Cutting element geometry for roller cone drill bit

摘要

A roller cone drill bit for drilling earth formations is disclosed. The bit includes a bit body and a plurality of roller cones attached to the bit body and able to rotate with respect to the bit body. The drill bit includes plurality of cutting elements disposed on each of the roller cones such that at least one of the cutting elements includes a step shaped crest on its outer surface. In one embodiment, the step shaped crest includes a difference in extent between a more extensive and less extensive crest segment selected to correspond to a penetration depth in a particular earth formation at which fracture failure is expected. Other embodiments include one or more flank surfaces having more and less extensive surfaces thereon corresponding to the more and less extensive crest segments.