Screw is a common fastener, widely used in machinery, electrical equipment and buildings. General material is a metal or plastic, cylindrical, the surface engraved with concavoconvex groove is called threads.
Because of the different units of measurement, resulting in a variety of thread representation methods are also different. For example, m16-2x60 represents the metric thread. He means that the screw has a nominal diameter of 16MM, a tooth distance of 2MM, and a length of 60MM. For example, 1/4 -- 20x3/4 means the screw has a nominal diameter of 1/4 inch (an inch = 25.4mm). In addition, to indicate the American screw, UNC and UNF are usually added to the back of the British screw to distinguish between the United States coarse teeth or the United States fine teeth
There are many different ways of fastening thread fasteners before they are widely used. Mostly associated with carpentry and forging, rather than machining, concepts such as stitching pins and pins, wedges, tenons and tenons, nails, forging welding and binding after tying them with leather or fibers are used. Before the mid-19th century, when boat-building was fixed with split pins, bolts or rivets, there were binders, but not as many as there are in modern times.
Has always had a machine tool can be mass produced in the eighteenth century tantalum screw, tantalum screw, screws, metal screws, screw, screw became common fasteners, the technology about development in the 1760 s and 1770 s, along the way two separate process, but soon incorporates: wood screw, screw, screw (used in fixed on metal screws, wood screws, screw) is to use a single purpose machine tool processing, high yield rate, and low quantity, mould workshop production of V type thread machine screw, screw, screw, can choose a variety of different pitch.
