A rotary tool may include a main body having a circular columnar body, including a rotation axis and extending from a first end to a second end. The main body may include first flutes, second flutes, a first cutting edge, and a second cutting edge. The first flutes may have a helix angle θ1 and the second flutes a reverse helix angle θ2. The first cutting edge may be located on a ridge line where the outer periphery of the main body intersects with the first flutes and the second cutting edge at a ridge line where the outer periphery of the main body intersects with the second flutes. The θ2 may be larger than the θ1, m≥5, m−n≥3, and m and n are coprime numbers, where m is the number of the first flutes and n is the number of the second flutes.

A rotary tool may include a main body having a circular columnar body, including a rotation axis and extending from a first end to a second end. The main body may include first flutes, second flutes, a first cutting edge, and a second cutting edge. The first flutes may have a helix angle 1 and the second flutes a reverse helix angle 2. The first cutting edge may be located on a ridge line where the outer periphery of the main body intersects with the first flutes and the second cutting edge at a ridge line where the outer periphery of the main body intersects with the second flutes. The 2 may be larger than the 1, m5, mn3, and m and n are coprime numbers, where m is the number of the first flutes and n is the number of the second flutes.

A cutting tool has a cutting body with a first insert pocket and an indexable cutting insert removably mounted therein. The first insert pocket has a first seat surface with a plurality of first engagement elements and a first support wall transverse thereto. The cutting insert has upper and lower surfaces and a boundary surface extending therebetween. The lower surface has a plurality of lower engaging elements and the boundary surface has a plurality of alternating first and second peripheral surfaces intersecting the upper surface to form first and second upper cutting edges. In each index position with the lower surface in contact with the first seat surface, the first support wall prevents translation of the cutting insert in a first direction, and the first engagement elements eccentrically contact the lower engaging elements to prevent translation of the cutting insert in a second direction perpendicular to the first direction.

A cutting tool has a cutting body with a first insert pocket and an indexable cutting insert removably mounted therein. The first insert pocket has a first seat surface with a plurality of first engagement elements and a first support wall transverse thereto. The cutting insert has upper and lower surfaces and a boundary surface extending therebetween. The lower surface has a plurality of lower engaging elements and the boundary surface has a plurality of alternating first and second peripheral surfaces intersecting the upper surface to form first and second upper cutting edges. In each index position with the lower surface in contact with the first seat surface, the first support wall prevents translation of the cutting insert in a first direction, and the first engagement elements eccentrically contact the lower engaging elements to prevent translation of the cutting insert in a second direction perpendicular to the first direction.

A multi-flute endmill including a cutting edge part having multiple cutting edges and flutes formed between adjacent cutting edges in a rotation direction around the tool axis O. A rake face of each cutting edge is formed from a rake face of an end cutting edge from the tool axis O side to the outer peripheral side of a shank, an adjacent rake face of a corner R edge that forms a surface different from the rake face of the end cutting edge, and an adjacent rake face of a peripheral cutting edge that forms a surface different from the rake face of the corner R edge. A gash is formed between the rake face of the end cutting edge and a flank of an end cutting edge that is adjacent on a forward side thereof in the rotation direction R.