may be employed for example for mounting a video disc and the centring surfaces 65c for mounting an audio disc assuming that the video disc has a larger centre hole than the audio disc in either case the disc can be mounted or removed in the release position of the centring members 65 fig8 shows a disc 29 39 which is centred and clamped by means of the centring surfaces 65c the disc 29 39 rests on the limbs 73 of the centring members 65 which each have a supporting surface 107 the supporting surfaces 107 together functioning as the disc alignment means in the present embodiment the sliding bush 75 and hence the centring members 65 are moved by an axial displacement of the two projections 105 this displacement is obtained by a rotation of two actuating rings relative to each other namely a first actuating ring 109 and a second actuating ring 111 the second actuating ring 111 forms part of the cylindrical element 67 and is therefore rigidly connected to the drive spindle 57 the first actuating ring 109 is mounted for rotation around the cylindrical element 67 and is axially retained at a side 109a by means of a retaining ring 113 which is secured to the element 67 if desired it may also be retained at the other side 109b the two said projections 105 are urged against the side 109b of the first ring 109 by a helical spring 79 which acts on the sliding bush 75 the side 109b of the first ring 109 has two helical cam profiles 115 which each extend over roughly one half of the circumference when the first ring 109 is rotated relative to the second ring 111.