A composite milling cutter includes a rotatable adapter plate and ring cutter. The adapter plate has a raised key portion with a peripheral side wall having a plurality of curved abutment surfaces symmetrically located on an inscribed circle, ICAP defined by the raised key portion. The cutter ring has an opening with a peripheral side wall for receiving the raised key portion of the adapter plate. The peripheral side wall has a plurality of curved abutment surfaces complimentary in shape to the curved abutment surfaces of the adapter plate and symmetrically located on an inscribed circle, ICCR, defined by the opening. A tolerance between the abutment surfaces of the peripheral side wall of the raised key portion and the abutment surfaces of the peripheral wall of the opening is such that run-out is minimized.