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  #1  
Old 06-13-2021, 08:34 PM
WayneJ WayneJ is offline
 
Join Date: Mar 2012
Location: Auburn, Washington
Posts: 30
Default My nuts are galled, 25-05 step 8


I installed the AN3-13A bolts then realized I chose the wrong Cover Rib so removed the bolts and found badly galled threads. We all know these all metal locknuts work like platenuts (nutplates?) and are deformed to apply an interference fit as the locking mechanism. But is it normal to get this kind of galling? The photos show the relative location of the nut when installed. The bottom of the nut is not deformed and does not cause galling. Nylock nuts are re-usable but I have not read that all metal locknuts and the bolts they are installed on are one time use only. I will not reuse these. I this normal?
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  #2  
Old 06-14-2021, 05:32 AM
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RV6_flyer RV6_flyer is offline
 
Join Date: Jan 2005
Location: NC25
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Default

Quote:
Originally Posted by WayneJ View Post

I installed the AN3-13A bolts then realized I chose the wrong Cover Rib so removed the bolts and found badly galled threads. We all know these all metal locknuts work like platenuts (nutplates?) and are deformed to apply an interference fit as the locking mechanism. But is it normal to get this kind of galling? The photos show the relative location of the nut when installed. The bottom of the nut is not deformed and does not cause galling. Nylock nuts are re-usable but I have not read that all metal locknuts and the bolts they are installed on are one time use only. I will not reuse these. I this normal?
That is NOT normal.

Not sure where your info comes about metal locknuts not being reusable but it is false. Metal locknuts, just like nylocks, are reusable if they still provide resistance.

Been using metal locknuts like in your photo for over 20-years and have never seen one like that. Looks over torqued or maybe I should say it looks like an over tighten fastener.
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  #3  
Old 06-14-2021, 05:45 AM
terrykohler terrykohler is offline
 
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Default Hard to tell by looking at the Pictures

Best if you look at these using a magnifying glass. It's not unusual for all-metal lock nuts to strip a little plating. You'll be able to tell pretty easily if it's just a little plating or it's really galling with some magnification. Look at the thread form.
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  #4  
Old 06-14-2021, 09:22 AM
Norman CYYJ Norman CYYJ is offline
 
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Default

Looks like the wrong thread on the nuts.
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  #5  
Old 06-14-2021, 09:29 AM
PhatRV PhatRV is offline
 
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I had to throw out a couple of metal nutplates that had damaged the bolt threads like in your picture. Most of the AN parts have tight tolerances but they aren't perfect. Find and new metal nut and test it with another new bolt. You should be able to screw on / off a few times before the threads give out.
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  #6  
Old 06-14-2021, 12:47 PM
Norman CYYJ Norman CYYJ is offline
 
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Instead of using a new bolt use the old bolt and thread the nut on further. If it is still a problem you haven't wasted another bolt.
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  #7  
Old 06-14-2021, 02:28 PM
Scott Hersha Scott Hersha is offline
 
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I agree with Terry. I think you are seeing CAD plating removal because of the tight fit of the lock nut. The nut is CAD plated too, so the initial fit gets very tight, loosens up a bit when the plating is scraped off, but still performs as a lock nut.
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  #8  
Old 06-14-2021, 03:16 PM
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If you can turn the nut by hand it's time to replace it.
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  #9  
Old 06-14-2021, 05:24 PM
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Walt Walt is offline
 
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Quote:
Originally Posted by Norman CYYJ View Post
Looks like the wrong thread on the nuts.
Agree, looks like coarse thread bolt with MS fine thread nut, stripped.
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  #10  
Old 06-14-2021, 07:32 PM
WayneJ WayneJ is offline
 
Join Date: Mar 2012
Location: Auburn, Washington
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Default I could be overthinking this.

The thread size is verified 10-32 on both parts. Not the wrong size or pitch.

Looked at the threads under magnification and can see what looks like galling. Blobs of metal in the threads. It doesn't show up well in the photos.

Ran the nut on and off both bolts about 6 times each. They went on and off just fine, got looser though. The prevailing torque started at about 8-10 in lb and is now about 5 in lb.

I used a scribe and a brush to clean out the threads. Lots of fine particles. This could be plating particles but the color looks like steel. Maybe both.

Bottom line, after playing with this today I think it's a non issue. The assembly seems to be sound in spite of the way it looks.

Just for fun I put one of the (2) bolts that I've been playing with into the assembly and over-torqued it. Went up 10 in lb at a time and it held to 100 in lb. At 110 in lb the threads started to strip and the wrench would not click.

My final torque calculation is 28 + 8 = 36 in lb. Per the chart on KAI page 05-20 and measured prevailing torque of 8 in lb.

Maybe someone out there could try this to see if you get the same result. AN3 bolt and MS21042-3 nut.
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