Eccentric turning in symmetrical three jaws clutch: I solved the problem with off-center turning in the 3-jaw clutch by the usage of a underlay.
Underlay is piece of steel plate. The thickness of the underlay defines distance between axis. Underlay was fixed on the workpiece using drop of glue. When inserting workpiece to the clutch, the underlay must lay on the jaw as seen at the picture:
Method is working!