6. A method of operating a numerical control unit that is responsive to an instructed feedrate for controlling a machine tool to move along a selected one of linear axes in a spatial coordinate system and rotate about a selected one of said linear axes, said selected one of said linear axes thereby becoming an axis of rotation, said numerical control unit being operative to automatically machine a workpiece, said method comprising the steps of: determining whether a machining mode is a linear interpolation mode; determining whether a move command is for two-axis simultaneous movement with respect to said selected one of said linear axes and said axis of rotation if said machining mode is a linear interpolation mode; determining an angular and radial position of said tool with respect to said axis of rotation about which said machine tool is to rotate if said move command is for two-axis simultaneous movement; and correcting said instructed feedrate according to said angular and radial position so that the actual feedrate is equal to the desired relative speed between the tool and workpiece.
7. The method of operating a numerical control unit as set forth in claim 6, wherein said machining is performed in response to a single programmed block.