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Elastic lock nuts + cotter pin

Elastic lock nuts + cotter pin

Elastic lock nuts + cotter pin

(OP)
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?

RE: Elastic lock nuts + cotter pin

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: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.

RE: Elastic lock nuts + cotter pin

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...

RE: Elastic lock nuts + cotter pin

(OP)
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.

RE: Elastic lock nuts + cotter pin

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

Hg

Eng-Tips policies:  FAQ731-376: Eng-Tips.com Forum Policies

RE: Elastic lock nuts + cotter pin

I'd tack weld it as well:)

Mike

RE: Elastic lock nuts + cotter pin

"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...

RE: Elastic lock nuts + cotter pin

(OP)
Kenat,

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

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...

RE: Elastic lock nuts + cotter pin

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

RE: Elastic lock nuts + cotter pin

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

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