Ancient gears (see Chinese ancient gears) were carved with wood or forged with metal. In China's Shanxi province Yongji County Xue Jia Cliff unearthed artifacts have been bronze ratchet gears, according to textual research between Qin and Han (before the 200 BC) products. Wei Ming three years (A.D. 235) Majun invented the guide to car also used gear transmission. More than 200 years after the 16th century century, gears are mainly used for clock transmission, most of the manufacturing method is in a rotating file or milling cutter gear cutting device on the coarse gear, and then manually trimmed tooth shape. In the late 18th century, the large-size and high-precision gears needed to transmit the power were generally made of casting gears. In the 20-30 years of 19th century, the United Kingdom's J. Fox and J.G Bodemer successively studied the method of milling cast iron gears with multi-teeth forming milling cutters. In 1835, j.b Whitworth of England created the method of machining involute teeth by using hob in accordance with the principle of exhibition, but it was very difficult to manufacture the tools used mechanically to cut cast iron gears. It was not until 1854 that the American J.R Brown invented the gear milling cutter for the back, so the process of milling gears with milling cutters on universal Milling machines was popular. In the late 19th century, because the turbine, internal combustion engine and other high-speed heavy-duty machinery required the precision and productivity of gear processing, people attach importance to and develop the use of the method of machining gears, hobbing methods continue to improve. In 1897, E.R Fellows of the United States invented a disc shaper cutter to process gears by means of an exhibition method, and at the same time created a way to show a grinding shaper cutter with a large plane wheel. At the beginning of 20th century, T. Hampech of the United Kingdom studied the tooth grinding method of worm wheel. The shaving method appeared in the 20 's. The honing process began application in the late 50.