whta is screw？？

Screws are tools that use the physics and mathematics of the beveled circular rotation of an object and friction to tighten the instrumental mechanism in a progressive manner. Screw is the generic term for fastener, the daily verbal language.

Screws are indispensable industrial necessities in daily life: such as cameras, glasses, clocks and watches, electronics, etc. use of very small screws; television, electrical products, musical instruments, furniture and other general screws;. As for engineering, construction, bridges use large screws, nuts; transportation apparatus, aircraft, trams, cars, etc. is the size of screws and use.

Screws in industry has an important task, as long as the existence of industry on earth, the function of the screw will always be important. Screw is a common invention in the production life of people for thousands of years, according to the application area, it is the first human invention