Abstract: A method of grinding control edges of a control bush of a rotary slide valve for hydraulic steering of motor vehicles, includes placement of the control bush in a support in form of slide shoes or a V block and additionally securing the control bush in the support by pressure rollers. A precise angular positioning of the control bush is effected by press-fitting a mandrel into the interior of the control bush. After grinding the control bush to a predetermined outside diameter, the reference points commensurate with the angular position of the individual control edges are determined by a measuring system. Based on the determined reference points, an optimum reference point for the angular position of all control edges is computed and utilized for adjusting the mandrel in form of a zero point shift for grinding the control edges.