Elastic lock nuts + cotter pin

[MintJulep]

I have a client who wants to use elastic lock nuts (nyloc) plus a cotter pin "just in case, to prevent the nut from falling off".

Imagine a bolt with a cross drilled hole through the threads - as you would use with a castle nut and cotter pin.

When you thread an elastic lock nut over this hole, the edge acts as a cutting tool, and actually cuts into the nylon ring of the nut - often leaving a nylon chip inside the hole. It seems obvious that this would reduce the effectiveness of the elastic lock nut.

Can anyone point me to an "authoritative" publication that covers this?

 

[CoryPad]

A publication that covers the use of a nylon-insert nut plus a cotter pin? There is none.

You probably could find something by trolling throughout MacLean-Fogg's ESNA division to find someone who may have some test report.

MacLean ESNA®
611 Country Club Road
Pocahontas, AR 72455
(870) 892-5201

http://www.mfmvs.com

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[KENAT]

Sometimes governments or airforces etc generate these types of reports. I doubt you'd find one specific to your application but a more general one about using damaged nylocs may exist. A quick google search didn't find me one though.

Could ask in military or aerospace.

Could you check the torque of a damaged nyloc or equivalent?

Are the bolts specials or off the shelf? A generous de-burr or csk on each side may reduce the problem.

Alternatively could you use patched bolts/screws/studs and regular nuts?

KENAT, probably the least qualified checker you'll ever meet...

 

[MintJulep]

To clarify:

I'm looking for a document that states that using an elastic stop nut on a bolt with a cross-drilled hole will damage the nut.

I'm not looking for something that says this configuration is ok.

 

[HgTX]

How about a closeup photo of your damaged nut with the little nylon chip?

Hg

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[SnTMan]

I'd tack weld it as well

Mike

 

[KENAT]

"I'm not looking for something that says this configuration is ok." But what if it is?

What if the nyloc works OK despite being a little messed up?

My former employer did similar on aerospace equipment but I think it was an all metal stiffnut, not a nyloc. I can't recal for sure.

Sorry not really an answer so I'll stop before I really annoy you.

KENAT, probably the least qualified checker you'll ever meet...

 

[MintJulep]

Kenat,

I'm only interested in information that supports what I believe, contrary documentation is not welcomed .

Seriously, if you can point me to something convincing that says it's fine and dandy I'm open to changing my opinion.

I can see it be "ok" with an all-metal lock nut. No nylon to cut.

HgTx,

You'd have to meet my client...

 

[HgTX]

I was afraid it was something like that.

Hg


Eng-Tips policies: faq731-376

 

[CoryPad]

I knew what you meant. My answer is that I don't think there is a document that discusses this issue (pro or con).

 

[MikeHalloran]

Absent the castellations, whatever turns the nut has the mechanical advantage of the thread working with it, so the cotter pin might be less effective than you'd wish.

However, I could swear that I've seen (large) elastic stop nuts with castellations.

I could also swear that I've seen patched bolts that are also cross-drilled, so you could use them with ordinary castellated nuts and cotter pins. A patch on the bolt never has to cross a hole.





Mike Halloran
Pembroke Pines, FL, USA