US Patent 7168511 Rotary drill bit having cutting insert with a notch

A rotary drill bit insert that includes an elongate body that is rotatable about a central axis wherein the elongate body has a pair of symmetrical halves symmetrical about the central axis. The elongate body contains a central notch disposed between the symmetric halves of the elongate body. Each symmetrical half includes a leading face and a top surface that has a leading surface and a trailing relief surface wherein the leading surface and the trailing relief surface are contiguous and non-coplanar. Each half also has a leading cutting edge at the intersection of the leading face and the leading surface of the top surface. The leading surface is inclined at a constant angle of inclination in a radial direction with respect to a first radial line projecting from the central axis, and the leading surface being inclined downwardly and rearwardly from the leading cutting edge.