Abstract: An impeller for an axial fan, this impeller comprising a hub transversally split into two parts each defining recesses into root portions of a plurality of impeller blades are inserted and locked by means of key-pieces when the two parts are joined together. Each key-piece has two spaced projections on one side for engaging two corresponding recesses diametrically located in the end surface of the root of each impeller blade close to the periphery of this end surface, and two equally spaced projections on its other side for engaging two corresponding recesses provided in the bottom surface of the recess in the hub. These pairs of projections on both sides of the key-piece which is preferably ring-shaped, are advantageously shifted from a certain angle along the circumference of the ring. The amount of angular displacement of the projections can be determined by mere adjustment of the mold in which the key-pieces are produced.