Factory Cart Coffee Table - Case Harden Fasteners

[Scott Gibbons]

Good Afternoon Everyone,
I am working on building a factory cart coffee table and I would like to use case hardened fasterns, but I would like to do the case hardening myself. With that, I have a few questions.

Will a simple mapp gas torch work, or do I need to use an oxy/acetlene combo?
What fastener material should I be using? Stainless? Zinc?
What is the best material to quench with? Should I use standard motor oil or is there something better? I realize there will be some trial and error with all of this, but I am looking for a good starting point.

Thanks in advance!!

[Jesse Busenitz]

I don't know how technical/fancy you want to get, but I normally just take a galvanized piece and hit with a ox/propane torch until it gets dull orange and then let it air cool which normally gives it a black/blue color for my rustic projects. Oh and do all of that outside with good ventilation as that smoke is nasty stuff for the lungs.

[Tony Haukap]

...and I would like to use case hardened fasterns, but I would like to do the case hardening myself.
Why?
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Often times I will like to do these kinds of things too, just for the sake of being able to do them and learning something new... but, case hardening screws, unless you plan on doing some machining to them first, I see no point. Especially when you can buy a handful for a few bucks at the hardware store.
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First off, stainless and zinc are the wrong types of steel to try to harden... you need a specific kind of tool steel with a percentage of carbon, some case-hardening compound, a way to heat them evenly and many of these steels will harden with air cooling others will require oil or water quenching - it all depends on the hardness you want in the end.
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It's not quite as easy as it sounds, when you consider manufactures have trouble getting things heat-treated perfectly in large ovens designed for that purpose. I've looked into it and aside from doing some hardening of custom ground tool tips have pretty much decided it wasn't worth the effort.

[Scott Gibbons]

Great, thank you. I will give that a try!!

[Scott Gibbons]

Honestly I have no real reason other than just giving it a try. My grandfather used to build steam engines from scratch when I was younger. Many times he would case harden some of the parts and I always found it facinating. Sadly he is gone and neither my father or myself knew how he did it. I am just curious to see if I can do it and how it would come out. :)

[Ronald Blue]

If you are truly wanting to harden the fasteners the stainless will not work out. The choice of the heat won't matter as long as you can obtain the temperature needed and can then quench the fasteners usually in oil but some steels can be water quenched as well. It sounds to me like you are more interested in the appearance than truly hardening these fasteners. It has been a long while since I was involved in heat treating so a little rusty here but there as I recall is a carbon powder you can apply that helps to get a case around the outside of the piece(s). Some steels just don't have enough content to do it without help and that would probably be most mild steel fasteners. I would suggest googling it because I am sure there is a great deal out there. Good luck.

[Mike Henderson]

Case hardening, technically, is when you have a piece of iron or steel of low carbon content - too low to be able to harden - and you infuse carbon into the surface of the metal so that the surface can be hardened, while the underlying iron or steel remains "soft". I'm not absolutely sure of this process - maybe a blacksmith will chime in - but I think our ancestors used to put the object into charcoal in a burner. The carbon from the charcoal would migrate into the outer layer of the steel. But carbon reacts very easily with oxygen so I guess the process was difficult to do. I have no idea of how it's done in modern times.

The reason for case hardening was to provide greater wear resistance to an object. It was always done after the object had been machined and shaped.

Mike

[dan sherman]

As others have said specific steels and processes need to be followed to end up with a hardened result. My guess is that your grandfather wasn't case hardening the steel but fully hardening it.

check out this video, it will show you what i bet your grandfather was doing.
https://www.youtube.com/watch?v=s9vM6E4TdeM

[Michael Kellough]

It isn't clear what you're trying to achieve.

Read the Wiki article (http://en.wikipedia.org/wiki/Case_hardening) first.

These supplies will help. (http://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/color-case-hardening/surface-hardening-compound-prod27119.aspx)

[Scott Gibbons]

SUCCESS! Not the best picture but I am happy with the results. Thanks again all.
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[Scott Gibbons]

I used MAPP gas to heat the fasteners to a bright orange and quench them in 40wt motor oil. Once that was done, I cleaned them with some dish soap to remove the oil and then dipped the heads in poly. It took about 3 minutes/bolt

[dan sherman]

did you use regular hardware store bolts?

[Scott Gibbons]

Yes, I just picked them up from the local BORG

[dan sherman]

Yes, I just picked them up from the local BORG

Ok, for future reference what you did was oil blackened the bolts. This gives you the color and a level protection, but no real hardening occurs.

[Bruce Page]

That turned out great. Who said it had to be practical - there's nothing wrong with a little experimentation.

[Scott Gibbons]

Ok, for future reference what you did was oil blackened the bolts. This gives you the color and a level protection, but no real hardening occurs.

I was just going for the esthetics :)

[Scott Gibbons]

Thank you! :)

[Myk Rian]

I was just going for the esthetics :)
Should have said that right off the git go.

[Bruce Page]

Maybe it's the summer heat but we all should lighten up a little.