A cutting tool assembly for milling a rail top, includes a first section and a second section mounted to the first section. Each section includes a plurality of insert-receiving pockets for receiving a plurality of different types of cutting inserts. The plurality of different types of cutting inserts are arranged in a plurality of helical teeth that may be separated by a helical chip flute. In one embodiment, a first type of cutting insert is formed with a radius, R, a second type of cutting insert is formed with a radius, R1, and a third type of cutting insert is formed with a radius, R2, to perform a milling operation on three different areas of the rail top.

A cutting insert may include a first surface having a polygonal shape, a second surface, and a cutting edge located on a ridge line where the first surface intersects with the second surface. The first surface may include a first corner, a second corner, a third corner, a first side, and a second side. In a plan view of the first surface, the first side may have a straight line shape or a convex shape protruded outward relative to a first imaginary line connecting the first corner and the second corner, and the second side may have a concave shape recessed inward relative to a second imaginary line connecting the first corner and the third corner.

A drill bit for cutting formation comprises a bit body, a plurality of cutters, and a plurality of blades with pockets to accommodate the cutters, respectively. In an embodiment, the plurality of cutters comprise a substrate, an ultra-hard layer, a concave surface on the top of the ultra-hard layer, wherein the concave surface comprises a plurality of planar and curved surfaces.

A cutting insert for a rotary cutting tool has a second surface that includes a second seating surface having a shape of a flat surface. The first cutting edge has a first main cutting edge portion and a first sub cutting edge portion. The second cutting edge has a second main cutting edge portion and a second sub cutting edge portion. When viewed in a direction from the first surface toward the second surface, at least a portion of the second sub cutting edge portion is located outside the first main cutting edge portion, and at least a portion of the first sub cutting edge portion is located outside the second main cutting edge portion. When viewed in the direction from the first surface toward the second surface, each of the first sub cutting edge portion and the second sub cutting edge portion has a shape of a curved line.

A cutting insert which is excellent in both cutting edge strength and chip evacuation is provided. A corner edge of the cutting insert is formed in an arc shape. In a direction perpendicular to a rotation axis of a body, a width of the corner edge is 40% or more and 50% or less of a width of the cutting insert. An upper surface has a negative land which is formed along a cutting edge and has a negative angle. The angle of the negative land increases from one end, which is connected to an inner cutting edge, of both ends of the corner edge toward the other end.

A ridgeline between the top surface and the side surface includes: a nose cutting edge portion having a curved line shape, the nose cutting edge portion having a first end and a second end opposite to the first end; a major cutting edge portion contiguous to the first end; and a wiper cutting edge portion contiguous to the second end. The top surface includes: a first rake face contiguous to the wiper cutting edge portion; a second rake face contiguous to the major cutting edge portion; and a third rake face contiguous to the nose cutting edge portion and contiguous to each of the first rake face and the second rake face. A boundary line between the second rake face and the third rake face is separated from the first end and is contiguous to the major cutting edge portion.

A cutting insert which is excellent both in manufacturing performances and dimensional precision and forms a pair with a tool body and a gear cutter including the cutting insert are provided. A cutting insert has a first face which is a rake face, a second face, a peripheral side face, and a mounting hole. On a ridge line where the first face and the peripheral side face cross each other, a cutting blade is formed. The cutting blade includes a corner part capable of machining a tooth bottom of a gear, and a main part extending to the corner part. The peripheral side face includes an inner side face in contact with a tool body and a first flank facing the main part. The mounting hole penetrates the first flank and the inner side face so that a center axis crosses the inner side face perpendicularly. The cutting insert is formed having a wedge shape such that thickness of the first flank and the inner side face becomes smaller as it goes from one end to the other end.

A double-sided, polygonal cutting insert includes a first surface and a second surface opposite the first surface. A plurality of side surfaces extend between the first surface and the second surface. A plurality of primary concave cutting edges are formed at an intersection between the plurality of side surfaces and the first and second surfaces, and a plurality of convex wiper edges are formed at an intersection between the plurality of side surfaces and the first and second surfaces. Each wiper edge has a step extending radially outward from a respective side surface. The cutting insert is mounted in a cutting tool such that the primary cutting edge and a wiper edge contact a workpiece to produce a high-quality surface finish on the workpiece.

A cutting insert 2 comprises a peripheral side surface 30 which is parallel to a central axis O of a first end surface 10 and a second end surface 20. The peripheral side surface 30 comprises a first side surface 31 facing a first major cutting edge 11, a second side surface 32 facing a first wiper edge 12, and a third side surface 33 facing a first inner edge 13. A flank 311 of the first major cutting edge 11 and a flank 321 of the first wiper edge 12 are inclined such that the flank 311 and 321 approaches the central axis O as it heads toward the first end surface 10. The flank 311 of the first major cutting edge 11 is located on a different plane from the first side surface 31. The flank 321 of the first wiper edge 12 is located on a different plane from the second side surface 32. Meanwhile, a flank of the first inner edge 13 is located on the same plane as the third side surface 33.

A cutting insert for a milling tool is provided. A longitudinal plane extends halfway between a first pair of opposing side surfaces of the cutting insert. A first axial relief face adjacent to the a auxiliary cutting edge and a first axial abutment face form part of a first surface grouping on a first side of the longitudinal plane, and a second axial relief face adjacent to a second auxiliary cutting edge and a second axial abutment face form part of a second surface grouping on a second side of the longitudinal plane. The first surface grouping and the second surface grouping meet in a partitioning line, wherein the partitioning line extends in the longitudinal plane , and wherein the partitioning line extends from the first side to the second side.