The invention relates to a harrow disc fixing mechanism for fixing a harrow disc (1) to a hub (2) provided on the main frame of the harrow and having a planet wheel (3) solidly connected thereto. According to the invention, the planet wheel (3) is provided with a projection (5) for centering the associated disc (1) as it is being mounted on the hub (2) and the disc (1) is provided with a central and circular hole (9) for receiving the centering projection (5). The invention is characterized in that the centering projection (5) protrudes from the planet wheel (3), said projection (5) having a frustoconical form with a cylindrical base. The invention is also characterized in that the disc (1) is provided with at least three elongate holes (7) arranged concentrically with the hole (9) and having a widened end (8), intended to receive corresponding screws (6) for fixing the disc (1), whereby said screws can be screwed into corresponding nuts (10).
