Abstract: A milling tool includes a reversible cutter insert with a central opening having two pairs of cutting surfaces and edges. A pair of planar locating shoulders are disposed on each side of the insert, and each shoulder extends between the insert side face and an adjacent one of the cutting surfaces. The plane of each locating shoulder is at an angle to and intersects the longitudinal axis of the insert central opening. A cutter holder has a slot receiving the cutter insert with a pair of planar locating surfaces oriented at the same angle as the insert locating shoulder plane. The holder locating surfaces are abutted with and contact the insert locating shoulders to support the insert and permit one of the pair of insert cutting surfaces and edges extending out of the slot to cut a workpiece.