A cutting insert is configured to include: a first portion having a rake face, a flank face, a cutting edge, and a face facing an insert attachment portion at an end of a tool main body; and a second portion having a side surface including at least one flat plane that is parallel to a center line of a tool or inclined at a prescribed angle to the center line. The second portion extends continuously to a region surrounded by the face of the first portion. The second portion is fitted into the tool main body to position the cutting insert and to prevent the cutting insert from rotating.

Provided is a cutting insert, within which a burr being generated at an outer edge of a finished surface is inhibited and chipping of the cutting insert is inhibited even when the cutting insert is formed to have multiple corners superior in economical efficiency. The cutting insert has an upper surface, a lower surface on an opposite side to the upper surface, and a circumferential side surface connecting the upper surface and the lower surface to each other. A first ridgeline at which the upper surface and the circumferential side surface intersect each other includes major cutting edges and wiper cutting edges which are alternately disposed one by one, and corners each disposed between each of the major cutting edges and each of the wiper cutting edges. A distance between the corners that are adjacent to each other is equal to or less than 60% of a diameter of an inscribed circle of the first ridgeline. The corner that is positioned at one end of the wiper cutting edge is formed at a deburring cutting edge that intersects the wiper cutting edge at an angle smaller than an angle formed by the major cutting edge and the wiper cutting edge. The corner that is positioned at the other end of the wiper cutting edge is formed at a corner cutting edge having a curvature larger than that of the wiper cutting edge.

Provided is a cutting insert, within which a burr being generated at an outer edge of a finished surface is inhibited and chipping of the cutting insert is inhibited even when the cutting insert is formed to have multiple corners superior in economical efficiency. The cutting insert has an upper surface, a lower surface on an opposite side to the upper surface, and a circumferential side surface connecting the upper surface and the lower surface to each other. A first ridgeline at which the upper surface and the circumferential side surface intersect each other includes major cutting edges and wiper cutting edges which are alternately disposed one by one, and corners each disposed between each of the major cutting edges and each of the wiper cutting edges. A distance between the corners that are adjacent to each other is equal to or less than 60% of a diameter of an inscribed circle of the first ridgeline. The corner that is positioned at one end of the wiper cutting edge is formed at a deburring cutting edge that intersects the wiper cutting edge at an angle smaller than an angle formed by the major cutting edge and the wiper cutting edge. The corner that is positioned at the other end of the wiper cutting edge is formed at a corner cutting edge having a curvature larger than that of the wiper cutting edge.