Distributor's Link Magazine Summer Issue 2015 / Vol 38 No3
34 THE DISTRIBUTOR’S
34 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? Second In A Series Of Articles On Washers In the first article on this series we looked at about ten of the most important functions of washers of all kinds and we focused on the most common inch size flat washers –those called USS flat washers, SAE flat washers in accordance with ASME B18.21.1, and ASTM F436 hardened flat washers. This article will focus the most common types of lock washers: split-lock washers and tooth-lock washers from ASME B18.21.1. Split Lock washers are called Helical Spring-Lock Washers in the standard. We will explore the important aspects of their dimensional requirements, material requirements, testing procedures, coatings, variations in style, and usage considerations. If you have been informed on these basic styles of lock washers you have probably heard negative opinions such as “they don’t work” or “they are a waste of money”. This is not true. Most of the negative opinions are based on the results of vibration testing of fasteners with these lock washers compared to no lock washers, and compared to other types of lock washer or lock nuts. Split lock washers and toothed lock washers actually serve important and valuable functions when applied appropriately. The key to understanding how to use these lock washers effectively is to understand their function and their limitations. By definition in the specification, tooth lock washers serve to “increase the friction between the screw and the assembly”, while split lock washer are intended to “compensate for developed looseness between component parts of an assembly, and provide a hardened bearing surface”. TECHNICAL ARTICLE Split-Lock Washers Split-lock washers come in four different series, regular, heavy, extra duty, and high-collar. By specification they range in size from No. 2 through 3 inches, but larger sizes are available. Eight different materials are designated, however other materials may be specified if requested. When designating split-lock washers you should include the type, specification and year of issue, size, series, material and coating. For Example: (1) Helical Spring-Lock Washer, ASME B18.21.1, 2009, 3/8 in., Extra Duty, Carbon Steel, Mechanical Zinc per ASTM B695, Class 55. (2) Helical Spring-Lock Washer, ASME B18.21.1, 2009, 1/2 in., High-Collar, 304 Stainless Steel, passivated per ASTM A380 Split-lock washers are characterized by their helical shape - one coil of a spring, and their trapezoidal cross sectional area. CONTINUED ON PAGE 146
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