In order to enable a continuous adjustment of the variable clearance space (1) of a reciprocating compressor (15), a threaded spindle drive with a threaded spindle nut (10) and a threaded spindle (9) is provided as an adjusting device (7), wherein the threaded spindle nut (10) is embodied as a plastic nut (20) with internal thread (24), the plastic nut (20) is arranged with an external thread (23) on an internal thread (22) of a nut carrier (21) of the threaded spindle nut (10), and the thread height (y) of the internal thread (22) of the nut carrier (21) and the thread height (x) of the external thread (25) of the threaded spindle (9) is respectively embodied with 50 to 80% of the radial thickness (d) of the plastic nut (20) and the plastic thickness is at least 15% of the thread pitch (z1) of the internal thread (24) at least in the region of the thread flanks (26) of the internal thread (24) of the plastic nut (20).