Abstract: A method and an apparatus for controlling spindle speed are disclosed. When the speed ranges of respective gear ranges are selected in advance so that speed ranges corresponding to neighboring gear ranges partially overlap one another, and the gear range conforming to the commanded spindle speed is selected for rotating the spindle at the commanded spindle speed, it is determined whether the commanded spindle speed belongs to the currently selected range, no gear change is made if the decision is affirmative, and the gear range to which the newly commanded spindle speed belongs is found if the decision is negative, the gear range being switched to the gear range thus found.

Abstract: A numerical control device 102, in which a processor 102a numerically controls a machine tool 103, is provided with an external storage unit 201 for storing machining data conforming to various shape patterns, input means 202, an editing processor 102c and an internal memory 102d, in order to implement a function for the creation of numerical control information. Machining data, corresponding to a part code entered from the input means 202, is read out of the external storage unit 201c. The editing processor 102c creates numerical control information, which is stored in the internal memory, from the machining data and, e.g., numerical values input from the input means 202.

Abstract: A system for preparing numerical control information wherein data necessary for machining is divided into several items and then entered, item-by-item, in accordance with certain rules, in an apparatus for preparing numerical control information. The apparatus responds by executing predetermined arithmetic and editing operations to prepare the numerical control information. To input the data, language and graphics readily understandable by one who can prepare or comprehend an ordinary blueprint are displayed on a display screen provided on the apparatus, the display using ordinary characters and symbols to request that the operator enter the required data. The operator responds to the request by using ordinary numerals, characters and symbols to enter the required data in the apparatus for preparing the numerical control information.