Patent ID: 6860344
Filing Date: 2005-03-01
Classification: E21B

Abstract:
1. A rotary drill bit for penetrating earth strata, the drill bit comprising: an elongate bit body having an axial forward end; and a monolithic hard insert being affixed to the bit body at the axial forward end thereof, said hard insert having a trio of symmetric lobes, each said lobe having a discrete stepped leading cutting edge, each said stepped leading cutting edge having a straight upper step, a transition portion connected to said upper step and a straight lower step connected to said transition portion, said upper step of said leading cutting edge having an upper leading surface, said upper leading surface disposed at a rake angle with the vertical of between about five degrees to about negative fifteen degrees, said lower step and said transition portion of said leading cutting edge having a lower leading surface disposed at a rake angle with the vertical of between about zero degrees to about negative ten degrees.