A cutting insert for use in a peripheral rotary milling cutter having a cylindrical holder and having a side cutting edge (27) defined between a cutting rake surface (22) and a side relief flank (26) and a side base edge (23a) defined between said side relief flank and a base surface, the side relief flank comprising first and second component side relief flank surfaces (31', 31") intersecting at an intersection line (32), extending along the side relief flank from a first position (33') adjacent a leading end of the insert and located at an intermediate position thereof to a second position (33") intersecting the said cutting edge and adjacent a trailing end of the insert, the component flank surfaces being substantially planar and being angularly disposed with respect to one another so that an insert side relief angle ( gamma A) as defined with respect to the cylindrical holder in the region of the leading end substantially equals an insert side relief angle ( gamma B) in the region of the trailing end.
