The screw is a tool to tighten the machine parts step by step by using the physical and mathematical principles of the oblique circular rotation and friction of the object. Screw is a general term for fasteners, which is spoken daily. Screws are indispensable industrial necessities in daily life: minimal screws used in cameras, glasses, clocks and watches, electronics, general screws used in TV, electrical products, musical instruments and furniture, large screws and nuts used in engineering, construction and bridges, and transportation equipment, aircraft, trams, automobiles, etc. Use both large and small screws. The screw has an important task in industry. As long as there is industry on the earth, the function of the screw will always be important. Screw is a common invention in people's production and life for thousands of years. According to the application field, it is the first invention of human beings.