28 August 2013
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Clinching the market

Steve Wallis explains to FAST why the self-clinch is such a superstar among fasteners and what its future may hold

From domestic appliances and medical equipment to automotive, marine and telecommunications applications, the self-clinch is one of the most versatile, effective and widely used fasteners in the business. A global front-runner in the design, manufacture and supply of these essential components is TR Fastenings, a world player in the fastener and fixings industry which works closely with manufacturers and distributors to ensure its self-clinch range stays at the cutting edge of fastener technology.

The invention of the first self-clinch fastener in the United States back in the 1940s marked a major milestone in the history of sheet metal joining. Significant developments in manufacturing design and technology during World War Two had led to the increased use of sheet metal that was too thin to be tapped by conventional methods.

The self-clinch fastener solved the problem by providing load-carrying threads that would withstand hard tugs and torque loads. These neat little fasteners could be installed permanently in thin ductile metal sheets by pressing them into a properly sized hole and squeezing them, either during fabrication or final assembly. This process forces displaced sheet material to cold flow into an annular recess in the shank or pilot of the fastener, locking it in place. A serrated clinching ring, knurl, ribs, or hex head prevents the fastener from rotating in the metal when technicians apply tightening torque to the mating hardware, job done.

The advantages of self-clinch fasteners were immediately seized upon by design engineers and, seventy years on, with huge advances in manufacturing processes and self-clinch fastener technology continuing apace, the self-clinch market is at an all-time high. British firm TR Fastenings, the trading arm of Trifast PLC, first introduced its own brand of TR Hank self-clinch fasteners in the early 1990s. Originally offering just clinch nuts, stand-offs and studs, the TR Hank self-clinch range now comprises over 750 individual items , including numerous variations on studs, stand offs, nuts and panel fasteners, which are used in a number of industry sectors, including medical equipment, marine, automotive, white goods, telecommunications, electronics and general engineering. The range generates an annual turnover of approximately £10 million and is the company's biggest seller of its branded product range.

Product Innovation
Even in the company's 40th anniversary year, TR is not content to rest on its laurels. The company invests heavily in product development and market research and the range continues to expand. The latest products from the TR stable include concealed head studs and standoffs, ideal for applications where a totally smooth and hidden finish is required, and aluminium nuts and studs, for applications such as the telecommunications industry where light-weighting is becoming ever more important.

Where stainless steel sheets need to be joined, then TR's range of hardened stainless steel, nuts, studs and standoffs fits the bill, while its new low displacement studs can be inserted as close as 2.8mm to the edge of sheet metal, making them ideal for small technical applications, where space may be tight.

Over the past few decades the number of manufacturers and distributors globally has increased greatly, but caveat emptor: quality cannot be guaranteed from everyone and is of paramount importance as these fasteners are often used in industries where a certain amount of corrosion resistance is required. All TR Fastenings' products conform to industry standards and are RoHS compliant.

The variety of styles available also offers a number of installation methods with varying performance levels, allowing users to easily find the product to suit their individual application. With its network of UK and global manufacturing and distribution facilities, the company has a proven track record of supplying quality products at competitive prices, all with the quality assurance customers' demand. Once a partnership has been established, TR can provide assistance and advice throughout the manufacturing process.

Taking the Test
A self-clinch fastener's reliability depends on many factors, beginning with a properly sized hole, the thickness and hardness of the host panel, proper installation, and the application. TR Fastenings has comprehensive testing facilities in each of its manufacturing locations, where its trained technicians perform testing and provide complete analysis on tensile strength, compression, in-sheet performance, hardness, thermal cycling, image analysis, corrosion and plating issues.

Traditionally, three tests determine reliability:
• Torque-out test: Determines a fastener's ability to resist rotation within the panel. This test is often made on the fastener's head with values usually exceeding the ultimate torsional strength of the mating screw or nut.
• Pushout test: Indicates a fastener's axial resistance to being pulled out of the sheet. It should be roughly 5 to 10% of the force used to install the fastener.
• Pull-through test: Pinpoints a fastener's resistance to being pulled through the metal sheet when applying a clamping torque.

Among the processes performed by sheet-metal fabricators, the efficient installation of fasteners can traditionally be one of the most challenging. The work typically can be labour-intensive, often requiring time-consuming tooling changeovers to install different types of fasteners. The growth in applications for self-clinching fasteners over the years has helped to mitigate concerns by reducing the amount of required hardware (such as loose washers, lock washers and nuts) and requiring only a single mating piece to complete final component attachment.

Roger Griffiths, commercial manager of CTL Metalwork, one of the UK's foremost suppliers of precision sheet metalwork, is a regular customer of TR Fastenings and uses self-clinch fasteners to produce front panels, chassis and covers for the pro audio industry. Griffiths commented: "Using self-clinch fasteners saves us both time and money – they are simple and quick to install which lowers production costs, and benefits both us and our customers."

Going Greener
By developing and adopting more energy-efficient technologies, manufacturing industries can boost their productivity and competitiveness while improving energy sustainability and reducing environmental damage. Advances in automated fastener-installation press technology have contributed significantly toward resolving traditional equipment-related issues and promoting both green and cost-effective operations.

TR Fastenings recommend Haeger, the world leader in the development of innovative fastener insertion technology solutions. Haeger machines allow the insertion of up to four different fasteners in a single handling of a part. The technology offers the single most significant boost to hardware insertion productivity since the introduction of automatic tooling systems.

Haeger has recently introduced two new machines to its range, including the Haeger 516 Plus Fastener Insertion System - an extremely accurate fastener insertion system that enables the operator to apply full tonnage at any point in the stroke. This allows the use of any tooling length and thus the ability to fit nearly any shaped work piece in the machine. The Haeger 516 is also set to be a popular machine thanks to its low energy usage, patented operator safety system, fully hydraulic system, and integrated tooling storage points.

Also recently introduced is the new Haeger 824 WindowTouch 4e and OneTouch 4e fastener insertion systems. The Haeger 824 models offer more reliable fastener feeding and more workpiece accessibility than ever available before.
"Environmental benefits go hand-in-hand with the economic benefits of these two new models," explained Andrew Meachen, service manager at Shear-form, the UK distributor of Haeger.

Looking to the future, TR Fastenings is committed to further developments in its self-clinch range, in response to customer demand and in particular the giant manufacturing capabilities in Russia and the Far East. Combined with its environmental and economic benefits as well as its versatility, the self-clinch fastener is set to stay a firm favourite.

Steve Wallis is product sales development manager at TR Fastenings. He has been involved in the fastenings business for 27 years, 20 of those at TR Fastenings and is currently responsible for the sales of some of TR's branded product range including self-clinch, Hank rivet bushes and K Nuts. His responsibilities include the introduction of new product ranges and sales development.

Paul Gay

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TR Fastenings Ltd

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