27 April 2018
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An illuminating presence

Helicoil Screwlock threaded inserts have been specified as part of a major eco-friendly European lighting project.

When the regional Government covering the Bielefeld area in Germany recently instigated a programme to replace ‘old style’ (and expensive to run) street illumination with state-of-the-art energy-saving lighting, it commissioned lighting experts WE-EF to fulfil the contract.

Starting with a blank canvas, the WE-EF design team considered all the viable material options for the structures, which were to carry and house new LED street light units, and subsequently settled on using environmentally-friendly unmixed recycled aluminium alloys.

With the application involving a large number of units having to be installed in busy public places, the manufacturer needed absolute assurances about the ‘full service life’ structural integrity of the equipment, prior to finalising the design. To this end, it undertook a series of tests and one of the things discovered as a result was that the threaded fasteners used to affix the light units to the head of the lamp posts could work loose.

In partnership with the WE-EF design team, Böllhoff engineers suggested trialling the Screwlock version of the standard Helicoil threaded insert, as the company considered it would provide a simple, yet effective and cost-efficient, locking solution to the apparent ‘loosening’ problem. The results proved enlightening for all, with extensive retesting demonstrating that, with the Helicoil Screwlock inserts now installed, all of the essential design and service life requirements had been exceeded.

Another advantage became apparent through the selection of Helicoil for this application: in addition to providing the necessary threaded fastener security, the product also delivered a guarantee of resistance to corrosion over a service life of decades in this outdoor environment.

The screwlocking facility that helped to solve the challenge faced by WE-EF is also available on Böllhoff’s recently introduced Helicoil Plus range of threaded inserts. Unlike the ‘standard’ Helicoil, the new ‘Plus’ version features a reduced diameter first coil that ‘leads’ the remainder of the insert into the hole. As it seats into the hole, the insert thus finds itself under significant and equalised radial compression inside the material, providing enhanced pull-out strength – and, in the case of the screwlocking version, with an elastically-resilient frictional locking coil exerting resilient pressure on the flanks of the screw.

For applications where no locking facility is required, Helicoil Plus inserts are also available in free-running specification and come with precision-formed rhombic profiles on both sides to provide an internal thread that is true to size along its entire length.

Commenting on the WE-EF lighting success, Böllhoff’s Clive Brown observes: “By working alongside our customer’s design team, we gained valuable insight into their needs and, between us, engineered a solution that delivered all the in-service demands that had been established for both threaded fastener security and corrosion resistance.”

Brian Wall

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Bollhoff Ltd


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