Provided is an end mill which includes an end mill main body having a bottom blade having a convex hemispherical shape, and a hard coating film coated on at least a surface of a distal end portion of the end mill main body. A diameter D (mm) of the bottom blade is 2 mm or less. A ratio W/D of a width W (mm) of a chisel portion to the diameter D (mm) is within a range of 0.020 to 0.060. A ratio L/D of a facing length L (mm) of chip discharge grooves to the diameter D (mm) is within a range of 0.014 to 0.090. A rake angle of the bottom blade in a range in which a chisel edge is formed in the chisel portion is within a range of −15° to −30°.

An object of this disclosure is to provide a cutting insert that is shaped so that a major cutting edge is not damaged easily. In the cutting insert, a major cutting edge, a corner edge, a flat cutting edge and an inner cutting edge are formed on at least an upper surface, a protruding portion protruding outward is formed in a major cutting edge side surface portion of a side surface that corresponds to the major cutting edge, and a first section is formed in which, when viewed from above, the protrusion amount becomes smaller as the protruding portion separates from the corner edge. Furthermore, the cutting insert includes a first clearance angle changing portion in which a clearance angle becomes smaller as a major cutting edge flank portion formed in a major cutting edge side surface portion separates from the corner edge, and a second clearance angle changing portion in which the clearance angle becomes larger as the major cutting edge flank portion separates from the corner edge, wherein the first clearance angle changing portion is preferably positioned closer to the corner edge than the second clearance angle changing portion is, and, of end portions of the first clearance angle changing portion, the value of the clearance angle at a distal end portion from the corner edge is preferably negative.

A milling head for a ball track milling cutter includes an imaginary center axis, a first, working-side end and a second, clamping-side end opposite the first end when viewed along the central axis, and comprising at least one geometrically defined cutting edge, extending along a cutting edge profile of the cutting edge from a first cutting edge end facing the first end of the milling head in the direction of the second end of the milling head up to a second cutting edge end facing the second end of the milling head, wherein at least one cutting edge is formed as an intersecting line between the rake face associated with at least one cutting edge and a first flank face associated with at least one cutting edge, wherein at least one cutting edge is assigned a negative rake angle, a first clearance angle and a wedge angle. It is provided that a value of the negative rake angle in the region of the first cutting edge end has a different value than in the region of the second cutting edge end, that the first clearance angle in the region of the first cutting edge end has a different value than in the region of the second cutting edge end, and that the wedge angle along the cutting edge profile is constant.

A milling head for a ball track milling cutter includes an imaginary center axis, a first, working-side end and a second, clamping-side end opposite the first end when viewed along the central axis, and comprising at least one geometrically defined cutting edge, extending along a cutting edge profile of the cutting edge from a first cutting edge end facing the first end of the milling head in the direction of the second end of the milling head up to a second cutting edge end facing the second end of the milling head, wherein at least one cutting edge is formed as an intersecting line between the rake face associated with at least one cutting edge and a first flank face associated with at least one cutting edge, wherein at least one cutting edge is assigned a negative rake angle, a first clearance angle and a wedge angle. It is provided that a value of the negative rake angle in the region of the first cutting edge end has a different value than in the region of the second cutting edge end, that the first clearance angle in the region of the first cutting edge end has a different value than in the region of the second cutting edge end, and that the wedge angle along the cutting edge profile is constant.

A milling head for a ball track milling cutter includes an imaginary center axis, a first, working-side end and a second, clamping-side end opposite the first end when viewed along the central axis, and comprising at least one geometrically defined cutting edge, extending along a cutting edge profile of the cutting edge from a first cutting edge end facing the first end of the milling head in the direction of the second end of the milling head up to a second cutting edge end facing the second end of the milling head, wherein at least one cutting edge is formed as an intersecting line between the rake face associated with at least one cutting edge and a first flank face associated with at least one cutting edge, wherein at least one cutting edge is assigned a negative rake angle, a first clearance angle and a wedge angle. It is provided that a value of the negative rake angle in the region of the first cutting edge end has a different value than in the region of the second cutting edge end, that the first clearance angle in the region of the first cutting edge end has a different value than in the region of the second cutting edge end, and that the wedge angle along the cutting edge profile is constant.

Provided is an end mill which includes an end mill main body having a bottom blade having a convex hemispherical shape, and a hard coating film coated on at least a surface of a distal end portion of the end mill main body. A diameter D (mm) of the bottom blade is 2 mm or less. A ratio W/D of a width W (mm) of a chisel portion to the diameter D (mm) is within a range of 0.020 to 0.060. A ratio L/D of a facing length L (mm) of chip discharge grooves to the diameter D (mm) is within a range of 0.014 to 0.090. A rake angle of the bottom blade in a range in which a chisel edge is formed in the chisel portion is within a range of −15° to −30°.

A rotary cutting method includes producing a processed product by rotary cutting of a workpiece by a rotary tool. The rotary tool has at least one cutting edge of which both of a first rake angle in a rotation radial direction and a second rake angle in a rotation axis direction are negative. The at least one cutting edge has a slanted face connected with a rake face forming the first and second rake angles. The slanted face is connected with the rake face at a ridge line. The slanted face faces a rotating direction of the rotary tool. An angle of the slanted face to the rotation axis direction is positive.

An object of this disclosure is to provide a cutting insert that is shaped so that a major cutting edge is not damaged easily. In the cutting insert, a major cutting edge, a corner edge, a flat cutting edge and an inner cutting edge are formed on at least an upper surface, a protruding portion protruding outward is formed in a major cutting edge side surface portion of a side surface that corresponds to the major cutting edge, and a first section is formed in which, when viewed from above, the protrusion amount becomes smaller as the protruding portion separates from the corner edge. Furthermore, the cutting insert includes a first clearance angle changing portion in which a clearance angle becomes smaller as a major cutting edge flank portion formed in a major cutting edge side surface portion separates from the corner edge, and a second clearance angle changing portion in which the clearance angle becomes larger as the major cutting edge flank portion separates from the corner edge, wherein the first clearance angle changing portion is preferably positioned closer to the corner edge than the second clearance angle changing portion is, and, of end portions of the first clearance angle changing portion, the value of the clearance angle at a distal end portion from the corner edge is preferably negative.

In an indexable rotary cutting tool of the present invention, a cutting edge portion of an insert includes a peripheral cutting edge, a bottom cutting edge, a cutting edge of a corner R, and a chamfered surface, a radial rake angle () of the cutting edge of the corner R has a negative value in an entire edge length region of the cutting edge of the corner R, and the radial rake angle () becomes a minimum value at an intermediate portion located between a pair of boundary points (P, Q) in the cutting edge of the corner R.

In an indexable rotary cutting tool of the present invention, a cutting edge portion of an insert includes a peripheral cutting edge, a bottom cutting edge, a cutting edge of a corner R, and a chamfered surface, a radial rake angle () of the cutting edge of the corner R has a negative value in an entire edge length region of the cutting edge of the corner R, and the radial rake angle () becomes a minimum value at an intermediate portion located between a pair of boundary points (P, Q) in the cutting edge of the corner R.