SINGLE-EDGE DRILL FOR FORMING A DEEP HOLE

A single-edge drill for forming a deep hole is provided which includes a body (2) and a shank (3). The body (2) has a single chip discharge groove (5) in the outer periphery thereof, and includes a small-diameter portion (2b), and a large-diameter portion (2a) having coolant delivery grooves (8) in the outer periphery thereof. The body (2) has a core thickness at the distal end portion of the large-diameter portion (2a). At the other portion of the body (2), the groove bottom (5a) of the chip discharge groove (5) is located beyond the rotation center (O) of the drill such that the body (2) has no core thickness, and when taken perpendicularly to the axial direction of the drill, the cross section of the body (2) has a crescent shape. When a hole is formed with the drill using an external oil supply method, a supply path for coolant liquid is defined between the outer peripheral surface of the small-diameter portion (2b) and the radially inner surface of the hole.