Data processing device for three dimensional surface machining

A data processing device for machining a three dimensional surface includes a tool locus data generator providing tool shape and dimension indicative information of a machining tool and machining route information, calculating information selected from a curvature, a normal line and a tangential line at a machining point of the three dimensional surface, and calculating the optimum shape of a machining tool and/or controlling condition of the tool based on the calculated information; a device for checking the tool locus data of a machining tool based on a predetermined pattern; and a processor for converting the checked tool locus data into data which is to be inputted into a machine which conducts three dimensional surface machining. The machining tool to be used with the data processing device has a plurality of machining portions with various curvatures and the most suitable machining portion of the tool is selected by the data processing device in response to variations in the curvature of the three dimensional surface. Machining accuracy and efficiency are greatly improved when using the device of this invention, and various modifications are achievable to provide wide applicability.