting direction; at least one transition insert mounted to the cone cutter at a first radial position relative to the bit axis; a first asymmetric insert mounted to the cone cutter at the first radial position or radially inward of the first radial position relative to the bit axis; a second asymmetric insert mounted to the cone cutter at a second radial position that is radially outward of the first radial position relative to the bit axis wherein each of said first and second asymmetric inserts is symmetric about a first plane along the central axis of the insert, and wherein each of said first and second inserts is not symmetric about a second plane along said central axis of said insert, wherein said second plane is perpendicular to said first plane and is parallel to, or coplanar with, a third plane along the cone axis; wherein each insert includes a base portion having a central axis and a cutting portion extending from the base portion and including a cutting surface; and wherein the cutting surface of the first asymmetric insert has a leading side relative to the cutting direction with a leading geometry and the cutting surface of the second asymmetric insert has a leading side relative to the cutting direction with a leading geometry that is different than the leading geometry of the first asymmetric insert, and wherein the first insert has a trailing side disposed 180° from the leading side of the first insert, and the second insert has a trailing side disposed 180° from the leading side of the second insert; and wherein the trailing side of the first insert has a first trailing geometry and the trailing side of the second insert has a second trailing geometry that is different from the first trailing geometry.