Patent attributes
A cutting insert includes a rake face, a flank surface, and a cutting edge, the cutting edge includes a bottom cutting edge that is positioned at a front end in a central axis direction and forms a convex arc shape and an outer peripheral cutting edge aligned with a radial-direction outer end of the bottom cutting edge and forms a convex arc shape of which a curvature radius is larger than that of the bottom cutting edge, an angle formed between a tangent line to a boundary point between the bottom cutting edge and the outer peripheral cutting edge and the central axis is less than 45°, a curvature radius R1 of the bottom cutting edge is 0.3 to 10 mm, and a ratio (R2/R1) of a curvature radius R2 of the outer peripheral cutting edge to the curvature radius R1 of the bottom cutting edge is 3.6 to 333.
