Tolerance Rings can be used to transmit torque from one cylindrical component to another, without the need for costly splines or expensive keyways. Gears, pulleys, disks, sprockets, flywheels, rollers, impellers are a sample of the many torque transmitting components that can be mounted with tolerance rings. Unlike a keyway’s tolerances which result in backlash with a change in rotational direction, the tolerance ring provides zero backlash.
Depending on the diameter of the mounting components and the configuration of the tolerance ring, torques from .015 ft.-lbs. to 175 ft.-lbs. and much higher can be handled prior to slippage. The amount of torque transmitted will vary with tolerance ring configurations, diameters, material hardness, surface finish, and the amount of thermal expansion/contraction occurring between components. The slippage can provide natural torque overload protection, acting as a "fuse" and preventing damage to less sturdy components such as plastic gear teeth.
Tolerance rings often mount ball bearing outer races to retain the bearing in thermal growth applications. Similarly, the rings can be used in high temperature applications involving dissimilar materials such as steel shafts to plastic glass filled fan hubs or impellers. Transitioning between min./max. temperature conditions, the plastic hub will expand and contract at a different rate than the steel shaft. The tolerance ring’s waves will compensate for these dimensional changes due to thermal fluctuations while simultaneously transferring the minimum torque.
Large radial loads can also be handled when the groove axial width is less than the axial width of the outer components and the shaft diameter prevents the tolerance ring waves from being pressed beyond their elastic limit.
When there are multiple torque components to be mounted on a common shaft, knurls can present assembly challenges and set screws may loosen over time. Knurling the shaft in advance won’t work since the middle components won’t be able to slide past the first knurl during assembly. Adding the next knurl after each disk is in place is costly. Keying or press fitting onto a stepped shaft is expensive and calls for components with different bore diameters.
Grooving the shaft and placing BN style tolerance rings allow for both economical and ease of assembly. Tolerance rings enable the clearance between the disk’s ID and the shaft’s OD to increase, thus eliminating the “snagging” or the cumbersome “walking” components down a long rod or tube. The shaft’s OD tolerances can also be relaxed with press fit assembly. If no torque hold is needed and tolerances are held tight, the assembly can often be done by hand without the need of presses.
Rather than using a solid roller that can add weight as well as cost, tolerance rings on the inside diameter (ID) and outside diameter (OD) sandwich an inexpensive alloy spacer to transfer torque from the inner spindle to the outer roller or pulley shell.
Tolerance rings allow for easy rotational alignment of indicator knobs and dials during initial calibration, especially with electronic instrumentation. For electronic equipment that needs “tuning” prior to the placement of control knobs or dials, tolerance rings allow for proper polar orientation with reference markings, numbers or letters.