Patent ID: 9656328
Date: 2017-05-23
CPC Classifications: B23B,Y10T

Claim:
1. A cutting tool, comprising: a tip part having a cutting edge including a coating extending continuously from a rake face onto a flank face, a material of the coating having a higher wear resistance than a base material of the cutting edge, wherein the cutting edge has a top ridge line with a convex curve such that a radial distance of the top ridge line from a longitudinal central axis of the tip part increases as the top ridge line extends rearward in a forward-rearward direction of the cutting tool, the cutting edge comprises a forward-most cutting edge maximum radius position, and a rear auxiliary cutting edge that extends rearward from the forward-most cutting edge maximum radius position, the rear auxiliary cutting edge having a point angle of zero, the cutting edge has a flank face relief angle of not less than 15 degrees, and the tip part is configured such that, during cutting of a work, an edge of the coating on the rake face at a top of the cutting edge is worn by friction with the work; with a progress of a wear inward in a radial direction, an edge of the coating on the flank face at the top of the cutting edge is removed by friction with the work to expose the base material thereunder; and the exposed base material is worn by friction with the work to retract the flank face inward in the radial direction, and the cutting edge is configured such that, upon the base material of the cutting edge being exposed due to wearing of the coating by friction with the work, a ratio of an area of contact between the coating along the flank face and the work relative to an area of contact between the coating along the rake face and the work is from about 1.5:1 to about 3:1.