Drill

Abstract

A drill includes a cutting edge having a ridgeline. The ridgeline has a part of an ellipse and a straight line. It is assumed that the coordinates of a separation point of an ellipse portion from a straight line portion are (x0, y0). The straight line is a tangent to the ellipse at the separation point. It is assumed that a1 is an area from a tip end of the drill to x0, a2 is an area from x0 to the origin of the ellipse, and a3 is a negative area, along the x-axis. The ridgeline of the cutting edge is formed straight along the tangent in the area a1, and is formed along the ellipse in the area a2. A margin is formed in the area a3 continuously from a relief face of the cutting edge.

Dependencies are inferred from the claim text.