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Nord Locks?

Doug Rohrer

Well Known Member
I used Nord Lock lock washers on various bolted connections after seeing them coming standard on the brakes that came with my -9A kit. I am coming up on my annual Condition Inspection and am considering using Nord Locks on my six Catto prop bolts. Is anyone else doing this? Any issues?
 
Well I didn't even stay in a Holiday Inn Express last night, but I can say that my Sensenich composite GA prop came with nord lock washers as standard for all of the bolts. The design of the hub kind of mandates it (safety wire wouldn't work very well). I admit to being a bit sketched out at first, but they seem to work well.
 
I used Nord Lock lock washers on various bolted connections after seeing them coming standard on the brakes that came with my -9A kit. I am coming up on my annual Condition Inspection and am considering using Nord Locks on my six Catto prop bolts. Is anyone else doing this? Any issues?

Since the prop has to be retorqued twice a year, Nord lock washers might have to be changed out every two years. I'd call Catto...

I think they are recommending Bellville washers (at least for pushers) to apply a more consistent load to the crush plate (with respect to temperature/humidity changes).
 
Since the prop has to be retorqued twice a year, Nord lock washers might have to be changed out every two years. I'd call Catto...

I think they are recommending Bellville washers (at least for pushers) to apply a more consistent load to the crush plate (with respect to temperature/humidity changes).

Here is what Nord-Lock has to say about the reuse of their washers.

I will not comment on other type washers.
 
I used Nord Lock lock washers on various bolted connections after seeing them coming standard on the brakes that came with my -9A kit. I am coming up on my annual Condition Inspection and am considering using Nord Locks on my six Catto prop bolts. Is anyone else doing this? Any issues?

No issue at all. They are slightly thicker than a standard AN960 washer and you should account for that in bolt length, but they work great and are used by Whirlwind as well.

As for the follow-on topic of reuse, I find that I get about 3 good torque events with them. After that, the break-away torque starts to drop off as the teeth start to round.
 
No issue at all. They are slightly thicker than a standard AN960 washer and you should account for that in bolt length, but they work great and are used by Whirlwind as well. .

Not on all the Whirlwind props. I hate safety wiring my 200RV prop so checked with WW about using Nordlocks instead. They did not recommend them. Not sure of the reasoning.
 
Nord Lock Torque Values

Nord Lock website has their own torque values.

While they don't have a category for our AN bolts they do have some of the other standards.

Looking at a Grade 5 1/4-20 with a friction value of around .15 'lubricated' I compare Nord Lock values with engineering@fastenal values.

Nord Lock: 8.8 ft-lbs with a clamp value of 2235 lbs
Fastenal: 6.33 ft-lbs with a clamp value of 2029 lbs

Close but not the same, anyone know whether our torque values need to be adjusted using Nord Locks?
 
Nordlock washers are great, I had a problem with a 1,000hp engine alternator pully spinning to 7k rpm and launching at a track. The alternator pulley would end up loosening and spinning off the snout after awhile with conventional loctite and alternator nut. After using the nordlock washer, I have never had a problem since. The environment I used them in is a high vibration, high g environment from the nut's prospective.

Also, my Sensenich 3 blade composite prop has them.
 
Nord Lock website has their own torque values.

While they don't have a category for our AN bolts they do have some of the other standards.

Looking at a Grade 5 1/4-20 with a friction value of around .15 'lubricated' I compare Nord Lock values with engineering@fastenal values.

Nord Lock: 8.8 ft-lbs with a clamp value of 2235 lbs
Fastenal: 6.33 ft-lbs with a clamp value of 2029 lbs

Close but not the same, anyone know whether our torque values need to be adjusted using Nord Locks?

Typically from a mechanical perspective the bolt torque is dependant on the threads, bolt thickness, and if it is a dry or lubricated torque application. The washers should not affect that value.
 
Thanks to all who responded. It seems that Nord Locks can be safely used on prop bolts. I will confirm with Catto. Since I will only be checking torque and not removing them periodically, the ramps should not get worn down. Not true for the caliper bolts. I have a stash of various sizes as they are remarkably inexpensive from ACS.
 
Typically from a mechanical perspective the bolt torque is dependant on the threads, bolt thickness, and if it is a dry or lubricated torque application. The washers should not affect that value.

That begs the question why Nord Lock would create their own torque values that are different from values based on the bolt. Perhaps the harder the bolt the more stress is required to achieve the locking property. Maybe it's that when friction goes up torque must increase to achieve the desired bolt tension (like using a nyloc nut), perhaps the serrations are creating additional friction? Worth knowing why Nord specifies unique torques if we use their product.
 
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That begs the question why Nord Lock would create their own torque values that are different from values based on the bolt. Perhaps the harder the bolt the more stress is required to achieve the locking property. Maybe it's that when friction goes up torque must increase to achieve the desired bolt tension (like using a nyloc nut), perhaps the serrations are creating additional friction? Worth knowing why Nord specifies unique torques if we use their product.

https://www.nord-lock.com/insights/...i-change-my-tightening-torque-with-nord-lock/

Here is the answer. They even state that using standard torque values will reduce preload by about 10% to 20% which for our applications really wouldn't matter. Their numbers are based on their own testing with under bolt clamping force measurements.
 
Well Done!

https://www.nord-lock.com/insights/...i-change-my-tightening-torque-with-nord-lock/

Here is the answer. They even state that using standard torque values will reduce preload by about 10% to 20% which for our applications really wouldn't matter. Their numbers are based on their own testing with under bolt clamping force measurements.

So it is additional friction like our friction nuts. As we strive to do things as accurately as we can (we do add the additional torque required for friction nuts right?) we need to add additional torque for friction washers in order to achieve design bolt tension! I'll chuck that over to Safety.
 
No Friction

Hmmmm... I don't see why the torque value would change while tightening the bolt. The Nord Lock just acts like two thin washers under the bolt head during tightening. We do not adjust torque settings when we add a second flat washer under a nut, so why would we treat Nord Locks differently? Of course the removal torque is much higher: that is how they work.
 
Hmmmm... I don't see why the torque value would change while tightening the bolt. The Nord Lock just acts like two thin washers under the bolt head during tightening. We do not adjust torque settings when we add a second flat washer under a nut, so why would we treat Nord Locks differently? Of course the removal torque is much higher: that is how they work.

According to Nord Lock it is the other way around. Extra friction caused by locked cams and serrations on the tightening. Untightening feels easier as the system unloads after cams release. Depending on whether lubrication remains on cams (recommended), even the initial unlock may feel like less torque. Check out their link provided in previous post:

"Nord-Lock’s general tightening guidelines are taking the increased friction into account"

If Nord Locks didn't have any additional friction, then they would act as a plain washer once cam-ed together right? They call them 'tension lockers,' but they really need that additional friction too.
 
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Not on all the Whirlwind props. I hate safety wiring my 200RV prop so checked with WW about using Nordlocks instead. They did not recommend them. Not sure of the reasoning.

They use them on all of the ground adjustable and fixed pitch props. For constant speed, different animal, yes, those are safety wired. It doesn't mean you can't use the Nordlocks, but you should still safety wire your drilled bolts.
 
OK, I think I see the issue now. The "outer" sides of the two halves of the NL washers have small radial serrations to prevent the bolt from rotating without dragging the washer half with it. Torquing the bolts has to overcome the added friction of the serrations. However, the torque required to loosen the tightened bolt is significantly higher than the tightening torque, until the cams release.
 
Interesting discussion. I never heard of the Nord-Lock before. I may use them on my alt and a/c bracket mounts at my next condition inspection. My Hartzell constant speed prop uses safety wired bolts. I noticed on the Junkers Test video on the Nord-Lock site that there is an initial settlement as the washer teeth dig into the nut and material. So if you want the desired final bolt load, a little additional torque would be required.
 
I used Nord Locks as supplied with the brake calipers, the alternator bracket bolts, the gascolator bowl bolts and the carb attach studs. You need to mark each location in a permanent manner so anyone looking will not assume you forgot to safety wire it.
 
I just installed them on my new GA whirlwind prop. Very cool.

I got a supply of various sizes for future maintenance. Definitely going on the gascolator. Nordlocks would of been nice to have when I replaced my fuel pump. The safety wire in tight place is PITA.
 
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