Lock N Roll bolt thread failure

[teotwaki]

When I bought my trailer the original owner and I were going to transfer the Lock N Roll coupler to my receiver hardware but the main big nut seemed stuck. We left it as it was and when I got home I soaked the threads in various penetrents but still had trouble. I called Lock N Roll and got a cranky guy who said absolutely no warranty on the bolt so I had to order a new piece.

Once the new piece came in I decided to see how things looked.

On the new one you can see a change in color on the threads part way up from the end.


I tried the new nut on the threads and when it was about this far up....


... it felt "funny", almost gritty. I ran a tap in the nut and a die on the threads and tried again and it still felt funny.

On the original coupler you can see that the exposed threads look OK.


So I went ahead and forced the nut off of the "old" coupler and...OUCH


Well, have to keep going and ruin the threads all the way out.


On the new coupler I coated the bolt quite liberally with an anti-sieze grease before using it.

So I'm thinking that Lock N Roll has a manufacturing problem. (?) The factory thread job appears to be a stamped set of threads rather than a machined set. There was not enough metal for a die to really reshape the threads.

Has anyone ever seen something like this? Is this a common failure?

 

[Borrego60]

Thats really a bummer,looks like maybe the nut was not seated or something. The nut should had came off cleanly. Have you looked at the Max coupler yet? now rated class lll. I would agree it looks like it was a stamped thread instead of machined. Color change is odd too.

 

[JIMBO]

:sombrero: Thats too bad about the Lock&Roll, but it's standard procedure in the auto/aircraft business

The threads (bolt/nut), are made to different specs (MINOR) so that the nuts won't just back off--think spring U bolts and jeep lower control arms, but

You may be right about the Lock&Roll, I hope I don't have to make any changes to mine

Thanx for the info !!

:costumed-smiley-007:wings: JIMBO

 

[R_Lefebvre]

Ok, first of all, rolled threads are stronger than machine cut threads. By running your die on the bolt, you've just destroyed it. Sorry. I would seriously throw it away. Whatever Grade it was, has just be lost. Cut threads have sharp roots, which increases the chance of cracking. Rolled threads are almost like a forging, in that you get a beneficial grain orientation around the roots.

As for the coating discoloration and gritty feeling, I'm guessing it's just something with the plating process. That looks like a large bolt, it's probably not surprising.

I'm not sure why the original thread stripped out like that, but it might have been overtightened. The threads started to strip, but didn't fully. Then when you tried to back it off, the threads of the stretched portion don't line up with the non-stretched, and that's what happens.

Yep, that's my best guess about that.

Is it supposed to be torque-to-yield?

 

[Martyn]

Over the years we sold a lot of Lock-n-Roll couplers, I never saw this problem with any of them. As Rob said the discoloration seems to be a plating issue.

Great Lakes Forge who make the Lock-N-Roll are a full on forge, and they make heavy duty military equipment, think tank gun turrets etc. From a manufacturing view point I think they are a very sound company.

Due to the way that the vehicle end of the coupler is made the only solution is to buy a new one.

 

[teotwaki]

Ok, first of all, rolled threads are stronger than machine cut threads. By running your die on the bolt, you've just destroyed it. Sorry. I would seriously throw it away. Whatever Grade it was, has just be lost. Cut threads have sharp roots, which increases the chance of cracking. Rolled threads are almost like a forging, in that you get a beneficial grain orientation around the roots.

As for the coating discoloration and gritty feeling, I'm guessing it's just something with the plating process. That looks like a large bolt, it's probably not surprising.

I'm not sure why the original thread stripped out like that, but it might have been overtightened. The threads started to strip, but didn't fully. Then when you tried to back it off, the threads of the stretched portion don't line up with the non-stretched, and that's what happens.

Yep, that's my best guess about that.

Is it supposed to be torque-to-yield?

Let me start by saying thanks for the response! I feel that there is more to information to be shared before I would throw away the new coupler.

The die just spun on and off and did not cut anything, as if there was not enough metal to even cut. I can't believe that there is any reason to throw away the part.

It is entirely possible that the first failure was over-tightening. Essentially it was a used coupler of unknown origin that came with the trailer and now the problem is mine. :ylsmoke:

 

[MotoDave]

It looks to me like the nut might not have been torqued properly (or the torque spec is inadequate), allowing the parts to shift and contact the threads of the bolt. The threaded portion of the bolt becomes a bearing surface, and gets destroyed. Bolts are not meant to be pivots, the torque should be designed so that the tension in the bolt holds the mating parts together. If a bolt has to be used as a pivot, the pivoting portion MUST be on the unthreaded shoulder of the bolt, not the threaded portion.

 

[R_Lefebvre]

If the die seriously didn't cut any metal, then OK. But that would likely mean the original thread was a bit undersized.

BTW, on the plating... what you felt isn't really surprising. About 5 years ago, the industrialized countries banned hexavalent chromium as used in cad plating. This led to the development of hex-free cad plating for bolts. It ended up being a significant issue, I went through it when I was at Ford. IIRC, we had to reengineer many bolted joints because the new plating was in fact "stickier".

 

[teotwaki]

Over the years we sold a lot of Lock-n-Roll couplers, I never saw this problem with any of them. As Rob said the discoloration seems to be a plating issue.

Great Lakes Forge who make the Lock-N-Roll are a full on forge, and they make heavy duty military equipment, think tank gun turrets etc. From a manufacturing view point I think they are a very sound company.

Due to the way that the vehicle end of the coupler is made the only solution is to buy a new one.

I also wanted to thank you for adding in your considerable knowledge for the benefit of someone who doesn't own an AT trailer :sombrero:

I did buy a new one after the cranky guy at Lok N Roll wouldn't even discuss the issue. It was "order a new part or I'm hangin' up" without any interest in the failure of the first part. I would have shipped the bad one to him on my own dime just to find out if it was abuse and not a failure.

What made my sentiments towards them a little worse is that I ordered one from them and it did not show up on time. When I called to inquire he admitted that he had mis-spelled my street name, made one attemtp to call me (misdialled) and got some strange recording. Then after two days he suddenly "remembered" how to spell the street name and shipped the part out late. A very "take-it-or-leave-it" attitude the whole time. Since I only had half of a hitch he must of felt I was a captive customer and I had to give him my money.

 

[ddog45]

Mine looked exactly the same when I had to change hitches after buying a landcruiser. I think it is a design problem. For the cost of these things I dont really feel they should be a one time use sort of part. We have two vehicles that we like to pull the chaser with now and then and sadly they have bumper hights so I have had to change my lock and roll a few times at this point the threads look wasted. Needless for me to say the hitch works great but I am not impressed with the thread quality. Oh I will just spend another 250 like everyone else and shut my mouth. Thats a joke Im looking for another product to use that I can get my moneys worth out of. If someone is unhappy with my statements they can send me a new hitch.

 

[Martyn]

I also wanted to thank you for adding in your considerable knowledge for the benefit of someone who doesn't own an AT trailer :sombrero:

I did buy a new one after the cranky guy at Lok N Roll wouldn't even discuss the issue. It was "order a new part or I'm hangin' up" without any interest in the failure of the first part. I would have shipped the bad one to him on my own dime just to find out if it was abuse and not a failure.

What made my sentiments towards them a little worse is that I ordered one from them and it did not show up on time. When I called to inquire he admitted that he had mis-spelled my street name, made one attemtp to call me (misdialled) and got some strange recording. Then after two days he suddenly "remembered" how to spell the street name and shipped the part out late. A very "take-it-or-leave-it" attitude the whole time. Since I only had half of a hitch he must of felt I was a captive customer and I had to give him my money.

There are a number of companies out there who make good products but have lousy customer service. It would be best if they stayed in manufacturing and left the sales to others, but the profit margin from direct sales is much too enticing.

 

[Martyn]

Mine looked exactly the same when I had to change hitches after buying a landcruiser. I think it is a design problem. For the cost of these things I dont really feel they should be a one time use sort of part. We have two vehicles that we like to pull the chaser with now and then and sadly they have bumper hights so I have had to change my lock and roll a few times at this point the threads look wasted. Needless for me to say the hitch works great but I am not impressed with the thread quality. Oh I will just spend another 250 like everyone else and shut my mouth. Thats a joke Im looking for another product to use that I can get my moneys worth out of. If someone is unhappy with my statements they can send me a new hitch.

Your identical issue is now the second occurrence that I have heard about, the first being the original post.

I don't think you should throw another $250.00 at the problem. I'd suggest a call to the manufacturer to see if they can address the problem. Two brothers own the company, hopefully you won't talk to "Grumpy".

If you have no luck I'd be happy to supply you with a Max Coupler

 

[teotwaki]

Your identical issue is now the second occurrence that I have heard about, the first being the original post.

I don't think you should throw another $250.00 at the problem. I'd suggest a call to the manufacturer to see if they can address the problem. Two brothers own the company, hopefully you won't talk to "Grumpy".

If you have no luck I'd be happy to supply you with a Max Coupler

Believe me, a Max Coupler was the first thing I considered but although a more expensive solution it would have been the end of the whole matter. :sombrero:

Now that I own a trailer you have a lot of products that are on my radar screen: fuel can holders, tire rack, etc. I daresay I'll send some business your way sooner or later!

 

[Martyn]

Believe me, a Max Coupler was the first thing I considered but although a more expensive solution it would have been the end of the whole matter. :sombrero:

Now that I own a trailer you have a lot of products that are on my radar screen: fuel can holders, tire rack, etc. I daresay I'll send some business your way sooner or later!

Just send me your credit card details and I'll get you on our monthly installment plan :elkgrin:

 

[teotwaki]

Just send me your credit card details and I'll get you on our monthly installment plan :elkgrin:

Maybe I should just have my employer enroll me in your "AT Direct Deposit Plan"?? If any money is left over you can mail me a check..... :hehe::

The person at Lock N Roll who responded via email was Gregory Russell. Don't know if he is one of The Brothers. I just emailed him the photos and told him I am not the only one who has a problem with the bolt failure.