Failed heim stud

[bfluegel]

I used this tapered Heim stud at the pitman arm ten years ago and haven't removed it until now. I was working nearby, inadvertently bumped the nut shown, and it just fell to the floor. Could this have been caused by over torquing? The stud was still solid in the tapered hole of the pitman arm and I had to use a TRE puller to remove it.
Thanks.

 

[661buster1963]

I am no metallurgist, but always believed a flat fracture like that to be from a tensile failure. Since the taper was tight and carrying the load first thing to come to mind would be an over torqued situation. Would be a little unsettling if it ever happened again, you are lucky. Go buy power all ticket.

 

[DirtDonk]

And this is why properly sized, clean and tight tapered mating joints are so important!

 

[DirtDonk]

I always worry about those necked down sections between the threads in the shanks. I guess in this case that wasn’t the weak link after all.
Interesting design at the other end though. What width two diameter threads involved.
What’s that all about?

 

[bfluegel]

I always worry about those necked down sections between the threads in the shanks. I guess in this case that wasn’t the weak link after all.
Interesting design at the other end though. What width two diameter threads involved.
What’s that all about?

I wondered about the necked down section, too.
The change in thread diameter is just an illusion of the photograph. The wrench flats and the pin hole make it look smaller, but it is all 9/16".
It's possible that I over torqued this ten years ago by looking at a table for unplated bolts and also from moving to the next slot in the nut. But I can't understand how it could survive the tightening process and then break at a later time. I know I used a torque wrench and then probably a breaker bar to get to the next slot. No impact wrench.
I used the same studs and procedure at the knuckles, so it is definitely unsettling.

 

[73azbronco]

so the top part in the nut is long term fatigue, bottom part is just the point it all failed. When? You got one strong bump going for you.,