Abstract: A capping machine for capping a container having a screw-threaded neck portion with a correspondingly screw-threaded cap. The machine comprises retaining means for retaining such a container in a retaining position and a rotary chuck for holding such a cap above the capping position, forward and reverse rotary drive means coupled to the chuck for rotating such a cap in both a clockwise sense and an anticlockwise sense, rotary movement monitoring means constructed and positioned to monitor rotation of the chuck, linear motion means coupled to the chuck to move the chuck both downwardly and upwardly, screwthread-disengagement monitoring means arranged to monitor when the screwthreads of such a cap and neck disengage momentarily as the cap is rotated in the unscrewing sense on the neck and the linear motion means urge the chuck downwardly, and control means connected to the rotary drive means, the rotary movement monitoring means, and the screwthread-disengagement monitoring means.