Abstract: When round screw thread machining is performed with a tool (TL) having a radius smaller than a circular arc radius of a threaded portion (RST), data necessary for deciding (i) tool path patterns of round screw threading cycles (PLi) and (ii) a starting point (Pi) of each round screw threading cycle are commanded and incorporated in NC command data of the round screw threading cycles, the cycle starting point (Pi) of each round screw threading cycle (PLi) is obtained along the circular arc profile of the round screw thread using the data, and round screw thread machining is performed by repeatedly executing the threading cycles while successively shifting the cycle starting point.

Abstract: A tool compensation method for cutting a surface on a workpiece having a slanted surface. A radius at a final point is determined by a path computing unit using coordinates of the final cutting point and a tool height. Based on these values thus determined, coordinates of a final offset position, which is aligned with a tool center, is also computed. Corrective values in the directions of the X and Y axes are determined using the computed coordinates and coordinates of a starting offset position, to thereby correct the movement of the tool center.

Abstract: In a numerical control machine tool, the time that the tool or bit actually operates is counted in the control device of the numerical control system. The present time control data collection system comprises a data memory having a plurality of flags, the condition of each of which reflects the actual operation of the related tool or bit, a real time clock which provides signals at predetermined intervals, and means for counting the real time clock on the condition that the particular flag in said memory is on. The counted value is displayed either directly, or the fact that the counted value exceeds the predetermined reference value is indicated. The present system can also be implemented using a programmed micro-computer.