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Distributor's Link Magazine Spring Issue 2017 / Vol 40 No3

26 THE DISTRIBUTOR’S

26 THE DISTRIBUTOR’S LINK Guy Avellon Guy Avellon has been in MRO and Fastener Distribution for over 30 years, in such positions Sales Engineer, Chief Engineer, Manager of Product Marketing, Product Engineering & Quality and Director of Quality & Engineering. He founded GT Technical Consultants where he performs failure analysis, lectures on fastener safety, works for law firms and designs/audits Quality systems. He is a member of SAE, is Vice Chairman of the ASTM F16 Fastener Committee, Chairman of the F16.01 Test Methods Committee and received the ASTM Award of Merit in 2005. Guy can be contacted at 847- 477-5057, Email: ExpertBoltGuy@gmail.com or visit www.BoltFailure.com. WHAT FASTENER DISTRIBUTORS NEED TO KNOW ABOUT KEEPING FASTENERS TIGHT - PART 2 In the previous article, Part 1, I stated that there was no single product that will serve the needs for vibrational resistance for all applications without having some limitations. This is why we have such a variety of products on the market. However, there is one universal product that has been around since the flood waters have receded: the lock washer. Billions of lock washers are manufactured and sold every year. Why do we use so many of these when there is a variety of other locking devices available on the market that offer far superior performance to the venerable lock washer? Convenience, habit, easy to use or inexpensive? As far back as 1969, the SAE (Society of Automotive Engineers) recommended against the use of helical spring lock washers with any Grade 8 (10.9) fastener and in any critical application. In the early 1980s, the specifications were removed from the SAE Handbook. Since then, there has been no automotive fastener assembled with a lock washer, especially on a Grade 8 or 10.9 fastener used in a critical application. However, specifications and testing methods can still be found in the IFI (Industrial Fasteners Institute) Handbook referencing the ANSI/ASME B18.21.1. Originally, lock washers were manufactured from a medium-high carbon steel and heat treated to a range of 45-56 Rc. They were furnished either as treated or electroplated with zinc. However, this presented problems with hydrogen embrittlement (Figure 1). Hydrogen embrittlement is a delayed but sudden brittle fracture caused by the absorption of atomic hydrogen into the steel from the cleaning and plating processes. Over the past several decades, lock washers have been made from a medium carbon steel heat treated up to a hardness of 45 Rc. The common practice now is to have CONTRIBUTOR ARTICLE FIGURE 1 the lock washers mechanically plated with zinc metal flakes to minimize the potential for hydrogen embrittlement. Since the hardnesses of the lock washers were lowered, a new problem developed with some overseas manufacturers: they were too soft. The opened part simply spread open even further when assembled (Figure 2). FIGURE 2 The common lock washer is a helical spring. At one point in time it was referred to as a ‘split washer’ since the ends are open. One end is bent slightly upwards, the other end is bent slightly downwards. Both of these ends have sharp end corners from the forming operation, which may help to secure the lock washer by digging into its respective surface. CONTINUED ON PAGE 104

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