During turning operations, the workpiece clamping system and the selection of the cutting conditions are of prime importance. They both have a significant influence on workpiece roundness error E-R, due to the dynamic behaviour of the chuck-axis-workpiece system. This dynamic behaviour is conditioned by selected machining parameters (cutting speed v, depth-of-cut d, feed rate f) and the design of the workpiece (length L and diameter phi). The main aim of the work was to evaluate the influence of the aforementioned parameters (v, d, f, L/phi) on workpiece roundness error E-R during turning AISI-1045 steel material, for a range of machining conditions (v=150, 200, 250 m/min,f=0.15, 0.20, 0.25 mm/rev, d=l, 2, 3 mm). Furthermore, the cutting force signals were monitored throughout the tests in order to control the process and the correlation of the three force components (depth Fd, tangential F1, feed Ff) with workpiece roundness error E-R was analysed. Of all the various operating process parameters that were evaluated, the machined workpiece length L and the depth-of-cut d were shown to have the most significant influence on E-R variation. The highest E-R values were obtained when the highest depth-of-cut d, feed rate f, cutting speed v and length L values were employed and combined. Little effect on the output measure E-R was observed when cutting speed v and feed rate f parameters were individually increased. Moreover, an increase in the cutting force (Fd, Ft, y Ff) values showed to produce a significant increase in workpiece roundness error E-R.