Ideas on how to make a nylon Stiffnut 'less stiff'

Can anyone suggest a method of making a commercial Stiffnut 'less stiff' in order to reduce the torque required to tighten things up. I am using a 16mm nylon insert nut with a commercial zinc plated bolt in a rather confined space requiring the use of a special purpose 2-Pin spanners and given the fact that the spanner pin diameter is limited to 3/32" diameter it is proving essential to reduce the degree of stiffness imposed by the nylon insert. In the absence of a 16mm tap I have tried running the nut up and down the bolt which has eased things a little but it is still too stiff for comfort. Before resorting to abrasives and the like I just wonder if anyone may have some useful suggestions worth trying.

Run a tap through it.

O.K. You don’t have a tap ... Make a very basic one by modifying a bolt.

MichaelG.

Edited By Michael Gilligan on 05/06/2021 21:12:55

It may help to warm the nut and some lube may help, nyloc nuts usually do relax a bit with use but it sounds like yours is not giving up easily.

Mike

Take the nylon insert out, if you ran a tap through it, it would reduce the friction to make it ineffective anyway, I assume it coming loose isn't an issue as you want the nylon insert to have no friction?

Yes, I had considered warming it up a little. Will try this in the morning. Thread cutting lubricant appeared to have little effect.

Use an ordinary nut, it's use for what was intended is pretty much destroyed anyway.

Robert Butler

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Surely Greensands is looking to make the nut “less stiff” not free-running

A few turns of a taper tap would do that nicely.

MichaelG.

By the time it's loose enough to turn easily with your fingers, surely all the benefits of the nylon insert have gone? Car manuals generally advise to replace these when taken off, I would assume their testing shows the nylon needs to be pretty tight to work properly.

Just to be clear, I'm not saying removing it is a good idea, just pointing out they're only really effective when tight, he gave the impression he wanted convenience rather than proper assembly.

How about using a plain nut with a low strength and slow acting/setting thread retainer such as Loctite; other thread locking fluids are available. This way you get the best of both worlds with a nut that can be tightened with minimum force and after 24hrs or so a nut that will be more secure than a bodged nyloc nut, probably better than a non bodged nut.

If this is a fit once installation and you don't plan to remove the nut then use a medium or high strength thread retainer. Horses for courses as they say .

Hope this helps.

Martin W

I don’t think I have access to the standard, but :

”ISO 2320 applies to lock nuts with nylon inserts within the temperature range of −50 °C to +120 °C.”

... and there are some usefully defined terms, which might inform this discussion:

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**LINK**

https://amesweb.info/Fasteners/Metric_Hex_Nuts/Prevailing-Torque-Values-Lock-Nuts.aspx

MichaelG.

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Edit: __ also see this : https://nylok.com/fastener-glossary

Edited By Michael Gilligan on 06/06/2021 06:08:46

Stick it in the lathe and bore the nylon out slightly this will still leave some thread but the amount of contact area will be reduced and therefore friction. You can take a bit off and try it then take a bit more if needed.

Run the nut up and down the thread with a power tool. That ought to loosen it a bit.

+1 for run it up and down a bolt it will soon loose its grip. That is why repeated use of nylocs should be avoided.

If you can get a drill into where the nut is.

Tighten either a standard nut or a nyloc with the nylon cooked out of it. Drill through a nut flank into the bolt, that is sometimes enough to hold it without putting wire into the hole.

Hi all - Problem now sorted thanks to the combined advice given on the topic. The answer was a combination of running the nut up and down the bolt a number of times plus a modified 2-pin wrench to provide greater leverage. Surprising thing is that although the torque level is now at an acceptable value for the job in hand, there is still a fair degree of stiffness retained in the nut. Thanks to all who responded.

Try drying the nut in a warm oven for a few hours.

It will shrink, by an amount depending on the humidity it's been stored in, and it may be easier for the screw to compress it.

As it reabsorbs moisture, it will regain its grip.

Neil

I have used blunt taps and also a length of studding, an electric drill with reverse, a ring spanner, and bingo, the nut is not quite as stiff.

+1 on Jason B's method.

Would a plain nut and spring washer not be a simpler and more elegant solution?