CUTTING INSERT AND CUTTING TOOL

摘要

A cutting tool includes a cutting insert 4 that is held in a holder in a detachable manner. The cutting insert 4 has a substantially regular quadrangular shape in plan view and includes four round corners 4a. The cutting insert 4 is formed of CBN sinter as a whole. The cutting insert 4 includes two principal surfaces 6 that are upper and lower surfaces opposite to each other, and four side surfaces 7 that are arranged so as to connect the principal surfaces 6 to each other. A boundary portion (ridge line portion) between each of the principal surfaces 6 and each of the side surfaces 7 forms a cutting edge 8. In a central portion of each of the side surfaces 7 of the cutting insert 4, a groove 10 for absorbing a crack, having a substantially V-shape in cross section, is formed all around the cutting insert 4 so as to be recessed with respect to the side surfaces 7.