high re-use locking anchor nuts/nutplates 2

[Jpbingley]

Hello,

I'm looking for high re-use locking anchor nuts, imperial, for an aerospace application. I can't find much nor evidence of high re-use where the locking method is good for many cycles.
Can anyone help?

Cheers.

 

[MintJulep]

How many cycles?

 

[Jpbingley]

That's one of issues, the number of cycles is a bit of an unknown. I would estimate anywhere from 20 to maybe 50.

 

[IRstuff]

It depends. Serrated locking washers reuse is in the range of 5 to 20 times:

https://heico-lock.us/technical-inf...washers can be,surfaces must face each other.

http://www.as-well-eng.com/datasheet/Nord-Lock/NORD-LOCK Catalog.pdf

Nevertheless, each reuse will entail some additional distortion of the surfaces involved.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[drawoh]

Jpbingley,

How are you going to track how many times you have re-used a nut? What will this process cost, and how much money are you going to save?

If you want to keep things simple and safe, your nuts either are not re-usable, or they are infinitely re-usable. Consider asking your safety approval people what kind of latches they like.

--
JHG

 

[MintJulep]

Great point by drawoh.

Does it really need to be a threaded fastener?

 

[JStephen]

"Anchor nut" sounds big and heavy. "Aerospace application" sounds small and light. But anyway, what comes to mind are "castellated nuts" (had to look the name up), which are definitely the big/heavy option.

 

[LittleInch]

Aerospace and you want to nickle and dime this??

At 20 to 50 times I think you need something different to a nut.

Or a new one every time.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

You might look at some of the prevailing torque lock thread designs. They are more durable than most but I don't know what the limit is.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[3DDave]

I looked for split and beam nuts. They look as if they would operate for a few dozen cycles, but are mostly proprietary and differ enough it's not easy to tell which would work for this application.

The best defense is a correctly designed threaded joint with sufficient elastic deformation that preload won't be lost in use. The main worry in any locking system is, if the fastener preload is insufficient that the locking element will retain the fastener and not leave an obvious clue that the fastener is no longer doing the job, leading, in some cases, to rapid fracture from fatigue.

 

[drawoh]

JStephen,

How many times can I re-use that cotter pin?

--
JHG

 

[MJCronin]

Cotter pin re-use ?

OMG ....

Or was that sarcasm ...???

MJCronin
Sr. Process Engineer

 

[MintJulep]

My imagination of "anchor nut" falls within this spectrum.

If Jpbingley ever comes back maybe they could fill in some blanks.

 

[tbuelna]

Jpbingley,

If you follow proper aerospace procedure for installing threaded fasteners, the actual number of installation/removal cycles of a self-locking nutplate (or "anchor nut") is irrelevant. The prevailing torque of an interference type thread locking feature, like the ones used on self-locking nutplates, should be measured at every installation to verify it is within limits that you specify. If the measured prevailing torque is outside your specified limits, the self-locking nutplate (or anchor nut) should be replaced, regardless of how many installation/removal cycles it has.

However, if you simply want to get an idea of how many installation/removal cycles a particular type of self-locking nutplate might be good for, take a look at standard self-locking nutplate designs like MS21060 . You can find the qualification test requirements for this nutplate in MIL-DTL-25027 including installation/removal cycles and prevailing torque limits.

One thing in general to consider with interference type self-locking devices, is that small thread sizes tend to have lower lifecycle capability.