The screw is a tool that uses the physical and mathematical principles of circular rotation and friction of the inclined plane of the object to tighten the object gradually. Screw is a common term for fasteners, everyday slang. Screws are indispensable industrial necessities in daily life: such as cameras, glasses, clocks, electronics and other small screws; General screws for television, electrical products, Musical Instruments, furniture, etc.; As for engineering, construction, Bridges use large screws, nuts; Transportation appliances, airplanes, trams, cars, and so on, are large and small s