Fastener Locking System
December 2004
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For fail-safe joint integrity in critical applications, STAGE 8 Locking Fasteners, Inc. has developed an innovative fastener locking system that is said to stop joint failure and production downtime by preventing thread loosening from starting, even in counterbored hole applications. GrooveLok™ is a patented fastener locking system, which acts like a small wrench locked onto a bolt head, with the wrench handle braced against a stationary object such as a frame, casting, or protrusion. This is said to stop any counter rotation of the bolt, as well as bolt loosening, until the locking system is removed. The system includes a grooved nut or bolt, an application specific retainer (which serves as the “wrench socket and handle”), and a spring clip, all of which work together. If there is nothing to brace against to stop loosening, a special bridge retainer can fit over two or three bolts, locking them together, or a retainer can be bent over an edge or frame.

The locking system is said to be ideal for applications with counterbored holes, which normally require tedious torque checking and screw re-tightening with typical fastening methods. The company says once the locking system is in place, requiring just a small milled slot adjacent to the counterbore for the retainer to slip into, the fasteners never need to be re-tightened. Thereafter, they can simply be scanned by eye to check for joint integrity, without labor intensive torque gauges or bolt re-tightening. If the clip and retainer are locked in place, the fasteners reportedly retain their full pre-load. Until the clip and retainer are removed, the nut or bolt will not move because they are physically restrained.

In addition, since the fastening system doesn’t rely on fastener threads, clamp load, or anything other than physical restraint to keep nuts and bolts locked in place, the company says no internal or external forces will loosen it until removed. The system retrofits existing components, is fully reusable, and has been used in items as small as eyeglass screws to bolts as large as 8-in holding generator propellers for a hydroelectric dam.

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