a disk player in which a clamping member clamps a disk against a turntable . the clamping member has two annular bosses and the turntable has one annular boss located between those of the clamping member . a projection of the clamping member has a projection that fits within a slightly larger recess in the turntable . a ball bearing in the projection moves towards the turntable and forces radially outwardly three ball bearings which then contact the side walls of the recess .