An impeller device (10) for centrifugal fans (1), having comprising a center wheel (40), at least one side disc (20, 30) and fan blades (50). The center wheel (40) and the side disc(s) (20, 30) are equipped with attachment devices (24, 44) for attaching the blades and the center wheel's (40) attachment device (44) comprises a protrusion (45) extending substantially in the center wheel's radial direction and arranged to abut against the second side end (54) in the fan blades (50).