A cutting insert according to an embodiment has a polygonal shaped upper surface, a lower surface, a side surface, and a cutting edge. The cutting edge has an arc-shaped first corner edge, an arc-shaped second corner edge, and a wiper edge located between the first corner edge and the second corner edge. The wiper edge has an arc-shaped first wiper edge and an arc-shaped second wiper edge located closer to the second corner edge than the first wiper edge. R0<R1<R2 is satisfied wherein R1 is a radius of curvature of the first wiper edge, R2 is a radius of curvature of the second wiper edge, and R0 is a radius of curvature of each of the corner edges in a top view.

A rotary cutting tool, which is excellent in defect resistance and has a stable lifespan, includes a rake surface composed of one surface, a cutting edge angle that is larger than 0? and smaller than 90?, a true rake angle that is not smaller than ?42? and not larger than ?13?, and a major cutting edge inclination angle that is not smaller than ?5? and smaller than +5?. A wiper insert is preferably formed in a rounded convex shape.

A cutting insert according to an embodiment has a lower surface, an upper surface, a side surface disposed between the lower surface and the upper surface, a pair of corner cutting edges located along an intersection of the upper surface and the side surface, and a major cutting edge located between the pair of corner cutting edges. The major cutting edge has a downwardly dented curvilinear part and a pair of straight parts respectively extending from the curvilinear part toward the pair of corner cutting edges in a side view. A portion of the curvilinear part located lowermost is close to one corner cutting edge in the side view.

A cutting insert (1) according to an embodiment has a lower surface (2), an upper surface (3), a side surface (4) disposed between the lower surface (2) and the upper surface (3), a pair of corner cutting edges (5) located along an intersection of the upper surface (3) and the side surface (4), and a major cutting edge (6) located between the pair of corner cutting edges (5). The major cutting edge (6) has a downwardly dented curvilinear part (61) and a pair of straight parts (62) respectively extending from the curvilinear part (61) toward the pair of corner cutting edges (5) in a side view. A portion (6p) of the curvilinear part (61) located lowermost is close to one corner cutting edge (5b) in the side view.

A cutting insert according to an embodiment has a polygonal shaped upper surface, a lower surface, a side surface, and a cutting edge. The cutting edge has an arc-shaped first corner edge, an arc-shaped second corner edge, and a wiper edge located between the first corner edge and the second corner edge. The wiper edge has an arc-shaped first wiper edge and an arc-shaped second wiper edge located closer to the second corner edge than the first wiper edge. R0<R1<R2 is satisfied wherein R1 is a radius of curvature of the first wiper edge, R2 is a radius of curvature of the second wiper edge, and R0 is a radius of curvature of each of the corner edges in a top view.

A cutting insert according to an embodiment has a polygonal shaped upper surface, a lower surface, a side surface, and a cutting edge. The cutting edge has an arc-shaped first corner edge, an arc-shaped second corner edge, and a wiper edge located between the first corner edge and the second corner edge. The wiper edge has an arc-shaped first wiper edge and an arc-shaped second wiper edge located closer to the second corner edge than the first wiper edge. R0<R1<R2 is satisfied wherein R1 is a radius of curvature of the first wiper edge, R2 is a radius of curvature of the second wiper edge, and R0 is a radius of curvature of each of the corner edges in a top view.

A cutting insert for a milling tool including an upper side having a central surface, a lower side, a peripheral side surface, and a cutting edge formed between the upper side and the peripheral side surface. The cutting edge having a positively inclined main cutting edge projecting at least partly above the central surface. The upper side includes a rake surface extending inside of and along the at least one cutting edge, sloping downward toward the central surface. A plateau, elevated with respect to the central surface and extending along the main cutting edge, is formed inside the rake surface. A transition between the rake surface and the plateau extends at an angle .sub.2 with respect to an upper extension plane, wherein .sub.2>0.

The disclosure relates to a cutting insert for a tool for machining a workpiece, comprising: two identical mutually opposite base surfaces, wherein at least a part of each base surface is orthogonal to a z-axis of the cutting insert, two identical mutually opposite main side surfaces which extend between the two base surfaces, wherein at least a part of each main side surface is oriented orthogonally to an x-axis of the cutting insert, and two identical mutually opposite secondary side surfaces which extend between the two base surfaces, wherein at least a part of each secondary side surface is oriented orthogonally to a y-axis of the cutting insert, wherein the x-, y- and z-axes are main axes of the cutting insert that are oriented orthogonally to one another, wherein between each one of the base surfaces and each one of the main side surfaces a main cutting edge is arranged, and wherein each main side surface has two diagonally opposite first segmental cutting edges, wherein each first segmental cutting edge adjoins a first end of the respective main cutting edge, wherein the main cutting edges and the first segmental cutting edges of each main side surface are each located in a cutting edge plane which extends orthogonally to the x-axis, wherein the first segmental cutting edges are each arranged on a first protrusion which is arranged on each of the secondary side surfaces and defines a first clearance angle.

A cutting insert includes an insert body having a polygonal plate shape. Rake faces are formed on polygonal surfaces of the insert body, and flank faces are formed on lateral faces of the insert body arranged around the polygonal surfaces. Main cutting edges are formed on side ridges of the polygonal surfaces at intersecting ridgelines between the rake faces and the flank faces. Each main cutting edge extends between two corners adjacent to each other in a circumferential direction of the polygonal surface among corners of the polygonal surface. When seen from a direction opposing the rake face, one end portion of the main cutting edge that stretches to one corner of the two corners has a convexly curved shape, and the other end portion of the main cutting edge that stretches to the other corner of the two corners has a concavely curved shape.

A rake surface of a cutting insert according to the present disclosure is formed with a first plane parallel to a seating surface. An outer periphery of the first plane includes a plurality of curved portions having different radii of curvature. On the rake surface, a breaker is provided between a cutting edge portion and the first plane around an entire circumference of the cutting insert. When a distance from the seating surface to a tip of the cutting edge portion in a thickness direction is denoted by L11, a distance from the seating surface to the first plane in the thickness direction is denoted by L12, and a distance from the seating surface to a deepest portion of the breaker in the thickness direction is denoted by L13, a relationship of L11>L12>L13 is satisfied over an entire circumference of the cutting edge portion.