A cubic boron nitride sintered material tool contains a plurality of cBN grains. cBN grains located on a surface of the cutting edge contain a cubic boron nitride phase, and a hexagonal boron nitride phase. When a ratio I.sub.*/I.sub.* between an intensity of a * peak derived from a bond of hBN in the hexagonal boron nitride phase and an intensity of a * peak derived from a bond of hBN in the hexagonal boron nitride phase and a bond of cBN in the cubic boron nitride phase is determined by measuring an energy loss associated with excitation of K-shell electrons of boron, the ratio I.sub.*/I.sub.* of the cBN grain on the surface of the cutting edge is 0.1 to 2, and the ratio I.sub.*/I.sub.* of the cBN grain at a depth position of 5 m from the surface of the cutting edge is 0.001 to 0.1.

A base material for a hard sintered body includes a pillar portion having a central axis and extending in the axial direction of the central axis. The pillar portion has a first outer peripheral portion, a second outer peripheral portion, and a protruding stripe portion. In the cross-sectional view, one side portion of the first outer peripheral portion extending in a circumferential direction or a radial direction is located inside the other side portion. In the cross-sectional view, one side portion of the second outer peripheral portion extending in the circumferential direction or the radial direction is located outside the other side portion in the radial direction. The protruding stripe portion is located in a connection portion between the other side portion of the first outer peripheral portion and one side portion of the second outer peripheral portion, and protrudes outward.

This milling cutter includes: a blade part 10 having a plurality of tips 12 each having an end cutting edge 121 and a peripheral cutting edge 122, and a blade-body portion 11 which is a plate-shaped body with the plurality of tips 12 fixed to an outer circumference thereof and has a groove 113 in accordance with a position of each tip; and a body 20 being rotatable around a rotational axis and having a front-end portion 21 having a front-end surface to which a rear-end surface of the blade-body portion 11 is fixable detachably and in close contact therewith, and a front-end outer-circumferential portion whose outer diameter is 100/100 to 97/100 using an outer diameter of the blade part 10 as a reference, the front-end outer-circumferential portion having a body-side groove 211 continuous to the groove 113 of the blade-body portion 11 contacted closely.

A cutting insert includes a substrate and a cutting-edge insert. The substrate has, in a thickness direction of the substrate, a bottom surface, and a top surface opposite to the bottom surface. The top surface has a polygonal shape composed of a plurality of sides in a plan view as seen along the thickness direction. The top surface is provided with a projection projecting to a side opposite to the bottom surface along the thickness direction. The projection has a through-hole passing through the substrate along the thickness direction. The projection has a side surface contiguous to the top surface. The side surface is composed of a curved line protruding to a side opposite to the through-hole in the plan view as seen along the thickness direction.

A method for producing a coated cutting tool for metal machining having a substrate and coating is provided. The coating includes at least one layer of (Ti,Al)N having a cubic crystal phase. The method includes the deposition of a layer of Ti.sub.1-xAl.sub.xN, 0.70x0.98, the Ti.sub.1-xAl.sub.xN having cubic crystal phase. The layer of Ti.sub.1-xAl.sub.xN is deposited by cathodic arc evaporation at a vacuum chamber pressure of from 7 to 15 Pa of N.sub.2 gas, using a DC bias voltage of from 200 to 400 V and using an arc discharge current of from 75 to 250 A. A coated cutting tool for metal machining having a coating including a (Ti,Al)N multi-layer of alternating sub-layers of at least Ti.sub.1-yAl.sub.yN and Ti.sub.1-zAl.sub.zN, 0.35y0.65 and 0.80z0.98, with only cubic phase present is also provided.