Abstract: A shaft of a high-speed AC dynamoelectric machine includes axially directed flutes which define lands upon which an aligned stack of annular laminations of magnetic steel are shrunk-fit. The flutes concentrate contact forces generated by shrink-fitting in known positions and the non-contacting regions aligned with the flutes provide a small amount of resilience which permits thermal expansion of the rotor to occur without forcing a migration in the shrunk-fit contacting surfaces. The flutes may be used as axial ventilation holes whose effectiveness is enhanced by radially directed air flow channels communicating between the flutes and the outer surface of the rotor. In rotors using laminations which include keyways therein, the fluted shaft provides sufficient keying of the lamination to the shaft so that a key may be omitted.