Re-torquing bolts. Do you replace or re-use old bolts?

[dixiemountaineer]

I've always been told not to re-torque bolts if it can be avoided and its better to replace them in certain applications, for example automotive applications where integrity of the fasteners are critical. The reason being is that torqued bolts somewhat stretch and threads purposely deform during the tightening process. I thought about this after I installed my WDH and wondered about loosening them for adjustments at any time in the future, then having to re-torque them. Anyone have thoughts about this?

 

[Kevin D Pem]

Well I have a story. I rebuilt an engine back in the late 80's I had done it for years. I didn't replace the rod bolts and had a rod shoot out of the side of the block withing 1000 miles. When I took it apart I found a cracked rod bolt was the problem.

I have not reused any bolt after that problem. I have never had such a failure sense that failure. I would say find a bolt house.

 

[TJ&LadyDi]

My long-time practice is to use new bolts in any application where a torque specification is provided. Additionally, in any application that I feel is critical for safety, I replace old bolts with new even if there is no torque specification. I will re-use old bolts in non-critical applications if they are not rusted or deformed.

Those lessons were learned years ago in the course of building and maintaining high-performance cars; street and racing. You don't want things coming apart when you are in a potentially dangerous situation.

TJ

 

[BGMAC]

This talks about causes of bolt failures. FYI; under torquing can cause failure as well.
During my time in the Air Force as a jet engine mechanic, some torquing requirements has us measure the bolts after torquing to determine how far the stretched.
Another unique thing, we had a hydraulic torque wrench that weighed in at 150 lbs. We would torque the turbine nut to 180,000 psi. To get it off after the engine was used took 300,000 psi. We had to use anti seize compound with embedded silver costing $1000 a pint.

https://www.bakerrisk.com/wp-content/uploads/2015/03/avoiding-bolt-failures.pdf

 

[Joe Hogan]

Interesting article on this topic Reuse of Fasteners | Fastenal

or https://www.boltscience.com/pages/the-re-use-of-threaded-fasteners.pdf

 

[Gronk]

So, what do you guys do with wheel studs?

 

[Kevin D Pem]

So, what do you guys do with wheel studs?

I tork them and wait for them to fail. Although the torque used on them is not quite as high as the bolt will deform. Remember the days when impact wrench was used at the tire shop? Not any more.

 

[Joe Hogan]

So, what do you guys do with wheel studs?

Since it is common practice to reuse the studs, and even the nuts, I guess they are way over built. That said, I have had wheel studs fail more than a few times back in the 60s, 70s, and 80s when I was putting lots of miles on vehicles.
Looking back on those times it was probably a combination of poor OEM quality of fasteners and over torque with impact guns. But the stud would shear off typically on the road and bang around in the hub cap until I notice it and replaced it.

 

[Kevin D Pem]

I was in the forest this summer and destroyed one of my solar panels while parking in a very rough location. The bouncing broke or disconnected a trace in the panel so I needed to replace the panel. I had to completely modify my mounting system and to do that I had to unbolt many parts. To keep rust down I use stainless bolts. Stainless in any configuration has more problem than steel with stress cracking. I typically buy my bolts 100 at a time, The rest of the bolts I don't use go into my junk drawer. I knew I had bolts so I started my project. A couple of the bolts broke when taking apart the old and I had to use my angle grinder to remove a few that galled. No problem I said I wasn't going to use them anyway.

I was a couple bolts short and decided to see if I could get away with using a couple of old ones. I marked the locations that I would replace those bolts when back in the real world and went to work. A little more than half the bolts seized and the only way to get them back out was with the angle grinder. I did get the job done but worried all the way to town that the new panels would find their way into the way of other drivers behind me.

Nothing is more undesirable than a junk drawer full of used junk bolts. Nothing but new make it into my drawer for a reason.