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Nylocs backing out?

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)

Reply to
Dennis van Dam
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When I worked for a plastics company we tried on numerous occasions to document the absorbtion of water. In spite of claims by plastics manufacturers we were never able to identify any appreciable absorbtion of water. We tried long term soaking, boiling, micro waving etc. and could never determine any increase to size or weight. When questioning the manufacturers, we could never get a definitive answer

- only that it does absorb water and it seemed that they really didn't know how much water it could actually absorb. I doubt you coud get enough water in to make a difference.

Reply to
Tom

That's interesting Tom, I used to make parts from nylon for boats. Bearings for prop shafts being one. And we would rough machine them, soak in water for at least a few days, and then finish machine. They swelled in the water. We measured a few thoudandts. ERS

Reply to
Eric R Snow

Nylon is horribly hygroscopic. Nylon fiber is an excellent choice if you want to make a humidistat or hygrometer. In some cases they actually spray water into the packaging of nylon parts after molding (the plastic is dried before molding) so the parts will be more or less normal when they come out of the plastic bag. Last time I looked this up, IIRC, I saw rather wide (more than 2:1) differences between different nylons in the dimensional changes with moisture..

Best regards, Spehro Pefhany

Reply to
Spehro Pefhany

Chances are you never got the parts hot enough to desorb the water that was in them. To properly do this you need to bring bulk parts above the boiling point for extended periods. We used to anneal nylon 6,6 for about two days, in gas fired furnaces.

There was a large amount of water vapor evolved and the parts machined much differently after this was done.

Jim

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Reply to
jim rozen

I can remember soaking our nylon radiator fans in water before we ran the durability cycle on them...

Reply to
Rick

||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

Reply to
Rex B

Hmm. Red locktite, safety wire, and a castelated jam nut with cotter pin!!

Cotter pin to be coated after assembly with bubble gum....

Jim

================================================== please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ==================================================

Reply to
jim rozen

I've had locking insert nuts arrive with no inserts(no threads, too). Usually on no-name import hardware, though. I've also had them back off due to vibration, usually after repeated assembly-disassembly cycles. I've also had the insert get torn up running down a raggedly-threaded bolt and fail to lock. If there was no vibration, how did the NZ sailor's nut come off? They don't just move themselves. If the nut is to be positioned so it's not tight, it needs a check nut and/or thread-locking compound. Bolts aren't supposed to be used in shear, it sounds like an application for a pin with retaining clips or wiring.

Stan

Reply to
Stan Schaefer

My suspicion is that the nut was never tightened in the first place. The anchors are shipped from Tunisia with the nut just threaded on so that the anchor can be disassembled for final shipment without messing up the nylon. Regardless, from the answers I got here I am going to start drilling the bolts for a stainless cotter pin.

BTW Nyl>

Reply to
Glenn Ashmore
[ ... ]

So -- *how* was the machining different? Was it better machining or poorer machining when dry? Better chip control perhaps?

Thanks, Don.

Reply to
DoN. Nichols

Pink Loctite by Fleer? :-)

Enjoy, DoN.

Reply to
DoN. Nichols

I was *gonna* say something about baby shit on a wool blanket but thought that would needlessly lower the tone.

Jim

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Reply to
jim rozen

The stuff is nearly unmachineable in the unbaked state. Once it's been annealed one can rough at a rapid rate, high SFPM and the chips just fly off the tool balistically. We would routinely rough a fifteen inch diameter part at the max that the Okumas could do which was around 3K rpm IIRC. The roughing feed was inches per second and at those rates the material did not come off as a continous string but would fragment into powder. The chip pans would be full of fine nylon particles along with the linear strings from the finish cycle.

Often the trick to getting the swarf free of the part when doing finish cuts would be to bump up the speeds and feeds till it would clear into the chip pan on its own.

Worst was single-blocking parts at low speeds to proof out a new program.

Jim

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Reply to
jim rozen

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.

V>>

Reply to
Vince Iorio

heat will kill a nyloc. also there is some property of stainless on stainless at depth that causes super fast corrosion (i'll ask my dad he used to build deep sea probes and ran into it in the 70's)

laz

Reply to
Laszlo

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.

Reply to
Ken Davey

Yes.... Nylocks are not recommended when the fastener may be subject to rotation. I'm not terribly sure, from your description that this is possible, but if wave action can possibly cause you problems, it will.

A more acceptable and reliable solution would be a cotter key or safety wire. Monel seems to be the material of choice...

Note that the accepted manner of using an anchor shackle is to safety wire the pin.... and they are drilled for just such attachment...

Reply to
Gene Kearns

If you use a nylock nut inside of an hydraulic cylinder to keep the piston on the piston rod, the nut will come off. A stover nut will hold. Cross drilling a regular nut for a cotter pin will also work, but if there are any burrs the thread on the rod can be damaged in case of disassembly. HTH

Reply to
John

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