CNC (computer numerical control) machining fourth shaft fixture

The utility model discloses a CNC (computer numerical control) machining fourth shaft fixture. The CNC machining fourth shaft fixture comprises a body, a harmonic speed reducer, a servo motor, a coding device, a tool fixture and a controller, wherein the harmonic speed reducer comprises a waveform generator, a flexible wheel and a steel wheel; the waveform generator is inserted in the flexible wheel; the steel wheel sleeves the flexible wheel in a meshed manner; a power output shaft of the servo motor is fixedly connected with the waveform generator of the harmonic speed reducer; and the steel wheel of the harmonic speed reducer is fixedly connected with the body; the flexible wheel of the harmonic speed reducer is fixedly connected with the tool fixture; the tool fixture is provided with a fixing device for positioning a product; the coding device is arranged on the servo motor and is electrically connected with the controller; and the controller controls operation of the servo motor. The CNC machining fourth shaft fixture is low in noise and high in rigidity; when the CNC machining fourth shaft fixture is electrified after power is cut off, the CNC machining fourth shaft fixture is not required to be aligned again in the original point, and can continue to work; and the machining efficiency and the machining precision are high.