The tailstock is used in turning operation to guide the workpiece rotation. This paper introduces an investigation for the influences of the tailstock axial force on the turning dynamics. A set of experiments were carried out to study the effect of different axial clamping force on the vibration of the tool- workpiece system and consequently on the workpiece roundness error. Vibrations generated during turning were measured in three directions (radial, axial, and tangential). Moreover, the resulted roundness errors on the workpieces surfaces were also measured. The results showed a great dependence of both vibrations existing during turning and the resulted roundness error, on the tailstock axial clamping force. The control of this force will improve the workpiece quality and detect the other errors such as chuck clamping. There is an optimum value for this force that reduces the roundness error to a minimum value. Also the vibration signals in the axial direction correlates comparatively well with the tailstock clamping force than those in other directions.