In a disc assembly for supporting a ground engaging disc on a respective support arm of a vertical tillage implement, the disc supporting hub has an annular body rotatably supported on a shaft. The outer end of the annular body is enclosed by a cap and the inner end of the annular body is enclosed by an end plate fixed on the shaft relative to which the annular body is rotated. First and second annular flanges on the inner end of the annular body receive a tongue portion of the end plate therein so as to define a sinuous, narrow clearance gap where the annular body of the hub and the end plate of the shaft are in a non-contacting, rotatable relationship with one another. The sinuous, narrow clearance gap minimizes penetration of soil and residue therethrough to the interior of the hub where bearings are located.