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Engineers, however, have successfully attacked these challengeswhile providing new electrical design options with innovative Spiralock self locking threaded fasteners. This re-engineered thread formadds a unique 30-degree wedge ramp at the root of the female threadwhich mates with standard 60-degree male thread fasteners.

The wedge ramp of the self locking threaded fasteners allows thebolt to spin freely relative to female threads until tension iscreated in the male fastener. The crests of the standard malethread form are then drawn tightly against the wedge ramp,eliminating radial clearances and creating a continuous spiral linecontact along the entire length of the thread engagement. Thiscontinuous line contact spreads the clamp force more evenly overall engaged threads, improving resistance to vibrational loosening,axial-torsional loading, joint fatigue, and temperature extremes.

The innovative threaded fasteners with a locking feature integratedinto the thread form compensates for variations in manufacturingtolerances and processing. This locking feature enhances jointreliability even in soft materials and can reduce costly warrantyclaims or potential liability. It also opens new electrical designoptions by eliminating the need for secondary thread lockingdevices or procedures, thus simplifying assembly and inventorymanagement. The fasteners have been used in thousands ofmanufacturing applications to solve design challenges in a widerange of industries.

Eaton Corporation's electrical division chose the Spiralockfasteners and internal thread form for its Cutler-Hammer brandmetal enclosed front (MEF) accessible switchgear. When secured atthe factory, the self locking threaded fasteners and internalthread form are capable of holding the MEF switchgear's bus jointssecure for decades, according to

Paul Parker, a senior engineer with Eaton's electrical division,part of Eaton Corporation, a diversified industrial manufacturerwith sales of $13 billion in 2007.

"The self locking fasteners and internal thread form helped usachieve vibration-resistant locking in our bus design that canwithstand seismic, shipping, operational or thermal-related forcesfor the life of the product," says Parker. "By helping usattain a

no-maintenance bus design, the Spiralock fasteners and internalthread form opened up new design possibilities."

Production changeovers to these self locking fasteners aretypically quick and seamless, often requiring just an exchange oftraditional nuts, wire inserts or simply drilling out andre-tapping existing parts stock.