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Why not more Nord-Lock washers?

wjb

Well Known Member
I've been wondering for some time why Nord-lock type washers are not used on our birds. They have a neat design that uses tension in the washer to rather than friction in the locking nut to provide the locking action. They are touted to be particularly good in high vibration environments. Interesting video here: https://www.youtube.com/watch?v=IKwWu2w1gGk

I finally came across a set in my Matco brakes; the AN4 bolts that hold the pad opposite the plunger have Nord-like type washers. It's a bolt into a blind hole, so safety wire or Nord-locks are the only way to secure them.

My question to the VAF brain trust: Why aren't these washers used more frequently? On my IO-360, all the bolts use the ancient star washers as "lock washers." It sure seems they get smashed down pretty flat after one use. Is it the price?, love of pre Wright bro's technology, or some other reason(s)?
 
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I've been wondering for some time why Nord-lock type washers are not used on our birds. They have a neat design that uses tension in the washer to rather than friction in the locking nut to provide the locking action. They are touted to be particularly good in high vibration environments. Interesting video here: https://www.youtube.com/watch?v=IKwWu2w1gGk

I finally came across a set in my Matco brakes; the AN4 bolts that hold the pad opposite the plunger have Nord-like type washers. It's a bolt into a blind hole, so safety wire or Nord-locks are the only way to secure them.

My question to the VAF brain trust: Why aren't these washers used more frequently? On my IO-360, all the bolts use the ancient star washers as "lock washers." It sure seems they get smashed down pretty flat after one use. Is it the price?, love of pre Wright bro's technology, or some other reason(s)?

Star washers are to be used only one time, then tossed. They are also cheaper.
 
I used Nord washers at the recommendation of B&C to mount my B&C starter to my IO-360. I replaced a broken SkyTec.

Cool video. Thanks
 
because they weren't around 50 or 70 years ago when the conventions were set. If you haven't noticed, aviation folks are some of the most resistant to change that I have ever met. I suspect much stems from the regulatory issues. We still frown on people that have moved on from the tractor mags that we call "aviation grade."

Larry
 
They work really well

A colleague of mine coined the acronym NDS meaning: New, Diferent, Scary. It describes well the engineering world (not just aviation). Why we don?t use them... perhaps institutional momentum, but I can attest that nordlocks work and they work very well. These days I design systems that go into some of the most severe vibration environments around (high temperatures, with repeated short-duration accelerations well above 1000g) and nordlocks are our go-to. What we design are system-critical components where a failure can have life-ending consequences and I?ll sometime need to stand next to the thing while it?s operating so you bet your backside the nordlocks better work. I don?t ever trust promotional stuff about products, but in this case they work.
 
After watching the video it looks like they damage the material being clamped. Would they still work if there was a flat washer under them?
 
We use these on our Sno-Cat track tension lock nuts, 1" dia. extremely difficult to loosen. Yes, they work!
 
before nordlock washers jabiru required that the flywheel attach bolts be removed, cleaned and retorqued with thread locker. now the approved method of securing those bolts is with nordlock washers.
fwiw that was still probably a 4 hour job as dynamo bracket had to be removed along with coils which had to be reset. then a builder came along and drilled a hole in the bracket to access the bolts with an allen wrench as the engine was turned over. literally went from a half day job to 10 minutes.
 
No wait a second

If you notice, in the fixture used, the bolt to moves transverse a fair amount. To me this means that the bolt hole is significantly larger than the bolt shank. This will obviously allow the bolt to walk in the hole, moving the nut.

Where on our planes do we tolerate over sized holes or undersized bolts? No where.

Not saying nordlocs are bad, just saying that this test is biased.
 
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What about Nord-Lock washers instead of safety wire for the fillister head screws on Van's gascolator? Any opinions?
 
If you notice, in the fixture used, the bolt to moves transverse a fair amount. To me this means that the bolt hole is significantly larger than the bolt shank. This will obviously allow the bolt to walk in the hole, moving the nut.

Where on our planes do we tolerate over sized holes or undersized bolts? No where.

Not saying nordlocs are bad, just saying that this test is biased.

I think that's the whole point of the test. It's like that for all of the options hence why they get loose and the Nord washer uses the same fixture. In my opinion this test is not bias at all. It's actually pretty darn impressive :D
 
COST $$. At Aircraft Spruce MS35333 cad plated internal tooth #10 washers are $.02 each. Same size Nord Lock is $.55. Nord Locks lock better than interrrnal or external tooth lock washers. It seems like the only thing that is as secure as a Nord Lock that is commonly used is safety wire or safety cable.
 
The prop bolts for the Sensenich GA composite props use Nord-Locks on them.
The manufacturer says to re-torque after 100 hours and I've never had one get loosened up at all.
 
The prop bolts for the Sensenich GA composite props use Nord-Locks on them.
The manufacturer says to re-torque after 100 hours and I've never had one get loosened up at all.

Are you saying you use Nord-Locks in place of safety wire? Im not judging here. I would love to use Nord-Locks instead of fighting the safety wire installation on my Whirlwind 200RV prop.

erich
 
If you notice, in the fixture used, the bolt to moves transverse a fair amount. To me this means that the bolt hole is significantly larger than the bolt shank. This will obviously allow the bolt to walk in the hole, moving the nut.

Where on our planes do we tolerate over sized holes or undersized bolts? No where.

Not saying nordlocs are bad, just saying that this test is biased.

Very good point..... I would like to see how well the standard lock washers would hold up to this test with proper bolt installation.

There are places on the aircraft that would benefit from using nordlocks, but they are very few and therefore would justify the extra cost, like the starter.
 
Are you saying you use Nord-Locks in place of safety wire? Im not judging here. I would love to use Nord-Locks instead of fighting the safety wire installation on my Whirlwind 200RV prop.

erich

On the RV-12 Sensenich GA prop, yes. Nord-Loc washers, no safety wire. I have never found a bolt that wasn't as tight as it should have been.
 
COST $$. At Aircraft Spruce MS35333 cad plated internal tooth #10 washers are $.02 each. Same size Nord Lock is $.55.
So you won't use the best available lock washer in order to save 53 cents? :rolleyes:

On my plane, I use Nord Locks to secure the prop extension onto the crankshaft, the prop bolts onto the extension, and on the Matco brake discs and pucks. No safety wire.
 
The Matco calipers and rotor use them on our RV10. The Whirlwind Razor, 3 blade prop on my 912ULS powered Highlander specifies Nord-Lock. Never had one loosen up.

Gary
 
After watching the video it looks like they damage the material being clamped. Would they still work if there was a flat washer under them?

Would not be used at my company due to damage to the underlying material and corrosion protection coating under the head. The video touted that damage as proof it is working. My strength engineers would call that stress risers infinitely worse than a none deberred hole.

It has its special uses but not to replace standard locking methods.
 
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So you won't use the best available lock washer in order to save 53 cents? :rolleyes:

Yes, I would definitely use a Nord-lock in place of safety wire, and $.53 wouldn?t stop me. There are many places I can do this and therefore have ordered a supply of Nord-locks. The one place that would be most beneficial is my prop installation. Unfortunately, I would have to remove the installed prop to do this, and then I would have to remove the roll pins holding the nut to the threaded stud, install the Nord-lock, then reinstall the pin. I may do this if I have to remove the prop, but for now, what?s the point? I was just pointing out the price differential that someone else mentioned, and that may have something to do with why Nord-locks haven?t been universally accepted.
 
One nice upgrade on the new Jabiru 2200/3300 generation 4 engines, nord-lock washers are used throughout the assembly.
 
On the RV-12 Sensenich GA prop, yes. Nord-Loc washers, no safety wire. I have never found a bolt that wasn't as tight as it should have been.

Yes, just I was just following the manufacturer's instruction on installation of the prop and hub.

I would definitely seek their (Whirlwind's) approval if you deviate from using safety wire that they recommend.
 
I've been wondering for some time why Nord-lock type washers are not used on our birds. They have a neat design that uses tension in the washer to rather than friction in the locking nut to provide the locking action. They are touted to be particularly good in high vibration environments. Interesting video here: https://www.youtube.com/watch?v=IKwWu2w1gGk

I finally came across a set in my Matco brakes; the AN4 bolts that hold the pad opposite the plunger have Nord-like type washers. It's a bolt into a blind hole, so safety wire or Nord-locks are the only way to secure them.

My question to the VAF brain trust: Why aren't these washers used more frequently? On my IO-360, all the bolts use the ancient star washers as "lock washers." It sure seems they get smashed down pretty flat after one use. Is it the price?, love of pre Wright bro's technology, or some other reason(s)?

One reason: what problem are people experiencing that would these solve? I mark every nyloc type of nut with torque seal, and have never seen any rotation in 1650 hours. Damaging the underlying material would seem to be a net negative of a Nord-Lock (besides price).
 
One reason: what problem are people experiencing that would these solve? I mark every nyloc type of nut with torque seal, and have never seen any rotation in 1650 hours. Damaging the underlying material would seem to be a net negative of a Nord-Lock (besides price).

Nord locks seem to provide additional security against loosening compared to other washer and nut solutions and are far easier and less time consuming than safety wire, which can be a real bear in some cases, like on my Whirlwind prop. The cost differential is so minimal it?s not really a factor. I agree the surface damage is a drawback, but perhaps tolerable in many cases since it?s not visible when the hardware is installed. I have a hard time seeing how the slight surface damage is a structural concern when the area under the nut and washers is being compressed significantly.

Erich
 
Nord locks seem to provide additional security against loosening compared to other washer and nut solutions and are far easier and less time consuming than safety wire, which can be a real bear in some cases, like on my Whirlwind prop. The cost differential is so minimal it?s not really a factor. I agree the surface damage is a drawback, but perhaps tolerable in many cases since it?s not visible when the hardware is installed. I have a hard time seeing how the slight surface damage is a structural concern when the area under the nut and washers is being compressed significantly.

Erich

If you have an application where Nord Locks are specifically called out by the manufacturer, they have probably engineered their use, and are good with them. My concern (along with others that have mentioned it) is the surface damage. It?s probably ok to ding the casting on a train bogey, but airplane parts are much thinner and lighter, so I?d be nervous about randomly using them where you might take a significant portion of the original part thickness. Prop bolts? You?re probably dealing with plenty of meat. Baffle attachments (for example)? Not so much....

So I know they have their place, but there are reasons to ask some questions about using them just anywhere (or everywhere) - which I think was the original question.

Paul
 
true...

Definitely ask questions...

That being said, there are quite a few replies on "surface damage". While it is true that the Nord Locks will engage the surface, it is ALSO true that internal and external toothed lock washers, as well as a standard lock washer will engage the surface, too; that's the point...to prevent rotation of the fastener.

There could also be an entire discussion about the engineering aspects of using a flat washer beneath the lock washer...it just depends how far you want to take it.
 
One reason: what problem are people experiencing that would these solve? I mark every nyloc type of nut with torque seal, and have never seen any rotation in 1650 hours. Damaging the underlying material would seem to be a net negative of a Nord-Lock (besides price).

Great question!! What are we trying to fix and why spend so much doing it?
 
My fix of sorts

Great question!! What are we trying to fix and why spend so much doing it?

As much of an advocate for nordlocks as I am, they are just another tool in our arsenal, not the snake-oil elixir I wish they were. But for specific circumstances they are my first choice. In hot environments where nylon or other locking compounds can?t be used... combined with difficult-to-access areas where safety wire/cable aren?t practical, nordlocks fit the bill. They work much better than star or split washers at holding fasteners, so for me that?s the issue I?m trying to ?fix?, I like having another tool in the box that I can apply to the problems in front of me
 
Saber recommends them for some of their prop extensions (I have them on one of their older extensions where the head of the bolt recesses into the extension so you can't safety wire the head and the bolt goes into a threaded drive lug on the prop flange so no option for a locknut). I was impressed with the way they work and will certainly use some again if I have another application that needs something better than a standard lock washer but can not use safety wire or a lock nut.

One thing to keep in mind is that since they dig in a bit they create stress points that can lead to cracks. You won't have to worry about a crack developing in the bolt hole of a 2 inch thick prop spacer, but using them in something like thin wing attach fittings that are loaded in tension could have disastrous consequences.
 
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I'm always on the look out for new fastener options, and these look interesting. The idea of the washers digging into the surface they are against seems like it could definitely cause issues in some cases.

I'm wondering if a thin "sacrificial" plate could be put under the Nord-Locks where there are 2 or more adjacent fasteners. This could work in the same way that safety wire secures two fasteners. Complex shapes could easily be cut with a laser or similar for various applications.

Is there any reason that this might interfere with the proper functioning of the Nord-Lock?
 
I'm wondering if a thin "sacrificial" plate could be put under the Nord-Locks where there are 2 or more adjacent fasteners.

Is there any reason that this might interfere with the proper functioning of the Nord-Lock?

Seems reasonable as long it is impossible for the sacrificial plate to spin, which is what I think you are suggesting here.

Erich
 
Seems reasonable as long it is impossible for the sacrificial plate to spin, which is what I think you are suggesting here.

Erich

Yes, that's what I had in mind. If two or more adjacent fasteners went through a common joiner plate it should keep it from rotating. Choosing the right material hardness and plate design for the specific application might require some engineering analysis.

One issue I can think of is weight. If fasteners are far apart, this could be impractical. Also, if a hard (heavy) material is needed, safety wire would be hard to beat :)
 
which...

Yes, that discussion is what I was referring to in a previous post. The whole point of a lock washer is to prevent fastener rotation, yet most people will use a flat washer beneath the lock washer. This has the effect of the above stated "sacrificial plate" but is not constrained. So you may be back where you started without the lock washer. You are effectively "locking" your fastener to a flat washer that can rotate...same as if you had not used a lock washer...

It is an interesting engineering exercise...
 
Hard base materials

if a hard (heavy) material is needed, safety wire would be hard to beat :)

I know it?s outside the point you were making, but an important consideration when using nordlocks is that you have to be carful using hard materials under nordlocks. If the nordlock can?t engage the material under it, it won?t lock the fastener. That is, the nordlock needs to be harder than the material under it to work.

Dan
 
I know it’s outside the point you were making, but an important consideration when using nordlocks is that you have to be carful using hard materials under nordlocks. If the nordlock can’t engage the material under it, it won’t lock the fastener. That is, the nordlock needs to be harder than the material under it to work.

Dan

Good point Dan. I should have clarified my reason for mentioning harder materials. To save weight, aluminum would seem like a good candidate. It's also soft enough for the Nord-Lock to dig into easily.

I was thinking there may be some situations where it's too soft though. Or it may have poor fatigue characteristics for some types of loads. maybe a low carbon steel would be a better choice. Hard to know without the specifics of an application. That would be where the engineering analysis comes in. Your point about not being as hard as the Nord-Lock is good to point out though.

As Bob said, "interesting engineering exercise"
 
and...

Realize that what you are saying applies to ANY lock washer, not just Nord type. If the substrate is harder than the lock washer, the washer will not do it's job.

In our hobby, it is normally not an issue as most of the washers are steel or bronze and the substrate is, most of the time, aluminum.

Looking at the Nord website, you can see that they DO NOT recommend a flat washer beneath the Nord washer, as it defeat the purpose of the lock washer...

https://www.nord-lock.com/nord-lock/products/washers/product-guides/

Also, if you look at the mcmaster website, it lists wedge lock washers with a hardness of C46. A typical grade 5 bolt is about C25, and a grade 8 bolt is about C33. Point is, those washers are going to be harder than most of the metals we use in our planes...
 
I agree Bob about not putting a flat washer under the Nord-Lock, or any other locking washer. I think we're on the same page, but just to clarify for anyone that might have missed what I was describing, here's a visual:
2470-lrg.jpg

The sacrificial joiner plate keeps the rotation you are describing from happening. It also avoids damage to the underlying structure. As discussed earlier, it would have it's pros and cons though.

This horse may be dead:)
 
One reason: what problem are people experiencing that would these solve? I mark every nyloc type of nut with torque seal, and have never seen any rotation in 1650 hours. Damaging the underlying material would seem to be a net negative of a Nord-Lock (besides price).

Still the best question of this thread. Do people have fasteners on their RV loosening all the time? 13 years and 850 hours and have not had an issue with nuts becoming loose. Using as appropriate, Locknuts, safety wire, cotter pins work great. Sure there are lots of ways to ensure a nut does not loosen, but why use them if there is no issue.
 
Still the best question of this thread. Do people have fasteners on their RV loosening all the time? 13 years and 850 hours and have not had an issue with nuts becoming loose. Using as appropriate, Locknuts, safety wire, cotter pins work great. Sure there are lots of ways to ensure a nut does not loosen, but why use them if there is no issue.

Previously asked and answered. Safety wiring can be difficult and time consuming in certain situations. Two examples: engine driven fuel pumps and whirlwind props.

Yes, the horse is dead.
 
Previously asked and answered. Safety wiring can be difficult and time consuming in certain situations. Two examples: engine driven fuel pumps and whirlwind props.

Yes, the horse is dead.

That is the answer to if there are potential uses for nordlocks. Sure there are. The question I asked is if there are places on an RV that traditional locking fasteners are not working properly and loosening. Valid question to this forum, not answered, horse not dead.
 
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I have found a place to use them

I have had screws holding my baffles to the cylinders - which used external tooth washers - come loose and fall off. I put Nord-Lock washers on these and since I did this no more lost screws.
 
What makes one think these are BETTER? Ad hype... proof?

What makes one think that lock washers or star washers don't work?

A few reasons for not using the newest lock washer.
1) Inertia - In aviation to test, certify new things is a big deal, experimental feel free use.
2) Thickness - It looks like more stack-up, adds weight and total height to installations.
3) Cost - Looks more expensive.

None of these reasons have anything to do with being better or not in keeping bolts and nuts from backing out.

Regardless of washer type, things stay tight due to FRICTION. Washers can add friction. Not sure if this new design is better,
just different. It looks fancy. However it is not new. I have seen variations of this, with just a single washer.

Locktite is another method (works, light, cheap).

Many applications, including Jet Engines and car engine head bolts come to mind, use "stretch" bolts...
They are torqued up very high, then turned more to stretch the bolt. They in a word are so tight they
will not back off. As bolt is put under load, parts expand and contract, the bolts will stay torqued even
if the pre-stress or stretch is partly relieved. No lock washer, safety wire or locktite is needed or wanted.
In case of a jet engine there are so many nuts and bolts safety wire would be a nightmare.
 
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Hmm...

Nord Lock has been around for a long time, and the wedge lock washers have specific uses. In these applications, yes, they ARE better. Specifically, they have a much greater locking force than standard lock washers and even internal/external tooth lock washers. They have proven themselves in extreme vibration and dynamic loading situations.

That said, using them where they aren't really necessary is likely a waste. As stated, they are somewhat thicker, marginally heavier, and definitely more expensive.

They can be an alternative where safety wire isn't feasible, or additional locking capability is warranted. For example, they are used on the Match brakes for the -10.
 
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