Rotary drill bit having drag cutting elements

Abstract

A rotary drill bit comprising a bit body having a plurality of drag cutting elements mounted on the bottom thereof. Each cutting element has a portion projecting down below the bit body and forward generally in the direction of rotation of the bit. This portion presents a leading face and a trailing face which converge at an acute angle to form a cutting edge. Each element is positioned on the bit body such that its leading and trailing faces present a positive rake angle and back clearance, respectively, to the surface of the well bore formation for improved cutting action. The bit body has an exit port at the bottom thereof for flow of drilling fluid under pressure, and sets of first and second generally parallel ridges defining watercourses extending from the exit port to the periphery of the bit. The cutting elements are mounted on the second or trailing ridge, and extend toward but stop short of the first or leading ridge. The leading face and cutting edge of each element thus extend into the watercourse and are cooled and cleaned by the drilling fluid. In addition the leading ridge extends down to a level below the bottom of the trailing ridge but above the cutting edges for limiting the depth of penetration of the cutting element.