Clamp for numerical control machine tool

The clamp for the numerical control machine tool comprises a base fixed to the machine tool through bolts, a bottom plate is arranged at the top of the base, a rectangular cylinder I is arranged at the top of the bottom plate, a rectangular cylinder II is arranged in the rectangular cylinder I, and a pressing plate located above the rectangular cylinder I is arranged at the top end of the rectangular cylinder II. Wherein the bottom of the pressing plate is provided with a screw tube located in the rectangular barrel I, a screw rod is connected in the screw tube in a threaded mode, the screw rod is connected with a motor at the bottom of the bottom plate, the screw tube and the screw rod are sleeved with a spring, the two ends of the spring are fixedly connected with the bottom plate and the end face of the pressing plate respectively, and the bottom of the bottom plate is further provided with a groove for containing the motor. A ventilation channel communicated with the outer side of the base is formed in th