The aim of the paper is to analyse the vibrations during a turning manufacturing process in terms of the Machine-Tool-Part unit having particularly complex dynamic characteristics. The vibratory phenomenon is influenced by many parameters like workpiece, tool overhang, cutting speed, depth of cut and feed rate. This phenomenon is not completely known yet, so the aim was to highlight its origins using two complementary approaches: numerical and experimental. Finite element calculations were carried out, in order to identify parameters which characterize vibrations in machining like structural parameters (lathe, tool holder, cutting tool, workpiece, tailstock, tool overhang ...). A design for an experiment of process parameters (depth of cut, feed and cutting speed) was used and one series of turning tests was performed. Results have shown a significant effect between these parameters on the resulting surface roughness, consumed power, cutting time and tool vibrations and a best comprehension of the process.