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Bolt material selection

"and he's a "character" a cranky opinionated guy... much like some here..."

+1, those are great reads. Also, everyone on this forum *loves* the cranky opinionated guy - until they're on the receiving end of the 'yer fulla shit' cranky comment!
 
As has been pointed out this forum is not the place for critical bolt design, but is just fine for the OP's application.

Nevertheless I thought I'd chime in with something about corrosion.

Regarding rolled threads and corrosion resistance, I always thought rolled equals better, but the jury is still out. I am in no way an expert, but I have a customer that is. Safety critical parts. They allow no rolled threads due to the possibility of Hydrogen Stress Cracking.
Usually H stress cracking is a function of the alloy hardness, not process per se. "Grade 8" steels are chosen to have final hardness under the limit that HSC is a risk, or if needed baking can be done to drive out excess hydrogen after plating or other initiating events.
 
Usually H stress cracking is a function of the alloy hardness, not process per se. "Grade 8" steels are chosen to have final hardness under the limit that HSC is a risk, or if needed baking can be done to drive out excess hydrogen after plating or other initiating events.
Like I said I'm not an expert. One of the customer engineers is in a some corrosion society, don't know the name, and this is an area of ongoing concern and study. Enough the customer will not allow rolled threads. Apparently some concern about microhardness of rolled threads but damn hard to study.
 
I made a product for over a decade that used real long M14x1.5 12.9 socket heads. For years I had them made custom with cut threads, before eventually finding an Italian source to have the bolts made economically with rolled threads. Kind of a critical, tough application. Small bolt circle, lots of torque, vibration and opportunity for fatigue failure. Not a single bolt has ever failed. Cut or rolled. I went to rolled because they look a lot prettier.

I wonder if the corrosion failures with rolled threads have to do with how the material can kind of fold back in on itself to form the peaks of the threads?
 
As has been pointed out this forum is not the place for critical bolt design, but is just fine for the OP's application.

Nevertheless I thought I'd chime in with something about corrosion.

Regarding rolled threads and corrosion resistance, I always thought rolled equals better, but the jury is still out. I am in no way an expert, but I have a customer that is. Safety critical parts. They allow no rolled threads due to the possiblity of Hydrogen Stress Cracking. I believe studies are ongoing but apparently this is a concern due not only to internal hydrogen embrittlement but also enviormental hydrogen embrittlement.
totally depends on the metal and alloy, the corrosive environment and the heat history of the fastener, and the type of loading. so I'd say yes, the jury is out., on a pink duck on a blue moon... anything else, and no, it's settled.
(sorry, maybe a little harsh there, LOL! :D )
 
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I wonder if the corrosion failures with rolled threads have to do with how the material can kind of fold back in on itself to form the peaks of the threads?
My barely-informed take would be that the extra strain hardening of the rolling process "might" take some steel alloys into the H stress cracking range. But I agree that the little crevices you might find on some badly rolled bolts could harbor contaminants that might promote corrosion.
 
I made a product for over a decade that used real long M14x1.5 12.9 socket heads. For years I had them made custom with cut threads, before eventually finding an Italian source to have the bolts made economically with rolled threads. Kind of a critical, tough application. Small bolt circle, lots of torque, vibration and opportunity for fatigue failure. Not a single bolt has ever failed. Cut or rolled. I went to rolled because they look a lot prettier.

I wonder if the corrosion failures with rolled threads have to do with how the material can kind of fold back in on itself to form the peaks of the threads?
My very, very limited understanding points to the thread root.
 
As a student of multiple failures in Chinese Gr8 bolts,I have come to the conclusion Chinese Gr8 are the same material as Gr5 ,just hardened right out.
More like Chinese grade 8 bolts are really grade 0. A few years ago I bought a China made log splitter that was rated at 60 tons. Well the sticker on it said 60 tons but I think it is really only about 40 tons. Anyways on the first days use the "grade 8 bolts" bolts holding together all the parts that moved kept coming loose. I retightened them multiple times and an hour later they were all loose from stretching. By the end of the day some of the bolts had snapped off. McMaster sent me some Taiwan made ones and they are are still tight years later.
 
"A lot of machinists don't need to know what that is."

Yeah, who cares how strong the part you made is. Just make it out of some super strong unobtainium and it will work just fine. Until the spare tire falls off and goes through somebody's windshield. Or until the axle snaps....
The bolt doesn't keep the wheel on the carrier, just keeps the carrier hinged up into stowed position. If it failed it would just hinge down but still be attached to the truck.
 
"a lot of machinists absolutely refuse to believe this"

A lot of machinists don't know what an Instron is.
My guess is a fair number of engineers, including me, don't know what an instron is. I do now because I looked it up.:D

A fair number of machinists have at least heard of a tensile testing machine and some of the other testing machines, even if they are not familiar with the instron brand of testing machines.

Also true a lot of machinists aren't a good source for material selection. At least some of this discussion becomes moot for this application.

But it is interesting nonetheless.
 
If it is under the truck wouldn’t stainless be the nicer choice for the lucky one that has to change a tire in the sleet? Not as strong but application is also about the customer (tire changer) experience.
 
I have a couple of custom bolts to make. What's your favorite steel to use to approximate a grade 8 bolt and heat treatment? (150,000 psi tensile strength)
Not a super critical application....anything grade 5 and above would probably be adequate.
Like Milland said Fatigue Proof is your mat. No ht needed.
I made several thousand shoulder bolts for a few crane and man lift manufacturers from it. We cut mainly 1”-8 with Geometric die heads. Single point is fine.
 
The "bolts" I'm working on are for a restoration project on a GMC 2 1/2 ton 6x6 truck. The bolts are double ended studs that retain the spare tire carrier in the stowed position. By double-ended I mean it's a 3/4" stud that has a 1" hex in the center. One end bolts through the frame and the other has a large nut that retains the carrier in the stowed position. Like I said, not a super critical part. At first glance the ETD150 material looks like it might work fine. Thanks for the replies.

You use the wrong bolt for that and the truck will burst into flames and put your eyes out. Both of ‘em.
 








 
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