There is provided a disc unit for mounting a plurality of discs to an outer end of a mouldboard of a grader. The disc unit includes a mounting bracket for securing to a rear face of an outer end portion of the mouldboard. A frame is pivotally mounted on the mounting bracket and supports an axle which mounts the discs thereon. A hydraulic cylinder pivots the frame supporting the discs in relation to the mounting bracket for raising and lowering the discs to engage the ground at various depths of cut. A cushion valve releases the hydraulic cylinder in the case of an obstruction engaging the discs. The discs include a concave inner surface which are arranged to face towards the grader and partially in the direction of travel for urging particulate material away from the shoulder and towards a centre of the road.
