Machine Design

Tolerance Rings Do Double Duty as Shims or Slip Clutches

Tolerance rings can be used to mount ball bearings in molded plastic housings. They are corrugated steel fasteners that act like elastic shims in that waves on the ring are radial springs. The rings handle typical problems associated with mounting ball bearings in plastic housings, such as cavity-to-cavity variations and thermal growth. They may be used in place of adhesives or elastomer boots, say company officials.

What many designers may not know is that tolerance rings can also act as torque-limiting (slip clutch) mechanisms to protect expensive components from excessive torque. The devices help prevent failure and costly repairs. The range of slip can be adjusted in units of lb-ft or lb-in. and common applications include automotive and power-tool components.

Automotive slip-clutch applications include:

•Gear mounts in electronic power-assisted steering units
•Mechanical seat-height adjusters for passenger cars
•Antitheft devices for steering columns

Power-tool applications for tolerance rings include:

•Bevel-gear mounts in angle grinders
•Allowing a slip between the rotor and blades of a hedge trimmer

This information supplied by USA Tolerance Rings, West Trenton, N.J.
For more information, Circle 623.

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