Abstract: A warm-up control system for a machine tool drives a spindle motor for rotating a main spindle of the machine tool before starting machining, thereby performing a warm-up operation, and acquires a spindle motor load value that is variable by heat generated during the warm-up operation. The warm-up operation is ended when the acquired spindle motor load value becomes substantially equal to a preset working reference load value. The cutting capacity of the main spindle can be improved by this warm-up operation.

Abstract: A main body of a machine tool is covered with a cover. A ceiling portion of the cover that is situated over a spindle motor is provided with an opening portion. The cover is provided with hanging portions that hang down from the opening portion with a predetermined clearance from side surfaces of the spindle motor other than the rear surface. Air that is mixed with a misty cutting fluid in a space inside the cover is sucked in through a suction pipe by a mist collector. The outside air flows into the space inside the cover through the clearance. The outside air that passes through the clearance is driven to flow through vents by a built-in cooling fan of the spindle motor, thereby cooling the motor, and is then discharged to the outside. In consequence, the temperature in the space inside the cover can never be increased by heating of the spindle motor.

Abstract: A main body of a machine tool is covered with a cover. A ceiling portion of the cover that is situated over a spindle motor is provided with an opening portion. The cover is provided with hanging portions that hang down from the opening portion with a predetermined clearance from side surfaces of the spindle motor other than the rear surface. Air that is mixed with a misty cutting fluid in a space inside the cover is sucked in through a suction pipe by a mist collector. The outside air flows into the space inside the cover through the clearance. The outside air that passes through the clearance is driven to flow through vents by a built-in cooling fan of the spindle motor, thereby cooling the motor, and is then discharged to the outside. In consequence, the temperature in the space inside the cover can never be increased by heating of the spindle motor.

Abstract: For a spring sliding on the drawbar, the coil spring is used; the removal work for keeping the inner diameters of the coil springs aligned is performed such that the clearance between the outer diameter of the drawbar and the inner diameter of the coil spring becomes a minimum; and the coil springs are caused to be guided integrally with the drawbar. By doing so, the movement of the center of gravity of the spring that is caused by repeated rotational operation of the main spindle or repeated tool clamping operation will be reduced and the amplitude by vibration will be made smaller.

Abstract: A numerically controlled machine tool performs machining by rotating a rotational tool attached to a tool holder mounted on a spindle, with keys fitted into key grooves in the tool holder. The numerically controlled machine tool includes predetermined-amount rotating unit for stopping the tool holder at a predetermined rotational position and then rotating the tool holder by a given amount, and a distance sensor which is installed apart from the tool holder and measures a distance to the outer surface of the tool holder. The predetermined-amount rotating unit stops the tool holder at a rotational position at which the key grooves do not face the distance sensor, then rotates the tool holder by the given amount. The distance sensor measures the distance to the tool holder while the tool holder is rotating. The measurement result is compared with a reference distance or distances to discriminate between normal and abnormal rotational run-out of the tool holder.

Abstract: For a spring sliding on the drawbar, the coil spring is used; the removal work for keeping the inner diameters of the coil springs aligned is performed such that the clearance between the outer diameter of the drawbar and the inner diameter of the coil spring becomes a minimum; and the coil springs are caused to be guided integrally with the drawbar. By doing so, the movement of the center of gravity of the spring that is caused by repeated rotational operation of the main spindle or repeated tool clamping operation will be reduced and the amplitude by vibration will be made smaller.

Abstract: A numerically controlled machine tool performs machining by rotating a rotational tool attached to a tool holder mounted on a spindle, with keys fitted into key grooves in the tool holder. The numerically controlled machine tool includes predetermined-amount rotating unit for stopping the tool holder at a predetermined rotational position and then rotating the tool holder by a given amount, and a distance sensor which is installed apart from the tool holder and measures a distance to the outer surface of the tool holder. The predetermined-amount rotating unit stops the tool holder at a rotational position at which the key grooves do not face the distance sensor, then rotates the tool holder by the given amount. The distance sensor measures the distance to the tool holder while the tool holder is rotating. The measurement result is compared with a reference distance or distances to discriminate between normal and abnormal rotational run-out of the tool holder.