The virtual copy milling system has been developed. In the virtual copy milling system, a stylus and a master model in copy milling are defined as geometrical surface models, and the stylus motion corresponding to the tool motion is simulated by applying copy milling principle. This method is simple enough to generate the tool motion in real time, and experimental cutting have been succeeded to show NC programless milling of sculptured surface. The real time tool path generation is indispensable for the adaptation of cutting conditions such as depth of cut and feed speed to maintain stable machining. In this study, the machining strategy for the adaptation of cutting conditions is proposed to realize an autonomous NC machine tool.