In metal cutting processes, an effective control system, which depends on a suitably developed scheme or set of algorithms can maintain machine tools in good condition. In this paper, an approach is developed for cutting force control of CNC machine. Several linear models are identified based on different working conditions. A dominant model plus uncertain terms is derived from these model set, to yield the necessary and key information from the system. Subsequently, it is used as a state estimator, and robust control is carried out by using the observed variables and cutting force. The developed approach is applied to a milling machine center. Examples taken from experimental tests shown that the developed approach is effective for the uncertain CNC machine.