1. Classification: it can be divided into oil seal chain and non oil seal chain. The so-called oil seal chain is that there is an oil seal in the middle of the inner and outer chain pieces, which packs the lubricating oil in the middle to help the chain lubricate. Without this oil seal, it is called non oil seal chain
2. Structure: in terms of oil seal chain, it can be roughly divided into six major structures: inner chain, outer chain, pin, Bush, roller, oil seal, etc. In the manufacturing of chain, the accuracy and wear resistance of pin and bush are very important. Generally speaking, the chain is lengthened because of the wear of pin and bushing. Don't underestimate this little gap. For a chain of 100 knots, as long as each knot is stretched by 0.1mm, 100 knots add up to a centimeter longer. And when the chain starts to wear, the wear speed will rapidly become faster, so be very careful. As for the chain pin, in addition to the high machining accuracy, it must be a positive cylinder to maintain the fixed clearance with the bushing and reduce unnecessary wear. In addition, the outer layer of the pin must be plated with chromium carbide to increase the rigidity and hardness, so as to reduce wear. The hard metal is easy to be brittle, and the center must be properly heat treated to keep the center flexible. In the bushing part, the early chain bushing is formed by bending steel plate, which can reduce the cost, but in the high strength state, the joint is easy to deform and cause the rotation not smooth. In recent years, with the progress of processing technology, the bushing of high-quality chain has been processed by cold forging, and the overall durability is better.
3. Oil seal: for the oil seal chain, the traditional O-ring (O-ring) is the most common. However, it is found that the traditional O-ring will deform in the extrusion state, resulting in a larger friction area with the inner and outer chain plates, resulting in an increase in friction resistance and a decrease in life. Therefore, the world's chain manufacturers have made great efforts in the durability and friction of oil seals to develop oil seals of various shapes, so that you can see many different terms and shapes of oil seals, such as the x-xw, r-xw, UW, u and other types of oil seals of rk, Japan chain factory. Each oil seal of different shapes has different performance in durability.