Drill and throwaway tip

摘要

A drill including a substantially columnar tool body having an axis. The tool body includes a pair of chip ejection grooves formed in an outer peripheral surface thereof. The tool body further includes, in a distal end portion thereof, a pair of cutting edges provided at respective distal ends of the pair of chip ejection grooves and a recess communicating with the pair of chip ejection grooves. The pair of cutting edges have radially inner ends located in positions slightly offset from the axis radially outward, and the recess extends along the axis while passing a gap between the radially inner ends of the pair of cutting edges, and has a bottom surface facing a distal end of the tool body. The bottom surface of the recess includes one slope and another slope. The one slope obliquely crosses the axis in a position aligned with the axis and inclines toward one of the pair of chip ejection grooves as the one slope proceeds to a side near a base end of the tool body, and the other slope crosses the one slope on a side near the distal end of the tool body and inclines toward another of the pair of chip ejection grooves as the other slope proceeds to the side near the base end of the tool body.