An idler sprocket is a device used to keep the tension in a chain or chain get system. Often comprising nothing more than a sprocket mounted on a springtime tensioned arm, the idler sprocket pulls against the chain in a constant manner to keep carefully the chain restricted at all times. How big is the sprocket used in an idler sprocket assembly has no influence on the functionality of the chain get; however; a larger sprocket will often last longer due to the slower velocity of the sprocket, which saves wear on the sprocket’s bearings. Maintenance for the idler assembly is often no more than an occasional greasing of the sprocket’s bearings.
When driving a machine simply by chain, the strain of the chain must be held at a continuous in order to avoid the chain approaching from the drive sprockets. By setting up an idler sprocket in the drive program, the chain is normally kept taut while not being over-tightened. Operating a chain within an over-restricted condition can lead to premature bearing and chain failing while an idler sprocket placed in the system is usually 
a method to greatly prolong the life span of the chain, sprockets and the bearings on the machine’s sprocket shafts.
The ideal installing the idler sprocket is on the contrary side of the chain between the travel sprocket and the driven sprocket. The application should place the idler sprocket ready that has the sprocket pushing or pulling the chain towards itself as it loops both principal sprockets in a form like the letter B. This design will allow the pulleys to pull the chain hard without hindering the idler at all as the drive chain passes over the sprocket. If a condition occurs which needs the drive to exert extra strain on the drive chain, the idler will flex against the chain, and can expand while staying in touch with the get sprockets.
While the vast majority of idler sprockets are manufactured of steel, many components are used to manufacture an idler sprocket. Many poly or composite sprockets have already been used with great achievement and some wooden sprockets are also used on some machinery without concern. Many machines, so that they can reduce the use on the drive chain, use an aluminum, cast iron or metal sprocket coated in a nylon materials. The metallic hub allows the idler sprocket to remain very strong while the nylon covering is usually mild on the chain links.