What Is an Idler Sprocket?

An idler sprocket is a device used to keep the tension in a chain or chain drive system. Often comprising nothing more than a sprocket installed on a springtime tensioned arm, the idler sprocket pulls against the chain in a continuous way to keep the chain tight all the time. How big is the sprocket found in an idler sprocket assembly has no influence on the overall performance of the chain get; however; a larger sprocket will often last longer because of the slower quickness of the sprocket, which saves use on the sprocket’s bearings. Maintenance for the idler assembly is commonly no more than an occasional greasing of the sprocket’s bearings.

When driving a machine by chain, the tension of the chain should be kept at a continuous to avoid the chain approaching off of the drive sprockets. By installing an idler sprocket in the drive program, the chain is usually kept taut without being over-tightened. Working a chain in an over-tight condition can lead to premature bearing and chain failure while an idler sprocket placed in the machine is usually a way to greatly lengthen the life of the chain, sprockets and the bearings on the machine’s sprocket shafts.

The ideal installing the idler sprocket is on the opposite side of the chain between your drive sprocket and the driven sprocket. The application should place the idler sprocket in a position which has the sprocket pushing or pulling the chain towards itself as it loops the two major sprockets in a shape similar to the letter B. This design allows the pulleys to draw the chain hard without hindering the idler at all as the drive chain passes over the sprocket. If a condition presents itself which needs the get to exert surplus pressure on the drive chain, the idler will flex against the chain, allowing it to expand while remaining in touch with the get sprockets.

While the vast majority of idler sprockets are manufactured of steel, many materials are accustomed to manufacture an idler sprocket. Many poly or composite sprockets have been used in combination with great success and some wooden sprockets are also used on some machinery without concern. Many machines, so that they can reduce the put on on the drive chain, use an light weight aluminum, cast iron or steel sprocket coated in a nylon material. The metallic hub enables the idler sprocket to remain very strong while the nylon covering can be mild on the chain links.


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