Drill bit

A drill bit comprising:

• a body of a cylindrical shape having a face at its forward end and a straight groove of a generally V-shape including two side faces and a corner into which said faces merge;
• said groove being formed in the circumferential surface thereof and extending along the longitudinal axis of the bit body;
• said corner being disposed in the vicinity of the longitudinal axis of said bit body;
• said bit body having a drilling fluid passageway extending longitudinally through said bit body and opening to said end face;
• one of said two side faces having semi-cylindrical convex surface extending radially outwardly from said corner and a flat surface extending radially outwardly from said semi-cylindrical surface to the periphery of said cylindrical bit body;
• said semi-cylindrical surface and said flat surface extending along the longitudinal axis of said bit body;
• said semi-cylindrical surface terminating at its forward end in an arcuate inward cutting edge while said flat surface terminates at its forward end in a straight outward cutting edge;
• said arcuate inward cutting edge and said straight outward cutting edge sloping radially outwardly in a direction away from said forward end of said drill bit body;
• said forward end of said drill bit having an apex in the vicinity of said longitudinal axis, and the inner end of said arcuate inward cutting edge being disposed at said apex of said forward end;
• and
• said arcuate inward cutting edge being offset from said straight outward cutting edge when viewed from the forward end of said bit body.