This paper shows how a low cost personal computer, Sinclair ZX Spectrum, may be used in a high technology and sophisticated application, such as a Computer Numerical Control (CNC) system for a lathe. The paper describes the set of ‘user friendly’ software modules that have been developed for both pre- and post-processing operation. Software modules for preprocessing enable the user to define a new job, and save it after editing. Post-processing modules perform interpolation and auxilliary functions, as well as execute the job. Hardware development includes stepping motor drives for carriage and croos-slides. It also includes an I/O expander module for interfacing the stepping motor drives to ZX Spectrum.