There are many important mechanical parts in the power transmission such as the speed reducers, sprockets, worms, and gears, etc. Among them, couplings also play a very important part in the power transmission. Couplings have various species, types, and sizes. Therefore, in order to choose appropriate products, customers should take many aspects into consideration. In addition to the correct understanding of the species, types, sizes, they should choose the couplings according to the needs of the transmission system. First of all, they can choose from couplings that have been developed as a standard. At present, there are many kinds of standard couplings in China. Most of them are worldwide couplings. Each coupling has its own features and applications. Generally, they can fulfill the needs of a wide range of circumstances. Among so many standard couplings , the good decision of items is relevant with the performance, stability, noise, transmission efficiency, economy, serv...