Patent ID: 9492877
Filing Date: 2016-11-15
CPC Classification: B23B,Y10T

Claim Text:
1. A drill comprising: a chip discharge flute opened in a tip surface; and a cutting edge formed at an intersecting portion between an inner wall surface of the chip discharge flute on a side of a drill rotation direction and a tip flank formed on the tip surface, the cutting edge being made up of a concavely-curved cutting edge portion formed on an inner circumferential side and a convexly-curved cutting edge portion formed on an outer circumferential side, a cross section orthogonal to an axial center having a first convex curve corresponding to the convexly-curved cutting edge portion and a first concave curve corresponding to the concavely-curved cutting edge portion intersecting with each other at an intersection, and a ridgeline being formed at the intersection.