A throwaway carbide indexable insert and associated tool are disclosed with a flat body (2) that has as base a flat supporting surface (3), as well as at least two cutting edges (4, 5) at the side (6) opposite to the supporting surface (3). The essential characteristic of the invention is that the body (2) is square-shaped and that at least one major cutting portion (4a) and at least one minor cutting portion (5a) are provided. The cutting edges (4, 5) of the major cutting portion (4a) and of the minor cutting portion (5a) are inclined in opposite directions in relation to the supporting surface (3). The flank (8) of the major cutting edge (4a) is perpendicular to the supporting surface (3) and the flank (9) of the minor cutting edge (5a) falls back therefrom inclined at an angle with the supporting surface (3).
