Making High Strength Bolts

[AllenH59]

This is just winter curiosity, but I wonder if it is possible. Aftermarket head studs for my truck engine claim to be 220k psi, and 14mm bolts take 214 ft/lbs of torque to collapse the gasket and hold down the head. I am wondering if any of you have made bolts to equal this kind of strength.. A blacksmith buddy has a marvelous propane forge.. you know what I am thinking.....

[John Evans]

Well if it is a stud and not a headed bolt ,that makes thing just slightly easier!! First you need to select the proper material ,then the correct heat treating [don't think a blacksmith with a forge is going to cut it!} Then most high strength fasteners use rolled threads not cut !

[AllenH59]

Yes John Evans, I am just curious how strong of a bolt we can make. I know that single point threads are not as strong as rolled threads, and every consideration to doing a good job would have to be attended to. I would not make head studs, as who wants to have their own cheapness have them broke down by the road... I have pulled 100 ft lbs on bolts 5/8" studs I made with no problem, and no heat treating.. Going down to 14mm and up to 214 ft lbs is a big step..

[BadDog]

I've acquired B7 threaded rod in various sizes for some of the high strength stuff I've done in the past. But don't expect to get anywhere near those high end studs, which are highly engineered with specific alloys and complex heat treat (and related) operations to achieve that result. The end result is also often designed as a single use "torque to yield". It's unlikely that any home shop hardware is going to get anywhere near that.

However, for less stratospheric goals, good functional shop made hardware is possible, though still problematic. Oxidation/scale, atmospheric control, and precise lengthy temperature controlled processes are still needed, and often requiring non-trivial finish grinding (threads and shanks) if you hope to achieve good results.

I've made a number of fasteners from already heat treated material. For my time and effort, it's generally more productive to do that, or if available commercially, just buy it and get on with things. Then again, if I were very practical in such things, I would have to acknowledge that for a very large part of what I do in my shop, there are far cheaper/easier/faster ways of getting there. But I have to justify all that tooling for the "can't be purchased" options that I come across fairly regularly.

[Harold_V]

If you're serious about making high tensile studs, you might consider exploring Vascomax. It's capable of extreme tensile strength and is a precipitation hardening material which heat treats at less than 1,000° F with little or no scaling.

It's not cheap!

H

[John Hasler]

Also note that the relationship between torque and tension can vary a lot depending on factors such as material type and thread finish and quality. You'll want to measure how much the studs actually stretch. Don't assume that torqueing yours just like the factory ones will result in the same tension.

One of the ways those studs are "highly engineered" is by optimizing the cost of the material. As Harold suggests, it might be possible to meet that spec by starting with a material that an automotive engineer would never consider.

Relevant: https://www.boltscience.com/

[Rich_Carlstedt]

Material Strength has several forms
We had a problem with 1" studs ( x 10") breaking. They held down high speed 40 Ton presses to their floor foundations
We made the studs out of 4140 and heat treated them and they broke - many times
So we switched to "Stress-Proof" steel and never looked back , as they never broke, even though they were lower Tensile Strength
Even head bolts suffer thermo cycles and that can lead to failure
Rich