Nylocs backing out?

Has anyone ever had any experience with or heard of a Nyloc nylon lined nut backing off a bolt?
Here is the situation: I import a very good anchor called a Spade from
Tunisia. They come in two pieces a shank and a fluke which mate together in a tapered socket that locks the shank in position when any load is placed on it. When there is no load the two pieces are held together with a 1/2" stainless bolt and stainless Nyloc nut tightened snug to the sides of the socket. About 1" of bolt extends beyond the nut. The nut is not torqued down because the shank must be loose enough to slip forward into the taper to lock. All the load on the bolt is in shear. There is no force in tension or torque. Overall it is a very solid arangement.
Now the problem. A New Zealand sailor is claiming that his anchor (which thankfully I did not sell) failed because the nut backed completely off the bolt which allowed the bolt to fall out. There is very little vibration and no torque on the bolt. The nut was in good condition, new when installed and had never been removed. Is there any way that a Nyloc nut in good condition could possibly make more than 20 turns on a loose bolt on its own?
--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
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I would think so. But I can't give you the details. My experience has been with screws that are used to hold down and attach sheet metal[steel] roofing. Every once in a while you get a screw or two that will not stay in [yes they are into the substrate]. Over a period of weeks or months they unscrew. You can put them in and they just come back out. I am sure it has to do with the thermal different coefficients of expansion of the various materials. If anyone knows the answer please let us know.
Chuck Pilgrim
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enough

with the conditions you describe, i cannot see this happening with one exception. Either the bolt was undersized, or the nut was oversized, or a combination of the two.
--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
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Anthony wrote:

Or the NZ sailor cut a corner or two when installing, putting the Nyloc in his pocket to save it for another job and swapping in a regular nut. I had a stainless Nyloc nut sieze on me recently. I installed it to only finger-tight, left it for a day, and when I went to disassemble it, it was super-tight. I put a real wrench on it, and broke the bolt clean off. Half-inch bolt at that. That was some tough Nyloc.
Grant Erwin
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Stainless on stainless galls up pretty easy. I use a lot of stainless fasteners on motorcycles (because they get driven in the road salt seasons in NY) and unless I use a good grade of moly anti-sieze on them, it's asking for trouble.
You've never seen fun until somebody bakes a vacuum system and locks all the conflat fasteners into the flanges, because they put it together dry.
Jim
================================================= please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com =================================================
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On Sat, 19 Jun 2004 22:21:56 -0400, Glenn Ashmore wrote:

I've purchase bolts and nuts in bulk and occasionally find one that wasn't threaded or tapped. Perhaps the nut wasn't tapped (or stripped) from the manufacturer and thus installed with only the nylon holding on to the bolt. Now, the part that blows a hole in my hypothesis is that if the nut were not tapped, the hole would be too small to fit over the nut. ...but if it were stripped...
I know you said there is no tension load on the nut, but if the anchor is banging on a rock or something at the bottom, it could (conceivably) hammer the nut off. Or rather, hammer the 1" of extended bolt to the edge of the nut which would then fall off since the threads in the nylon have been beaten/stripped away.
Anyhow, just a possiblity
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Skuke
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||On Sat, 19 Jun 2004 22:21:56 -0400, Glenn Ashmore wrote: || ||> Has anyone ever had any experience with or heard of a Nyloc nylon lined ||> nut backing off a bolt? ||> Now the problem. A New Zealand sailor is claiming that his anchor ||> (which thankfully I did not sell) failed because the nut backed ||> completely off the bolt which allowed the bolt to fall out. There is ||> very little vibration and no torque on the bolt. The nut was in good ||> condition, new when installed and had never been removed. Is there any ||> way that a Nyloc nut in good condition could possibly make more than 20 ||> turns on a loose bolt on its own?
I wonder about a sailor that doesn't check his equipment any better than that. Texas Parts Guy
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Perhaps the Nyloc was defective. Although not often, I have found Nylocs without the nylon insert, which leaves you with a regular nut.
Shawn

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Glenn Ashmore wrote:

I believe the Nyloc's work when the nylon is compressed. If just screwed on, there isn't a locking force down the screw as if against a bulkhead.
What I'd do is double nut - plain nut against the Nyloc. That should do it.
Martin
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Martin Eastburn, Barbara Eastburn
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We had a nyloc nut come off a taper dirve pin on a rotating shaft driving the tap changer on one of our transmission transformers, it caused about $100,000 damage to the transformer. It was an 'engineered' replacement for the original locking mechanism, but it appears to have been defeated by some oil that leaked onto it. Your NZ friend didn't happen to oil part of the anchor did he, perhaps to stop the stainless galling?
regards,
John
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Yep, same here except it was a 100# capacity commerical laundry machine where all 8 nyloc nuts worked loose enough on the front bearing housing to cause one hell of a vibration when the drum spun up to extract speed. Third time in 6 months. Ask the guys from another office who does all the bearing jobs to remove the darn things and go to lock washers and nuts. Made an inquiry a few days later at main office and found they went back with nylocks again but used thread lock this time. I don't know but suspect I'll be back on that job in a few months for the same vibration problems. I tend to go with the idea of oil on the threads or even cheap nyloc material in nuts, perhaps just not correct torque applied to nuts.
Rusty Bates

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On Sun, 20 Jun 2004 15:49:22 +1000, "john johnson"

I've seen the nylon wear to the point of no longer holding from repeatedly threading it onto/off of the bolt.
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If I had to guess, I would also say wear was the problem. I don't believe the government allows nyloc fasteners to be reused, or they limit how many times they can be used. If I remember correctly, the mil specs call out a running torque for the 10 installation because it decreases with each cycle.
Vince
snipped-for-privacy@thanks.com wrote:

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Yes. That's why critical fasteners should be safety wired.
Gary
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And here's a link to all you ever wanted to know about safety wiring.
http://www.whizwheels.com/Tips/safetywiring.html
In particular note this paragraph near the bottom of the web page, and I quote;
"Putting Holes in Your Nuts"
"This need not be as painful as it sounds. You just need a drill with a very sharp bit, a vise to hold your nuts, a center punch, and a steady hand."
(No really, thats what the man says. See for yourself.) (-8
Dennis van Dam
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wrote:

One of the finest bits of technical writing I've seen in a while.
Shawn
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Shawn,
If I could table my disposition to appreciation of sophmoric humour for just a moment, I would comment I absolutely agree with your assesment.
This article is a comprehensive disemination of valuable technical imformation, the likes of which, it's frequently required to wade through no end of crap and commercialism, to find online.
But obviously, (in my opinion), the man intended to slide in that bit of humor for us to find and appreciate.
So if you're commenting on the quality and value of the over all article, I agree with you completely and if you were more specifically commenting on the humorous content of that one paragraph (along the lines of my own particular appreciation of that paragraph), I agree with you completely! (-8
Dennis van Dam
PS To speak to Glenn Ashmore's specific inquiry, I have fairly extensive experience (although none as a function of formal training) with nyloc nuts and I've never experienced or heard of a fresh (installed one time only) nyloc backing off under any circumstance. I would qualify this statement as being in the context of extensive knowledge of hang gliding technology (no vibration environment) and to a lesser extent ultralight technology (VERY HIGH vibration environment....and one in which saftey wiring techniques are employed extensively, which are not employed in hang gliding technology (although it's not out of the question to find critical hang glider nylocs backed up by split rings or safety pins (tantamount to safety wiring)).
Speaking from a standpoint of total ignorance and in acknowledgement of a prior posters supposition, I would examine the possibilty that, for extensive periods, immersing the nyloc in water, and then additionally, that it's salt water may have some bearing on the condition.
(But I couldn't find anything online to support this supposition)
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Just a note about Nylock nuts. Yeaserday I had to dis-assemble a pulley that had been in service in a salt water tidal installation for about fifteen years - stainless steel bolt and stainless steel nyloc nut. There was absolutely no evidence that the nut had degraded in any way (It was holding well and the torque needed to back it off was what could be expected of a brand new one.) despite being in and out of the tide twice a day for at least fifteen years. Just a real world observation. Regards. Ken.
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Perhaps a stover type locknut should be considered.
Shawn

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One of my products uses 2 ea. 1/4-20 Nylocs and we ship 300 a day. I have yet to see a nut failure in the 4 years of making these. However, we have seen about .5% of the nuts defective out of the box. The guys in that work center have good eyes and seem to catch them during assembly. ( I put their names on the box labels) The usual defects are: no insert, cocked insert, undersized insert, broken or cracked insert, malformed insert pocket. So, take your pick. I don't think that Nylocs are meant to be security nuts, and I wouldn't trust them in that type of situation. Castle nut and pin please!
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"Glenn Ashmore" < snipped-for-privacy@cox.net> wrote in message
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