Tolerance Rings cut noise and vibration
Machine Design ran a good article on how tolerance rings reduce noise in appliance design. Click here to check it out. If you have never heard of tolerance rings you are not alone but they are extremely useful. I used tolerance rings to mount timing belt sprockets to the output shaft of a small electric motor. The primary benefit was that the bore of the sprocket did not have to be machined to a close tolerance because the tolerance ring took up the variation in the bores. Click here for some details on the design.
Tolerance rings are used primarily to mount bearings in repair situations. Again the tolerance rings allow bearings to be mounted in repaired bores that may not be held to a tight tolerance. At one time General Motors mounted timing belt pulleys to cam shafts. For more details on the use of tolerance rings click here.