Cutting insert and indexable face mill

A single-sided, indexable face mill cutting insert, comprising:

• a top face having a polygonal shape and a rake surface (2);
• a bottom face opposite the top face, the bottom face having a seat surface (3);
• main flank surfaces (4a) having positive relief angles provided on substantially flat side faces extending from the top face towards the bottom face;
• major cutting edges (5a) formed between the top face and the main flank faces (4a);
• vertex angle portions formed at corners of the cutting insert and connecting the top face to the bottom face;
• pairs of sub-flank surfaces (4b) provided at the vertex angle portions and extending from the top face towards the bottom face;
• pairs of minor cutting edges (5b) formed between the top face and the pairs of sub-flank surfaces (4b);
• vertex flank surfaces (4c) provided at corners of the cutting insert at the vertex angle portions between the pairs of sub-flank surfaces (4b), the vertex flank surfaces (4c) extending from the top face to the bottom face and having an outwardly projecting curved shape;
• boundary lines (6a) formed between each vertex flank surface (4c) and each member of a pair of sub-flank surfaces (4b), the boundary lines (6a) being parallel to each other and extending from the top face towards the bottom face;
• and
• wherein:
• the vertex flank surfaces (4c) are smoothly connected with the sub-flank surfaces (4b) in a tangential direction, and extend along a thickness of the cutting insert in a direction along a vertex angle bisector line (B);
• and
• second curved ridges (5c) formed at an intersection of the vertex flank surfaces (4c) and the rake surface (2) have substantially the same shape as first curved ridges formed at an intersection of the vertex flank surfaces (4c) and the seat surface (3).