Flattened threads in part of hole

[explorer2030]

What would cause internal threads to look flattened on one side of a hole, and normal in the rest of the hole like the images below? These threads are part of a turnbuckle on a differential case spreader that required much more force than I expected to tighten it under load the first time I used it, and the threads started creaking when I loosened it even though I applied moly grease beforehand. I would like to know if this could be a manufacturing defect, or more likely caused by me overtightening it. I noticed no metal shavings upon disassembly to indicate thread stripping, and the male threads of the turnbuckle look normal.

 

[Dave9]

Without watching you use a torque wrench, how would we know if you over-tightened it?

I'd guess that otherwise, it just wasn't tapped well... maybe a dull tap bit?

 

[paulo57509]

There is a thread form called, Sellers' Thread; 60* with flat crest and root. I don't know if this is what you have. I've never seen this thread form and I wouldn't know where it's used.

Could it be some kind of upset thread locking mechanism?

 

[Dinoburner]

From the pics the hole looks over drilled that is too large a drill was used.

 

[explorer2030]

From the pics the hole looks over drilled that is too large a drill was used.

Would this cause the threads to bind up under load?

 

[Exhaustgases]

Pictures are pictures need to see in person. But first thing comes to mind is the threads are not centered in the hole.
How can that happen? If they are threaded on a lathe and the hole is not centered then that happens.
Or if a thread mill was used and the hole was not centered or in either case the part moved, then the threads come out like that.

 

[Dinoburner]

Would this cause the threads to bind up under load?

Yes, sort of like a wavelok bolt.