What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

My nuts are galled, 25-05 step 8

WayneJ

Member
:(
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?
 

Attachments

  • IMG_7172.jpg
    IMG_7172.jpg
    386 KB · Views: 505
  • IMG_7173.jpg
    IMG_7173.jpg
    531.1 KB · Views: 334
:(
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.
 
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.
Terry, CFI
RV9A N323TP
 
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.
 
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.
 
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.
 
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.
 

Attachments

  • IMG_7178.jpg
    IMG_7178.jpg
    395.2 KB · Views: 247
I've used quite a few of these and have never seen that - is it possible you got a bad batch? The corners on the nut look like the plating is flaking off - not normal.
 
Poor quality nuts?

Looks like the wrong thread on the nuts.

Agree, looks like coarse thread bolt with MS fine thread nut, stripped.

The threads looked off and this was my first thought too, but based on AN3 diameter of .189 then scaling that against the threads 32 pitch should yield 6 threads for the that diameter and it does. 24 TPI would have been 4.5 threads.

May just be poor quality nuts. Over a decade of looking at surplus/new hardware at the OSH flea market, quite a bit of difference has been found. And it is not always related to the price.
 
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.

Don't know about Y'all, but I can't read the title of the thread without chuckling:).... Anyway, if you've confirmed the pitch of both parts, I would purchase new of all the hardware and verify everything again. You may have gotten hold of hardware that was not properly heat treated/hardened. It's a peace of mind thing.
 
If it were me, I would replace them. It looks to me like the nuts were run down fast with a powered driver maybe, and maybe a couple of times very close together in time. That can create a lot of heat and cause damage up to and including galling. In any case, I wouldn't worry about it beyond replacing the fasteners. Takes time to order and receive, but that's what I would do. they could completely gall the next time you remove them from the looks of them and if you think you are frustrated now, just wait until then...

That said, if they have sufficient lock (torque), they will likely be fine structurally.

Tim
 
“My nuts are galled”

C’mon Man, 14 posts and only Larry picks up on a hilarious title? Sure glad mine aren't galled, that would hurt. Yes I’m a sicko
 
Back
Top