Roller chain or bush roller chain is the type of chain drive most widely used for mechanical power transmission on many forms of domestic, commercial, and agricultural machinery, including conveyors, wire and tube drawing machines, printing presses, cars, motorcycles, and bikes. It consists of a set of small cylindrical rolls held sideways. It is operated by a toothed sprocket axle. It is a easy, reliable, and efficient means of transmitting power.
The design of the roller chain reduces friction when compared to simpler designs, resulting in greater efficiency and less wear. There were no rollers and bushings in the original power transmission chain types, with both the inner and outer plates supported by pins that touched the sprocket teeth directly; however, this design revealed extremely rapid wear of both the sprocket teeth and the plates as they rotated on the pins. The development of bushed chains partially solved this problem, with the pins holding the outer plates going through bushings or sleeves connecting the inner plates. It spread wear over a wider area; however, the sprocket teeth were still wearing faster than appropriate from the slipping friction against the bushings. Adding rollers surrounding the chain's bushing sleeves and providing rolling contact with the sprocket teeth resulted in excellent wear resistance of both sprockets and chain as well.
The roller chains are produced in many sizes, the most common American National Standards Institute (ANSI) standards being 40, 50, 60, 80. The first digits show the chain pitch in eighths of an inch, the last digit being 0 for the regular chain, 1 for the lightweight chain and 5 for the bushed chain without rollers. Therefore, a half-inch pitch chain would be # 40 while a # 160 sprocket would have the teeth spaced two inches apart, etc. Metric pitches are measured in sixteenths of an inch; hence an ANSI # 40 would be equal to a metric # 8 chain (08B-1). Most roller chains are made of plain carbon or alloy steel, but in food processing machinery or other places where lubrication is an issue, stainless steel is used and nylon or brass is occasionally seen for the same reason.
Usually the roller chain is hooked up using a master link, which usually has one pin held by a horseshoe clip rather than a friction fit, allowing it to be inserted or removed with simple instruments. Chain with removable link or pin is also known as cottered chain, which allows adjustment of the length of the chain. Half links are available, and use a single roller to increase the chain length. Riveted roller chain has "riveted" or crushed on the ends of the master link. These pins are not removable and are made to be durable.