Difference between nyloc lock nut & all metal lock nut? 9

[var10]

Hey guys

I am trying to know how an all metal lock nut works? Is it similar to nyloc nut where instead of a nylon strip inside the metal works to hold the fastener during vibrations?

 

[Tmoose]

I'd say either type is of limited value keeping a nut tight under the influence of vibration. Much better is to design the joint with fasteners using appropriate preload and sufficient grip length, and install them correctly.

But yes, both types cause material to be deformed to create a prevailing fairly small prevaiing torque.

 

[moltenmetal]

I was going to make the smart-@ss comment that the difference is that the Nyloc ones actually work- at least at keeping the nut on, if not keeping the bolted joint tight- whereas the various types of lock washers etc. don't seem to.

Something else that works is post-assembly threadlocker. Works even with teflon coated fasteners- mind you, you usually have to throw them away after dissembly as the teflon coating tends to come away from the surface of the fastener.

 

[kingnero]

Depending on the application, you might want to consider Nord-lock.
I've always considers Nyloc nuts for "home applications" (eg. not-critical), but that's just my opinion.

 

[NickE]

Some prevailing torque lock-nuts can be pinned or safety wired. However once you've lost the pre-load the joint has essentially failed.

Nick

 

[MintJulep]

Both Nylon element and all-metal prevailing torque nuts work by elastic deformation of a portion of the nut against the male thread.

For the Nylon element nut the deformation is caused by the male thread impressing into the Nylon as the Nylon passes over the male thread.

For an all-metal element the nut's thread is typically manufactured either slightly out-of-round or under size, necessitating elastic deformation of the nut as it's threaded onto the male thread.

The operational principle of both is that the interference fit prevents relative lateral movement in the threads - that is movement perpendicular to the thread axis, Lateral movement is a contributor to loosening under vibration.

Depending on what you read and believe, the Nylon element may also provide some damping.

Nylon element nuts have temperature limitations.

All-metal versions may cause galling, or may damage coatings.

 

[DerbyLoco]

Our customers demand a wide varity of secondary retention of bolted joints including Nylock, Vargal, Nordlock and the more conventional bent beam types plus even split pins. This can be on the same product so we get a direct in service comparison. Regardless of the type specified well engineered joints don't fail and stuff does not fall off despite a very sever enviroment. We always call for new nuts every time except for some of the very expensive types but then the number of re-uses is strictly controlled.

 

[drawoh]

I like the MS21043 series ring based nuts, which are all metal and self locking. I think you can re-use the nut a few times. I am not so sure of the screw you use with it.

I try very hard to not use self locking fasteners because I want to use torque to control clamping force. On a regular non-locking fastener, 90% of your torque is friction. It is difficult to know exactly when you have just barely snugged the joint, so turn of screw methods do not work either.

--
JHG

 

[hydtools]

I gave MintJulep a star for answering the asked question rather than stating a preference or alternative to a lock nut of any kind.

Ted

 

[tbuelna]

I gave MintJulep a star for answering the asked question rather than stating a preference or alternative to a lock nut of any kind.

That's a good thing to remember when posting answers to questions.

Of course, based on the specific question posed in the OP it would seem that var10 may not have a full appreciation of the effects of vibration on joints using threaded fasteners like locknuts. Thus, besides simply providing an explanation of how a plastic locking element functions in a locknut, it would seem helpful to elaborate on how vibration affects threaded fasteners in general and what type of fastener might be appropriate for a specific application. By adding relevant comments that are somewhat beyond the scope of the original question, it can prod the person asking the question to think more deeply about the issue on their own. The best replies I have read on these forums are the ones that provide guidance on how the poster can resolve an issue on their own, and ideally become better engineers/designers in the process.

Regards,
Terry

 

[Tmoose]

I agree MJulep's answer was a very good one, but OP's query included the stipulation he was trying to "hold the fastener during vibrations."

 

[var10]

Thank you everyone. Now I have a descent understanding about them. Also great ideas from everyone.

I had a look at thread locker and nor-lock. I am not sure how hard it will be to disassemble when you use a thread locker and nor-lock clinches two materials if my understanding was right. I want them to be easy to disassemble to provide easy access during repair.

I am also wondering how will the use of clinch fasteners change the overall design. Its only during the testing stage that I need to be concerned about vibrations but in reality there will be a lot less vibrations. And I think clinch nuts can easily withstand this amount of vibrations.

The only problem with clinch nuts are that they can not be installed at tight corners and closed gaps as they require a press (and this is hard to achieve when we receive parts after machining and folding as we do not do them in house). It would be very cool if someone comes up with hand held clinch nut press machine.

Thanks,

 

[moltenmetal]

Threadlocker adhesives come in various strengths. The post-assembly "wicking grade" stuff is pretty strong but definitely possible to disassemble.

 

[KENAT]

Regarding threadlock, I had our loctite rep in a couple of months talking various things over and one thing that came up is that the typical loctite thread locks aren't really intended for used with 'non reactive metals' (I think that was the term he used) like stainless steel & aluminum. Now I have some anecdotal evidence that they do work at least to some extent with those materials but I just thought I'd throw that tid-bit out there.

There are a bunch of different grades of thread lock too, the low strength ones will typically give you protection from vibration shaking things loose while allowing for fairly easy disassembly. Obviously there are other factors that play in though so don't take this as gospel.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[drawoh]

KENAT,

We use the 242 medium strength threadlocker on our stuff, which mostly is aluminium, with stainless steel fasteners. It works fine.

When we use the very high strength shaft retaining compounds, we use their primer to prepare the surfaces of the aluminium and stainless steel parts. This works very well.

--
JHG

 

[KENAT]

drawoh - I've sheared SST screws thread locked into aluminum when trying to remove them so yeah it certainly works to some extent!

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[dgallup]

There are activators you can use for the "non-reactive" materials.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[hydtools]

The Loctite thread adhesives need a copper ion to activate. If the threaded parts have copper in them, the thread adhesive will react. Otherwise an activator must be used.

Ted

 

[CoryPad]

Loctite's thread adhesives are anaerobic acrylates with peroxide initiators. They do not need copper, although it is particularly active. Iron has sufficient activity for these adhesives.

 

[tbuelna]

var10- Adhesive thread locking compounds and plastic thread locking elements each have pros & cons. But either type can do a satisfactory job of preventing a nut from loosening under most vibration conditions if used properly.

The plastic element produces a prevailing torque effect by creating an interference fit with the mating thread flanks. However, the prevailing torque effect diminishes over time due to creep/relaxation in the plastic locking element material. Adhesive thread locking compounds create a prevailing torque effect by bonding together the mating thread flank surfaces. This prevailing torque effect is normally consistent over time.

One other major difference between the two locking methods has to do with quality assurance procedures. With the nyloc, it is easy to verify proper function of the thread lock by measuring the prevailing torque at each installation. This is not possible with adhesive thread locking compounds since the prevailing torque effect is not present until after the adhesive compound cures, and then the only way to verify its capability would be to break the adhesive bond. Thus, quality assurance when using thread locking compounds is entirely dependent upon careful process control.

Hope that helps.
Terry