The USA standard on this used to be MIL-B-5087, but I'm sure that must have been superseded by now. Still, it essentially said no star washer, use split-ring washers only. The rationale was stars only made tiny point-contacts, which could be vaporized and cause arcing under high-fault conditions. It didn't talk about Belleville washers, which have a smaller but stiffer compression range than a split-ring, but I think there is nothing inherently bad about a Belleville.
Either way, you never want the washer or bolt or nut to try to punch through crud to make the bond. Rather, you prepare the base metal surfaces carefully, abrading a zone down to base metal, possibly plating the exposed metal, and torqueing to specs. Ed Price WB6WSN Chula Vista, CA USA -----Original Message----- From: Douglas Nix [mailto:[email protected]] Sent: Thursday, July 18, 2013 6:31 PM To: [email protected] Subject: [PSES] Lock washers for bolted bonding connections Colleagues, Recently I had a conversation with a German colleague who told me that 'star washers', commonly used for making vibration resistant bonding connections in North America, are not permitted for this use in Germany. Only lock washers meeting DIN 6796, commonly called 'Belleville' washers, are accepted. When I pressed him for a standard or a regulation that made that requirement, he was not able to provide one. I know from experience that Bellville washers are superior in performance, and the serrated version will definitely cut through any surface coating to the bare metal substrate. Star washers can usually do this, but they do not provide as uniform a tension on the bolt as a Belleville. Any comments on the regulatory or standards-based source for this requirement? Sent from my iPhone Doug Nix [email protected] Mobile: (519) 729-5704 Office:(519) 650-4753 Fax: (519) 653-1318 - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
