Best Lock Washers

[Lumpy Idle]

just stumbled across this on the intertoobz and thought it would be of interest to listees. BTW, if you also own a harley this viddy should be of special interest.

https://www.youtube.com/watch?v=ZSOjxU3pdSU

[pyoungbl]

Although he is pimping stuff he got for free....he's also totally correct.  If you really do want to keep the bolt/nut from vibrating free the answer is NordLock.  They are expensive but can be used over and over.  I got some in 6mm, 8mm and 10mm which should last me a lifetime since I only use them in critical spots.

[canuck750]

Agreed, they are expensive and you are supposed to use them in the pairs that they come in (not separate them to use individually).

[Kiwi_Roy]

Aren't they sold as Schnorr washers for our Guzzis?
Here we go from MG Cycle
Lock washer, 8mm internal diameter, cone shaped, serrated, and hardened spring type lock washer. Commonly replaces fold over lock tabs, used in many applications over many models and years. This washer is most commonly used to attach the flywheel to the crankshaft and is used in other similar situations. Alternate number 976484
 
They sure do work well, I tried one using a torque wrench, don't ask me what I found but I was impressed.

[kirkemon]

Save $ on Loctite

[Lannis]

I started worrying about all the $$ signs, so I looked them up on McMaster Carr.

In common sizes around 1/2" or 13mm, they're about $2 each.   Not too bad but you wouldn't want to use them everywhere.

I must say, though, that I've never had a NyLok nut come loose on any of my old British bikes, although for a blind bolt into a casting, these Nord Locks seem like they'd really do the job.

Lannis

[Chuck in Indiana]

They are just the ticket for doing the "rear drive mod" on the old small blocks. No worry about those suckers ever backing out.

[Moto]

Aren't they sold as Schnorr washers for our Guzzis?
...

No, the Nord-Locks are like Schnorrs split in two, with a clever ramp arrangement machined into the separate halves. The effect of the ramps is to move the two halves apart when an unscrewing torque is applied, further increasing the clamping pressure, it seems.

You can see comparative photos here, on pp. 23-24:

http://www.crossmanufacturing.com/pdf/spiralock/fastener-vibration-testing.pdf

I wonder how much improvement this provides over the simpler Schnorr design.

Moto

[Lannis]

No, the Nord-Locks are like Schnorrs split in two, with a clever ramp arrangement machined into the separate halves. The effect of the ramps is to move the two halves apart when an unscrewing torque is applied, further increasing the clamping pressure, it seems.

You can see comparative photos here, on pp. 23-24:

http://www.crossmanufacturing.com/pdf/spiralock/fastener-vibration-testing.pdf

I wonder how much improvement this provides over the simpler Schnorr design.

Moto

I wondered too, because both designs depend on the serrated surfaces (not the ramps but the others) gripping the steel of the bolt and of the surface being bolted.   If either one of these slips, the ramps don't come into play.

But come to think of it, if there's ANY vibratory component of the torque acting in the un-loosening direction, which would tend to overcome the serrated grip, the ramps DO come into play, tending to make the serrations grip harder, which the Schnoor would not do.

I'm sure the designers have it figured out.   The vibrating test setup is pretty cool, and if it's typical of actual motorcycle vibration, pretty definitive ....

Lannis

[Chuck in Indiana]

the ramps DO come into play, tending to make the serrations grip harder, which the Schnoor would not do

this

[Stevex]

I started worrying about all the $$ signs, so I looked them up on McMaster Carr.

In common sizes around 1/2" or 13mm, they're about $2 each.   Not too bad but you wouldn't want to use them everywhere.

I must say, though, that I've never had a NyLok nut come loose on any of my old British bikes, although for a blind bolt into a casting, these Nord Locks seem like they'd really do the job.

Lannis

Beat me to it   

[Chuck in Indiana]

A nyloc will come loose in an aircraft engine compartment. Don't ask me how I know.. 
that's why they make high temp nuts for engine compartments and brakes.

[twhitaker]

I would be surprised if they worked on anything softer than steel.

This

[Moto]

Here are a couple of interesting pages about Nord Lock vs. serrated (e.g. Schnorr) washers.

The first is a (Nord Lock) video demonstrating clear superiority of the Nord Lock under the chosen test condition:

https://www.youtube.com/watch?v=G63ZVB229Eo

But the second is a table suggesting the Schnorr type does well under high preload:

http://www.nord-lock.com/bolted/comparing-nord-lock-x-series-with-serrated-spring-washers/

This raises the possibility the first link might be showing a dramatic difference because the preload wasn't high enough.

Probably my flywheel is just fine with its Schnorr washers, but the Nord Locks do look better.

[Stevex]

A nyloc will come loose in an aircraft engine compartment. Don't ask me how I know.. 
that's why they make high temp nuts for engine compartments and brakes.

Never, ever used Nyloc on an aircraft; either full metal self locking, castellated and split pinned or plain wirelocked.

[Chuck in Indiana]

Never, ever used Nyloc on an aircraft; either full metal self locking, castellated and split pinned or plain wirelocked.

I call BS.  The AN365 is perfectly adequate for low heat "not subject to rotation" situations.
http://www.aircraftspruce.com/catalog/hapages/locknutkit.php?recfer=4441
I see you are from England, though.. and the regulations may be different. I was spending some time with a guy that restores Tiger Moths, and he said, "I *hate* to get an aircraft from the Stites  because I *know* the maintenance will have been dreadful.." 

[Stevex]

I call BS.  The AN365 is perfectly adequate for low heat "not subject to rotation" situations.
http://www.aircraftspruce.com/catalog/hapages/locknutkit.php?recfer=4441
I see you are from England, though.. and the regulations may be different. I was spending some time with a guy that restores Tiger Moths, and he said, "I *hate* to get an aircraft from the Stites  because I *know* the maintenance will have been dreadful.." 

Call BS all you want, I've work RAF / UK military aviation since 1977; I only use Nyloc in my garage, not in the hangar.

[Rough Edge racing]

100's of millions of car/truck and many bike engines have no locking devices on connecting rods or main bearings nuts or bolts...And  head bolts...Does anyone know the reason?

[Moto]

100's of millions of car/truck and many bike engines have no locking devices on connecting rods or main bearings nuts or bolts...And  head bolts...Does anyone know the reason?

Because the load variations are axial instead of transverse, I reckon.

Here's an interesting page on that and other fastener topics:

https://engineerdog.com/2015/01/11/10-tricks-engineers-need-to-know-about-fasteners/

Moto

[Ncdan]

Maybe im the only one that watched the video and noticed the guy put the lock washer on the bolt head. As an old wrench turner on Farm equipment and basic mechanics I�ve always put the lock washer in the nut, not the bolt head!

[redhawk47]

100's of millions of car/truck and many bike engines have no locking devices on connecting rods or main bearings nuts or bolts...And  head bolts...Does anyone know the reason?

A bolt with a split ring or star lock washer will loosen sooner that a bolt with no washer.
The load is in the direction of the tension in the bolt. There is relatively little transverse load or vibration.

[redhawk47]

Maybe im the only one that watched the video and noticed the guy put the lock washer on the bolt head. As an old wrench turner on Farm equipment and basic mechanics I�ve always put the lock washer in the nut, not the bolt head!

It doesn't matter which end you put it on; if it is a split ring lock washer it will loosen in short order.
If it really did work you should have one on both ends, but actually that will cause it to fail even sooner.

[redhawk47]

Because the load variations are axial instead of transverse, I reckon.

Here's an interesting page on that and other fastener topics:

https://engineerdog.com/2015/01/11/10-tricks-engineers-need-to-know-about-fasteners/

Moto

Excellent fastener article. #11 is one to keep in mind. If you have ever had a Japanese motorcycle with engine cases attached with what looked like Phillip head screws - they are not Phillips, and #11 explains why your Phillips driver destroys the cross recess. They are JIS cross recess and require a JIS screwdriver. Many, but not all, JIS screws are marked with a dot between two arms of the cross.
A JIS screwdriver also works well in a Phillips screw. I will no longer buy Phillips screwdriver, only JIS.

[redhawk47]

Save $ on Loctite

Yes, Loctite is your friend, but it won't work on header bolts.
The way to get a Loctite joint apart is to heat it up, which breaks the bond.

[fossil]

This is interesting. I have exactly the same discussion in our company. There are Schnorr washers used through the full range of products which I simply think is wrong. First of all the Schnorr needs a lot of torque, then they are not exactly good on e.g. powdercoated surfaces. I would very much prefer NordLock, but they are expensive. And as our products are built into the engine rooms of ships NordLock would be the way to go.

[Moto]

Excellent fastener article. #11 is one to keep in mind. If you have ever had a Japanese motorcycle with engine cases attached with what looked like Phillip head screws - they are not Phillips, and #11 explains why your Phillips driver destroys the cross recess. They are JIS cross recess and require a JIS screwdriver. Many, but not all, JIS screws are marked with a dot between two arms of the cross.
A JIS screwdriver also works well in a Phillips screw. I will no longer buy Phillips screwdriver, only JIS.

Using a Phillips driver in a JIS head is also a problem, but is not what the article is referring to. It is claimed that Phillips drivers were  designed to ramp out of Phillips heads, as a torque-limiting device to prevent twisting off the heads, as I have read before and as the article says.  Endlessly frustrating, in practice. Whether this was really a design feature is in some doubt.

[Muzz]

Ya learn something every day.

I never knew that they were not Phiiilps head; having said that i use an impact driver and never seem to have had a problem. <shrug>

[redhawk47]

Using a Phillips driver in a JIS head is also a problem, but is not what the article is referring to. It is claimed that Phillips drivers were  designed to ramp out of Phillips heads, as a torque-limiting device to prevent twisting off the heads, as I have read before and as the article says.  Endlessly frustrating, in practice. Whether this was really a design feature is in some doubt.

Yes, it was a design feature. At that time torque limited screwdrivers had not been developed. Use of the Phillips drive allow full torque fastening without over-torque.
It has turned out to be a bad choice that is perpetuated out of ignorance and convenience, just like split ring helical lock washers.

[Moto]

Yes, it was a design feature. At that time torque limited screwdrivers had not been developed. Use of the Phillips drive allow full torque fastening without over-torque.
It has turned out to be a bad choice that is perpetuated out of ignorance and convenience....

Unless you were the designer, I'm surprised at your certainty. The Wikipedia article (https://en.wikipedia.org/wiki/List_of_screw_drives#Phillips) calls this a "popular belief" rather than a fact:

"The design is often criticized for its tendency to cam out at lower torque levels than other "cross head" designs. There has long been a popular belief that this was actually a deliberate feature of the design, for the purpose of assembling aluminum aircraft without overtightening the fasteners.[14]:85[15] Extensive evidence is lacking for this specific narrative, and the feature is not mentioned in the original patents.[16]"

I just read the original patent, and confirmed it does not mention such a design goal, and instead emphasizes that the intention is for the bit not to slip out.

So I call this myth busted, unless you have some new evidence of the intent of the designer.

Moto

[Moto]

A bolt with a split ring or star lock washer will loosen sooner that a bolt with no washer.
The load is in the direction of the tension in the bolt. There is relatively little transverse load or vibration.
...
It doesn't matter which end you put it on; if it is a split ring lock washer it will loosen in short order.
If it really did work you should have one on both ends, but actually that will cause it to fail even sooner.
...
a bad choice that is perpetuated out of ignorance and convenience, just like split ring helical lock washers.

This seems to depend on the application; split lock washers are not always worse than no washer. In addition to Junker machine tests showing this (e.g., https://www.youtube.com/watch?v=_LuskFWZQLY), consider this interesting posting that concludes that the common opinion that split ring washers are useless is itself an uninformed myth. It comes from the same thread I posted above, https://engineerdog.com/2015/01/11/10-tricks-engineers-need-to-know-about-fasteners/:

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"CMB042
NOVEMBER 15, 2017 AT 10:14 AM
I have found lots of references that seem very legitimate proclaim that the split lock washer is useless or worse. I work in aerospace and they are common, so I had a hard time believing it was still used based on tradition and the momentum of wrong information. So I did some research and found a very small section of Bickford�s Handbook discussing these parts. Bickford is an expert on fasteners and he has made his career studying them. His handbook is one of the most used ME references for fasteners. He refers to a study published in a journal where it was determined that they are beneficial when used appropriately.

"The pitfall all of the readily available resources fall into is assume the design intent behind the split lock washer was only to flatten the washer where the cut ends are on the same plane. The study indicates this was not the case. When load applied approaches the yield limit for the bolt, the washer twists or rolls. This is due to the trapezoidal cross section of the washer. The spring constant is much higher in this mode, and it effectively adds a significant length to the bolt. It is well documented that this has a beneficial effect on preventing loosening.

"The following is just conjecture on my part, I have not found anything solid to back it up. But I believe these were first produced prior to 1900. I could not find anybody credited with the invention. They were cheap to manufacture, and were copied and used without really understanding how they worked. I think the helical shape of the lockwasher is a result of the method of manufacture, not a requirement of the design. This was further complicated by the metric DIN standards omitting the trapezoidal shape in DIN 127. Note that ASME, MS, and NAS standards keep the trapezoidal cross-section. Studies were performed like some of the ones you cite that show they are ineffective long after the design intent was forgotten. A theoretical analysis where one does not go past the force required to flatten the washer make it appear insignificant.

"The study discussed by Bickford implies that to get the benefit from the lockwasher you must reach a certain pre-load. So the base material has to be able to withstand that load. Also the most benefit would be seen with designs where a critical joint does not have the space for a long shank bolt or screw. So they are not the best and for every application. But they are not useless either."

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Moto