I believe you are talking about Pem inserts or Nutserts. They take expensive special tools to insert correctly, but they do work great when done right. Regular aircraft Rivnuts are a lot more tollerant.
Brian Kraut Engineering Alternatives, Inc. www.engalt.com -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On Behalf Of Mark Langford Sent: Friday, April 22, 2005 10:27 AM To: KRnet Subject: Re: KR> rivnut question OZ wrote: > The "real" rivnut tool isn't cheap and neither is the "simplified" model, > but there is a mandrel available such that you can install them using your > regular pop rivet puller. My question is, does a regular pop rivet puller > have enough backbone to pull a rivnut? Sound like Serge's tool will work fine, given his experience, but you do need to be careful. The project I just finished up (at work) required several hundred knurled rivnuts (which are less likely to spin), so we learned a lot about them in the fabrication process. Maybe Serge and I are talking two completely different kinds, so I can only speak to the ones we used, which came from McMaster Carr. We cheaped out and bought the "simplified model" ($170 or so), but I don't see a lot of difference between that and the $250 model. The problem with that is if you don't get it tight enough, the rivnut just spins, and you can't tighten up the bolt. If you squeeze it too tight, the threads get scrunched up and distort, and the bolt binds and the rivnut spins. You'd think after several hundred, you could get the feel of it, or get it adjusted correctly, but it never happened. Keep in mind that these guys are not just "Bubbas", they're well-trained experts who commonly fabricate space, defense, and nuclear hardware day-to-day. We eventually drilled every one of them out and welded custom made aluminum inserts into those holes, and have had no problems since. These were relatively large rivnuts (3/16", 1/4" and 3/8"), so it may be that the smaller stuff that we'd use on airplanes isn't as touchy, but I personally have deleted them from my fastening options list, next time I have something in a blind hole that needs threads. Some of these rivnuts were $4-5 each, but the bosses we welded in were made overnight for about thirty cents each on our CNC lathe, and were welded in place about as fast as you could use the rivnut installation tool, but that's not an option for most homebuilders... Mark Langford, Huntsville, Alabama see KR2S project N56ML at http://home.hiwaay.net/~langford email to N56ML "at" hiwaay.net _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
