Abstract: A grinding wheel contains two ring-shaped flanks and is axially displaceable by an axial drive. A radial slide is radially adjustably displaceable relative to the grinding wheel by a radial drive. Both of the displacements in axial and radial direction can be measured by a respective displacement path measuring device. Two dressing tools can be independently reciprocatingly displaced between an operative position and a wear measuring position at the radial slide. A wear measuring device is arranged at the radial slide for measuring in a direction extending substantially parallel to the grinding wheel axis the wear of the dressing tools. The relative displacement in the direction of the grinding wheel axis is governed by the desired flank profile, and a control increases such relative displacement in the direction of the grinding wheel axis by the amount of the wear of the dressing tools.