a triangular top surface, a triangular bottom surface, and three circumferential surfaces extending between the top surface and the bottom surface, wherein on each side of the cutting insert an individual one of the three circumferential surfaces extends along an edge of the triangular top surface and along an edge of the triangular bottom surface; and

at each of the top surface and the bottom surface three cutting corners, three main cutting edges and three minor cutting edges, wherein each cutting corner connects a main cutting edge and a minor cutting edge, wherein each of the cutting corners, each of the main cutting edges and each of the minor cutting edges are provided at an intersection between the top surface or the bottom surface and one of the circumferential surfaces, wherein each of the circumferential surfaces includes a planar contact surface, the planar contact surface being delimited by a main cutting edge at the top surface and by a main cutting edge at the bottom surface, wherein the top surface and the bottom surface have a common axis of rotational symmetry, wherein each of the circumferential surfaces has two minor clearance surfaces, wherein a first of the two minor clearance surfaces intersects the top surface at a minor cutting edge and a second of the two minor clearance surfaces intersects the bottom surface at a minor cutting edge, and wherein each of the minor clearance surfaces starting from the minor cutting edge is inclined towards the axis of rotational symmetry.