Abstract: The present invention relates to diamond drag bits having cylindrical polycrystalline diamond faced inserts with a convex cutting surface, the insert being imbedded in the cutting face of a drag bit. The invention teaches an optimization of the geometry of the cutting face of cutting elements, particularly of the type in which a diamond layer is adhered to a cemented carbide substrate to form a composite, and the composite is bonded to a support stud or cylinder. The convex curvature radius is maximized to the extent that the best shear action on the earthen formation is achieved. The resultant side rake angle assures that each insert remains free of detritus presenting a clean cutting edge to the formation.

Abstract: A drag bit for soft formation is disclosed which consists of a new cutting mechanism. The drag bit face forms one or more pairs of radially disposed ridges separated by a valley whereby a leading ridge supports multiple rounded projections and the following ridge supports multiple positive rake angle cutters. The rounded projection elements move aside an elastic earth formation and the separated and trailing cutters clip off the dislodged formation to advance the bit in a borehole.