The present invention relates to a milling cutter (200) comprising an insert pocket (201) and a cutting insert (100) mounted in the insert pocket (201) by means of a clamping screw (210); the cutting insert (100) having a shape having an upper face (150) and a lower face (160) being opposite to each other, two longitudinal side faces (110, 120), and two transversal side faces (130, 140) connecting the upper face (150) and the lower face (160), with a through hole (190) passing through each central part of the upper face (150) and the lower face (160), wherein
the longitudinal side faces (110, 120) are opposite to each other, and normal to the upper face (150) and the lower face (160);
the transversal side faces (130, 140) are opposite to each other, and normal to the upper face (150) and the lower face (160);
each of the upper face (150) and the lower face (160) is provided with two chip discharge grooves (153, 154) extended along both transversal side faces (130, 140), the two chip discharge grooves (153, 154) are inclined oppositely in the transverse direction so that each of the upper face (150) and the lower face (160) is provided with two corner cutting edges (150-1, 150-2) at diagonally opposite corners,
the longitudinal length of the cutting insert (100) is longer than the transversal length of the cutting insert (100);
wherein the cutting insert (100) is mounted in the pocket (201) such that the two longitudinal side faces (110, 120) are disposed in the axial direction of the cutter (200) and the two transversal side faces (130, 140) are disposed in the radial direction of the cutter (200); and one longitudinal side face (120) and one transversal side face (130) acts as the corner cutting edge.