Pulley flanges are the appropriate method of belt tracking for most timing belt drive and conveying systems. Flanges retain the belt on the pulley by resisting lateral forces that pull the belt to one side or the other. Flanges are attached to the pulleys by a rolling process or fastened with screws depending on tooth profile and pulley diameter. Small and medium pitch pulleys up to approximately 250 mm in diameter are usually supplied with rolled on flanges. Large pitch pulleys such as T20, AT20, and XH, are commonly supplied with screwed on flanges.
For general recommendations concerning where to use flanges, please see the illustrations below.
Pulley Tracking with Flanges:
Flanges can be used on one pulley only for systems with close center-to-center distances
Flanges on back side idlers can be used to track belts when flanges on the tooth pulleys are not an option. Always locate the idler on the slack side of the belt towards the return pulley as shown
For reversing applications, locate the idler between the pulleys.