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

Abstract: An object is to prolong the life of a cubic boron nitride cutting tool used for cutting a heat-resistant alloy. A cubic boron nitride cutting tool includes an edge tip made of a sintered cubic boron nitride compact having a thermal conductivity within the range of 20 to 70 W/m·K and including cubic boron nitride particles having an average particle diameter within the range of 0.5 ?m to 2 ?m; and a base metal that holds the edge tip at a corner portion of the base metal, wherein a cutting edge formed on the edge tip of the tool has a positive rake angle.

Abstract: A method for manufacturing a cubic boron nitride cutting tool including a base metal and sintered cubic boron nitride compact at a corner portion of the base metal, capable of improving the accuracy of the center height and reducing the angle of inclination or width of a negative rake face; and the cubic boron nitride cutting tool. The method includes grinding the compact by pressing it against an end face of a grindstone of a grinder to form flank and rake faces on the compact while the base metal of the cutting tool is held by a chuck of the grinder, so that the compact is substantially ground. The rake face is formed to be recessed from a top face of the base metal or only a portion of the compact that protrudes from a base-metal rake face is ground while the tool is continuously held by the chuck.