FALL 2015

30 THE DISTRIBUTOR’S

30 THE DISTRIBUTOR’S LINK Carmen Vertullo Lead Trainer, Fastener Training Institute ® FASTENER TRAINING INSTITUTE ® 5318 East 2nd Street #325, Long Beach, CA 90803 TEL 562-473-5373 FAX 661-449-3232 EMAIL info@fastenertraining.org WEB www.fastenertraining.org WASHERS - WHAT ARE THEY GOOD FOR? Our Third and Final In A Series Of Articles On Washers In the previous two articles in this series we looked at the most common flat washer and lock washers, mostly from ASME B18.21.1. This article will focus on special washers. Those that provide some feature or function beyond the common flats and locks. Some of these features and functions are: extraordinary vibration resistance exceptional load bearing capability load indicating features torque resistance features sealing capability torque-tension control finish and appearance features dimensional control retention of components electrical insulation surface protection accommodation of sloped surfaces • part of an assembly including an integrated screw or nut The variety of special washers is endless and there is no way to cover every type in a short magazine article. We will present a few of those that are among the best solutions to fastening problems and the most likely to be asked for in the fastener distribution supply chain. Some of these are specification washers, some are generic but not to any particular specification, and some are brand names. Please consider that the mention of a particular brand or type of washer, or the absence of mention, does not imply recommendation or disfavor - even if I say it’s one of my favorites. Many of these special washers are very application specific. Some are engineered fasteners or parts of engineered fastening systems. You should be sure your customer’s engineering staff has the technical knowledge to specify and use them appropriately. Starting with one of my favorite fastening solutions, the TECHNICAL ARTICLE wedge lock washer. This is a two part washer with identical upper and lower halves. It provides the bolted joint with extraordinary resistance to vibration loosening. You know them by their brand names such as Nord-Lock ® and HEICO-LOCK ® . The most important thing to know about these washers is that they work as advertised. They are available in all sizes, inch and metric, and in a variety of materials and coatings. There are few things to be aware of when using them, but the suppliers have an abundance of technical information on their websites and they offer engineering help for your applications. WEDGE LOCK WASHER They work using friction and a mechanical lock. The side of the washers facing the assembled components and the nut or the bolt bearing surface have serrations. These serrations grip the bearing surfaces and prevent rotation. The side of the washers facing each other have interlocking ramps, or wedges. Once tightened, the bolt or nut cannot be rotated without the ramps working against each other to actually increase the bolt load. They look simple, but there is a lot of not-so-obvious engineering in the design of these ramps. These washers will require higher installation torque than standard flat washers, and will increase the break-loose torque during disassembly. CONTINUED ON PAGE 150