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SUMMER 2014

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Distributor's Link Magazine Summer Issue 2014

26 THE DISTRIBUTOR’S

26 THE DISTRIBUTOR’S LINK Several times each year the IFI technical staff is asked why the nylon inserts in nylon insert lock nuts are ripping out of the nut bodies while being tightened. Reason: TOO MUCH INSTALLATION SPEED! Solution: Use an installation tool that does not exceed 1200 RPM. A nylon insert lock nut is a two part assembly. There is the steel nut body that has a free-running thread plus a nylon ring with an inside diameter that is smaller than the major diameter of the bolt or screw thread the nut is driven on to. The nylon ring is staked into the nut body by crimping the upper edge of the nut. The crimping secures the nylon ring in place so that the nylon ring and nut body become a single assembly. When a nylon insert lock nut is driven on to a bolt or screw the nut body screws on freely until the bolt or screw end comes in contact with the nylon ring. The nylon ring immediately creates prevailing torque as it is designed to do. Prevailing torque is the result of friction being created between the inside diameter of the nylon ring and the major diameter of the mating bolt or screw. Industrial Fasteners Institute 636 Oak Tree Blvd. • Independence Ohio 44131 Phone: 216.241.1482 • Fax: 216.241.5901 www.indfast.org IMPACT WRENCHES COMMONLY DESTROY NYLON INSERT LOCKNUTS by Joe Greenslade Director of Engineering Technology, IFI Impact wrenches normally run in the range of 5,000 to 10,000 RPM. When impact wrenches are used to install nylon insert lock nuts it is not uncommon for the nylon rings to end up part way down the bolt or screw thread far behind the nut body that proceeds freely ahead of the ring as a separate piece until it seats on the assembly component. The reason this disengagement occurs is that the nut body has no prevailing torque, but the nylon ring does have significant prevailing torque (friction). When the nut is driven at 5,000 – 10,000 RPM the nut body literally out runs the nylon ring resulting in the ring being ripped from the nut as the nut runs away from the ring. nuts. When this happens there is nothing wrong with the They are just not designed to be effectively installed at ultra-high speed. The simple solution is to use a “nutrunner” instead of an impact wrench for installing nylon insert lock nuts. Most nutrunners run at a speed of about 700 – 1200 RPM. Replace impact wrenches with nutrunners and the problem of the rings ripping out of the nylon insert lock nuts during assembly will go away.

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