Idler Pulleys Information

Idler pulleyIdler pulleys are used to take up slack, change the direction of transmission, or provide clutching action. Idler pulleys are rollers that do not produce any mechanical advantage, nor transmit power to a shaft. Idler pulleys are used to lead a chain around a bend or to take up slack in a drive chain. There are many types of idler pulleys. Examples include an industrial idler pulley and a metric idler pulley. An industrial idler pulley is a pulley on a shaft that rests on or presses against a drive belt to guide it or take up slack. A metric idler pulley is a pulley system that helps in connecting to distant points through an idler pulley. Idler pulleys are produced in a variety of styles such as, V-belt, plain, flat, and cable style. V-belt idler pulleys are designed for strength and durability. The use of radial supporting ribs provides additional belt support and prevents groove deformation. Single flange idler pulleys are designed specifically for use on conveyor corners but can be used for a variety of applications. Flat belt idler pulleys have a molded-in crown that helps to center the belt and prevent rubbing against flanges. Round belt idler pulleys are designed for use with Fenner urethane belts, ropes, or cables. Other idler pulleys are commonly available.


Idler pulleys are produced with a variety of specifications. Idler pulleys are available with precision, pre-lubricated ABEC-1 ball bearings for high-speed demands. The deep uninterrupted groove provides continuous support and eliminates any binding or wedging problems. Industries manufacture idler pulleys in four product designs using three bearing types. The product designs are stamped, molded polymer, split formed, and machined. By using stamped halves surrounding a bearing, they offer an economical pulley for high-volume applications. While the standard idlers are molded in 6/6 nylon with glass reinforcement, other polymers on a made-to-order (MTO) basis are also available. Split-formed idler pulleys are available with either a replaceable or non-replaceable bearing. Due to their low tooling cost, fully machined idlers can be the economical answer when the volume usage is low and/or the pulley is complex. Some idler pulleys with advanced specifications include flat idlers from 2 in. to 6 3/4 in. overall diameter and V idler pulleys  from 2 5/8 in. to 7 in. overall diameter. Idler pulleys can be designed and manufactured to meet most industry specifications.


Idler pulleys are used in many applications. Examples include their use in numerous material handling processes. Idler pulleys are ideal hoisting equipment. Idler pulleys can be used to improve belt drive performance. Idlers can be used to reduce belt vibration by supporting a segment of belt that is prone to vibration/oscillation. Idler pulleys are used in car engines for positive clutching action by running the idler pulley on the slack side of the flat-belt drive from engine to transmission. V-belt and flat belt idler pulleys are used in transmission and power transmission systems. Idler pulleys must adhere to Conveyor Equipment Manufacturers Association (CEMA) standards.

Additional Information

Engineering360—V-Belt Pulleys Information

Engineering360—Belts and Pulleys

Engineering360—Conveyor Belt Roller and Pulley Failures

Engineering360—Pulleys and Linear Travel Calculation

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