Patent ID: 6109377
Filing Date: 2000-08-29
Classification: E21B

Abstract:
A rotatable cutting bit for penetrating an earth formation, the bit comprising:an elongate bit body having a forward end and a rearward end, the bit body defining a peripheral surface, the bit body having a central longitudinal axis and a center of rotation;the bit body containing a first seat and a second seat at the axially forward end thereof;a first cutting insert being retained in the first seat so as to present a first clearance cutting edge which radially extends past the peripheral surface of the bit body so as to engage the earth formation, and the first cutting insert having a first leading cutting edge that engages the earth formation, and substantially all of the first leading cutting edge being disposed at a first lead angle (C) between 50 degrees and 90 degrees wherein the first lead angle (C) is the included angle between a pair of intersecting lines (E--E and F--F) wherein one line (E--E) is along the first leading cutting edge and another line (F--F) is parallel to the center of rotation of the bit body; anda second cutting insert being retained in the second seat so as to present a second clearance cutting edge which radially extends past the peripheral surface of the bit body so as to engage the earth formation, and the second cutting insert having a second leading cutting edge that engages the earth formation, substantially all of the second leading cutting edge being disposed at a second lead angle (C) between 50 degrees and 90 degrees wherein the second lead angle (C) is the included angle between a pair of intersecting lines (E--E and F--F) wherein one line (E--E) is along the second leading cutting edge and another line (F--F) is parallel to the center of rotation of the bit body.