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July 2006 edition

Spiralock threads its way through those complicated joint problems

By Daniel Cook

Some of the most advanced airframes in the world – the F-35 Joint Strike Fighter, Boeing’s 787 and NASA’s Huygens probe – have one simple innovation in common: they make use of a tougher form of female screw thread called Spiralock.

Tooling company Spiralock claims its unique thread is more resistant to stripping and loosening as it reduces the damage caused by vibration, and increases resistance to severe shock and thermal variation.

Designed to be compatible with a standard 60-degree bolt, the thread incorporates a 30-degree "wedge ramp" at the base of the female thread. When load is applied during assembly, the Spiralock thread form locks the standard male threads tightly against the wedge ramp, preventing movement in the joint – in short, it holds the bolt tighter than the average thread.

Spiralock says its thread also helps to distribute the joint load throughout all engaged threads, while conventional screw threads place up to 80 per cent of the load on the first two notches of the thread.

Engineer Brian Mann has been with Spiralock for 13 years. Recently his focus has shifted under the title “application engineer” – it is his job to make the transition from standard threads to Spiralock painless for manufacturers.

“It’s not much trouble to switch to Spiralock from a standard bolt. The only difference is the thread,” he told Airframer. “We sell Spiralock in two ways: number one, w....

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 Contact details from our directory:
Lockheed Martin Corporation
UTC Aerospace Systems, Air Management Systems AC/DC Generators, Bleed Air Systems, Mechanical Actuators, Fuel Pumps, Fuel Tanks & Systems, Valves, Automatic Flight Control Systems, Engine Controls, Starters, Pneumatic Systems Equipment, Cooling Systems, Ice Protection/Prevention Equipment, Air Conditioning Equipment, Air Cycle Machines, Gearboxes, Fly-by-Wire Systems, Turbine Engine Starters, Flight Management Systems, Vibration Damping Materials, Fuel Inerting Systems
Stanley Engineered Fastening-Spiralock Self-Locking Nuts, Inserts, Fasteners, Screw Thread Inserts
Beechcraft Corporation Airframer

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