Screws
A screw is a tool that uses the physical and mathematical principles of beveled circular rotation of an object and friction to tighten an instrumental mechanism in a stepwise manner. Screw is the generic term for fastener. Screws are indispensable for everyday industrial Necessities: such as cameras, glasses, clocks, electronic use of very small screws; television, electrical products, musical instruments, furniture, etc. The general screws for television, electrical products, musical instruments, furniture, etc.; as for engineering, construction, bridges, large screws, nuts; transportation apparatus, aircraft, trams, automobiles, etc. The size of the screw is used for transportation equipment, aircraft, trams, cars, etc.
Screws in industry has an important task, as long as the existence of industry on earth industry, the function of the screw will always be important. Screw is a common invention of people's production life for thousands of years, according to the field of application It is the first invention of mankind according to the field of application.