In this article the causes of elastic deformations of the MFTW (machine tools, jig-fixture, cutting tool and workpiece) system and their influence on diameter obtained after turning operations using lathe machines have been investigated. The major contributing causes on this issue, such as machine tool spindle bearing elastic system, radial deformation of spindle shaft as well as the deformation of workpiece, the influence of cutting forces and the drive system dynamics, elastic deformation of the machine tools components and more other causes are identified. An attempt has been made to model the nature of influences of the above mentioned causes in an example of lathe machines. Also a simple methodology for categorising lathes in a machine shop depending upon their level of accuracies of machined products is briefly proposed. This methodology may be useful for machine shop supervisors and process design engineers to reduce the rate of machining defects for a shop floor yielding higher productivity. This work may perfectly suit the activities of manufacturing engineers handling shop floor scheduling.