Nyloc Nut vs Plain Nut

The principle behind this type of nut is that there is always a source of friction between the nut and the thread it is screwed on to, being provided by the nylon insert in the head of the nut.

A plain nut, should it shake loose, incurs the possibility of it unwinding fully from the screw and falling off, with a consequent risk of self-disassembly of the parts it is holdng together. A nylock nut stands a better chance of remaining on the thread, thereby reducing the risk of self-disassembly and possibly giving an audible warning of the situation before a failure occurs.

Other options:

• Second nut as a lock-nut
• Shake-proof washer
• Nord-Lock washers

require more parts, and there is always a risk of losing the parts or not fitting them on re-assembly after maintenance activities. This possibility does not occur with the nylock nut.

Beware of installing nylon-containing parts anywhere there is a risk of hydrochloric acid [HCl] or hydrogen chloride vapours being present: HCl 'digests' the C=O to NH groups present in nylon every six carbon atoms and breaks it down, by the same process that proteins are hydrolysed to amino-acids by HCl in the stomach. Nylon will give poor performance as a result. It is common practice to use PVC cable ties, instead of nylon ones, in water treatment plants containing regenerable ion exchange resins for this very reason where the resins are regenerated by HCl.

If you have the budget, try FLEXLOC nuts from UMBRAKO.

Don't use Nylon insert nuts in high heat applications, either.

Loctite works for me, and there are different strengths to suit the application. Much cheaper.

RED loctite if you NEVER want to take it apart... also known as stud locker.

BLUE if you might need to take it apart next year...

and there is a 3rd, which color I don't remember, but with less holding power.

Another option used in aeronautics, is to use safety wire. Drill a hole through the "bolt" just above the top side of the nut, run a piece of safety wire through the hole, and tie the safety wire to itself... or other bolts... to prevent the nut(s) from unthreading themselves. I believe safety wire is stainless steel, but I don't know.

In any case, Nyloc is a locking nut. The lesser option is to use a second nut as a lock nut. Something else to know about Nyloc's is that once you remove them, they no longer have the locking capability, and must be replaced with new.

Another option is Kem-nuts. They have a star washer incorporated with the nut... which locks the nut in place.

The fact you can't yse them again is a very important one. It is very tempting to stick the Nyloc back on again but when I worked with wind generators I actually saw a blade fly off a generator because the Nylocs were used twice and didn't hold. From then on it was red Loctite but as you say it is a bugger to get the nuts off once you use this stuff. Mostly you will break the bolt.

If you are using relatively big bolts and nuts(20mm and above)I would be inclined to drill a hole in the bolt and use a split pin. Once again though, if you use a split pin always throw it away after one use and get a new one.

One other thing about Nylocs. It's not a major problem but if you have hundreds of nuts then it can be very time consuming unscrewing them if all you have is a spanner. I had to undo 120 by hand on a wind generator and it was like chinese water torture cos you can't spin em off.

if posible most thread lock compounds can be loosen with heat some that the nut comes free.

Thanks, useful to know for the future. Thing is I now work in the aquaculture industry and very rarely use thread lock as most of the time nuts rust onto bolts so we have the other problem. Not keeping nuts on but how to get the bloody things off when they have been submersed in seawater for years.

Heat again, just like with old car bolts - the heat affects the rust, allowing easier removal.

Penetrative products like "Rust Buster" work ok on rusted bolts on cars, not sure how well it would work in a marine environment though.

For those extra stubborn, rusted on fixings, theres only one product to use - diesel oil!

Try Loctite Silver or Nickel Anti-Seize. I use it in underground conditions in a mine with highly acidic groundwater. I also use it at home for bolts on my boat trailer and bolts and nuts used in my outboard motor.

1- there are books about fasteners and there you find a lot of informations. It depends on your language since many of them are not written in English. Look by amazon for j.h.bickford as author name.

2- "+" the principle to make an assembly safe is to introduce a friction remnant torque independent of the pre loading in the bolt. Washers have a torque which is directly related to the pre load and thus ineffective under hard conditions. Nylock generate a friction torque proportional to the nylon compression which is function of the thread geometry and the nylon insert. the only problem is that nylon has a tendency to creep so that the initial torque gets lower over time. never the less it is a good solution provided that the ambient temperature is not too high. Attention to what was mentionned in other comments loctite presents the same behavior in a higher temp range so that pay attention.

3- "-" were mentioned :

-chemical sensitivity

-since the friction torque does not depend on pre loading to un tighten them you need to fight against even when the pre load is nil.

-when the bolt is tightened ther is a relationship between torque and pre load. If one is using a Nylock nut the friction torque of the nylon insert MUST be taken into consideration if not the bolt is not correctly preloaded and can fail under load. Un fortunately too many times this aspect is totally neglected and surprises do appear.

One of the participants mentioned the nuts from umbrako they are good but not the only possibility. Any way if you have the money for it you will better be served by a nut with an elastic (metal) "brake".

Hope you got the answer you expected

Depending on the size of the bolt and space there are castle bolts availble.

They are retained with a cotter pin.

I agree on the use of Loctite and heat. We have occasion to use RED Loctite around the shop at times and applying a little heat with the torch allows us to back the bolts out/remove the nuts fairly easily. We don't have any applications where we have a bad vibration problem so I don't know how Loctite would be in that situation.

Like one poster stated with nyloc nuts: it pretty much requires the same torque to install or remove the total distance vs. breaking a normal nut loose and then just spinning it off.

I would try nyloc nuts in your application and keep an eye on them for a while, they may work just fine for you.

One thing to think of Nylon become brittle at low temperatures does not do well in sunlight and will with time age and become less elastic. Don't over torque them.

Correct, but this can be to the user's advantage.

These nuts are used to hold together the steering and suspension parts on cars, and the ageing helps them to hold better. As they cannot (well should not) be re-used, localised heat on the nylon melts it out of the way, so easing removal. Where the nylon has got to the stage of cracking, it still aids retention, but can be removed prior to turning the nut by inserting a small screwdriver into the cracks, and levering the pieces out.

Ok but what if your product or use requires prolonged exposure to very low temperatures? Also what is there will be strong UV radiation such as in the antarctic?

You know what they say location is everything.

Once again, our guest has provided the minimum information, so we are left to guess the usage of the component. Vibration was mentioned, excessive cold was not: maybe it's for use on the space shuttle, as an alternative to the 'O'rings.

Try "Spiralock"

if you have the budget. These nuts have a unique female thread form with a ramp which interacts with the standard male thread form. These were used on Turbocharger nose-nuts and certainly do not become loose under any conditions.

Dear all,

Please help me.

Some people above mentioned that, once removed the nyloc nut no longer retain its locking capacity and must be replaced with a new one.

Does anybody know where this statement originally came from? Word of mouth, engineer's experiences, or is it defined in a book or official document?

Thanks!

Please advise if you received cofimation that this statement is correct. As far as we know nyloc nuts can be re-used.

Dear All,

we are planning to replace plain Hex nut with Nyloc Nut. After tightening of Nyloc Nut using DC Nutrunner, retained torque using dial type torque is coming just half-of the torque applied using NR. this not happening with plin nut.

is there is any major torque loss if we use Nyloc nut using DC Nutrunner.

Regards,

Reddy P C

A Nyloc nut can be used one or maximum two times. Since it is 'cutting' into the bolt, it might become unusable. So, for smaller sizes, it is better to use self locking nut i.e. nuts with elliptically deformation or crimped nut. These types will be retaining the locking feature even after 15 cycles of use. However, initial torque needed will be more than that is required for Nyloc nuts.

Dear Guest,

I wish to reply as follows.

The NYLOCK NUT to be tightened in such a way, only LESS THAN 1/4th thread of the bolt is exposed or protrudes out from nut. The length of the Bolt plays a vital role for the life of Nylock nut and its REPEATED USAGE. I have used same Nut more than 20 times. There should not be any heat addition to the bolt nut after tightening. Any heat addition, the property of Nylon is lost.

The philosophy adopted here is that as long as the Nylon Ring does not loose its elasticity and undergoes moderate compression, the PHILOSOPHY of NYLOCKING IS VALID. To achieve this we should select Bolt Length as JOB HEIGHT+NUT HEIGHT+ PITCH OF THE THREAD of the Bolt.

During first time using the nut should be tightened in such a way, after applying the required Torque, the Bolt should cross the nut less than 1/4th thread of bolt or pitch. This guidance will keep the elasticity with in limit and shall not undergo full compression.

In course of repeated usage, tightening of Nut to be limited in such a way that the bolt does not cross the nut by more than pitch and as long as this is maintained using of the same nut number of times will be more.

The above explanation holds good for the comment No. 21, in this thread by another Guest.

Thanks,

DHAYANANDHAN.S, INDIA.