A fast-action harrow-disc coupling for fixing a harrow disc (1) to the corresponding hub (2), which is characterized in that it consists of a planet wheel (4) fixed to the corresponding hub (2), the planet wheel (4) being provided on its front face and centrally with a frustoconical projection (5) having a polygonal base, with a section of a threaded shank (6) protruding centrally from the frustoconical projection (5)； it being envisaged that the corresponding disc (1) is provided with a central hole (7) for positioning the polygonal base of the frustoconical projection (5), the disc (1) being fixed by means of the thread of a nut (12) onto the section of the shank (6) corresponding to the frustoconical projection (5), with the arrangement, in between, of a plate (9) having a cavity (10) with a central hole (11) for positioning the frustoconical projection (5) and allowing passing out of threaded shank (6), respectively.
