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  #1  
Old 10-31-2018, 11:43 PM
TASEsq TASEsq is offline
 
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Location: Melbourne, Australia
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Default MS21042 nut running torque

Just thought I would share my findings with others to make sure everyone else uses about the same running torque?

Please let me know if you are the same / significantly different!!

Setup was an AN3 or AN4 bolt held in a drill press vice which was clamped to the table so it couldn?t rotate. I then ran the nut onto the bolt so that about 1 thread was showing out the end (so full contact with but threads by the bolt). The scale was read while the nut was in motion, and the wrench was held at the end on the black knob.

Findings were (measured running torque):
AN3 / MS21042-3: 10 in/lbs
Photo here: https://photos.app.goo.gl/7x8RaqQewQXRXBj16

AN4 / MS21042-4: 24 in/lbs
Photo here: https://photos.app.goo.gl/sNossUFGPXjkcWfw7

As such on my click type torque wrench I would use as the wrench setting:
AN3: 38 in/lbs (28 + 10)
AN4: 109 in/lbs (85 + 24)

Look forward to some concurrence / discussion!
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  #2  
Old 11-01-2018, 03:43 AM
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Steve Melton Steve Melton is online now
 
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you must allow for running torque. if I remember correctly, my numbers were less than half of what you posted for nylocs.

edit: the nuts you are testing are not nylocs.

folks should remember the bolted joints,attachment fasteners and hinges are the most critical parts in the build. even more important than rivets.

good job to do the check.
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Last edited by Steve Melton : 11-01-2018 at 03:56 AM.
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  #3  
Old 11-01-2018, 08:04 AM
HFS HFS is offline
 
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Default AN 365 Elastic Stop Nut Retention Force

I have done a lot of testing of "retention" torque for the AN365 series hex nuts and following are the results.

AN365-3 = 5.0 in-lb
-4 = 9.3 in-lb
-6 = 41.4 in-lb

What I call the "tare" torque increases the torque specs to:

-3 = 20 to 25 + 5 = 25 to 30 in-lb
-4 = 50 to 70 = 9.3 = (approx.) 60 to 70 in-lb
-6 = 160-190 + 41.4 = (approx.) 200 to 230 in-lb

In general terms, if you torque to the high end of the range (+ a "skosh"), you will probably remain inside the allowable range.

Also, regarding reusing these fasteners - the retention torque goes way down (can you say 50%) on the second application. There are specs out there on the reduction of this value, down to the 5th reuse.

Note: Testing done with a purpose made 12" moment arm wrench, a .1 gram digital scale, at least 1 full thread showing past nylon insert, and the load at stiction being discounted.

Of course, as always YMMV

HFS
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  #4  
Old 11-01-2018, 12:27 PM
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To avoid confusion when discussing details, it is always helpful to use the official nomenclature.
The measurable torque that exists while turning a fasten prior to a fastener bottoming out and beginning to tighten, because of a self locking feature, is referred to as prevailing torque. An alternative (but lesser used in aviation) nomenclature is running torque.
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  #5  
Old 11-01-2018, 10:02 PM
TASEsq TASEsq is offline
 
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I also just tested some AN365 nuts and found the following:

AN365-1032A (AN3) = 3 in/lbs
Photo here:https://photos.app.goo.gl/oFMqBrDj1jF8AgGG7

AN365-428A (AN4) = 15 in/lbs
Photo here:https://photos.app.goo.gl/oFvmVyUwNBNjc8RG8

Section 5 also had the following comment:
?As an example illustrating the importance of determining the friction drag torque consider a new AN3 bolt and MS21042-3 all-metal
lock nut. Our tests showed an average friction drag torque of 14 in-lbs (your results may vary)?

So I reckon the 10 in/lbs is good for my HS bearing brackets - 38 in/lbs total.
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  #6  
Old 11-02-2018, 09:19 AM
brian257 brian257 is offline
 
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You will find the torque to vary on different nuts from different manufacturers. I would not even be surprised to find small variations on nuts from the same manufacturer.
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  #7  
Old 11-02-2018, 12:54 PM
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Quote:
Originally Posted by brian257 View Post
You will find the torque to vary on different nuts from different manufacturers. I would not even be surprised to find small variations on nuts from the same manufacturer.
And also variations between new unused bolts and bolts that have been previously used in a self-locking fastener.
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  #8  
Old 11-02-2018, 01:28 PM
JwWright57 JwWright57 is offline
 
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Trent - i was getting the same 10 in pds using a similar beam scale.
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  #9  
Old 11-02-2018, 07:51 PM
TASEsq TASEsq is offline
 
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Awesome - thanks all.

I was thinking I could just use the same value going forward but sounds like it might just be easier to do the nut up with the beam type wrench and measure the ?prevailing torque? with each nut, then finish with the proper calibrated click type.
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  #10  
Old 11-03-2018, 11:32 PM
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There was just recently another very informative thread on this topic. I found the replies to be very helpful, and came to the same conclusion: a flex-beam style torque wrench is super useful for both measuring and torquing.
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