A CD machine gearing is arranged with a lifting core in a hollow casing, one end of the core is provided with a principal axis, the other end is provided with a mobile read head which is connected to a connecting device, a perforation is set on the side of the mobile path, a bearing fixes a screw and one end of a drive motor on lower casing by a bracket with a prescribed height at a position facing to the perforation, when the core lifting, passing through the perforation without interference, and the coupling teeth for joining the screw and the connecting device so as to turn thin.