Hardening or case hardening how too….

[ieezitin]

Hello peoples.

We are at work doing our winter maintenance which involves lining hoppers with heavy 1” AR plate steel. To aid in the installation I cut and make from scrap plate dogs which I weld onto the existing structure and use a large sharp tapered wedge to force the new plate to the liner, the problem with this is that the dog gets gummed up with the tack welds and you are forever having to grind them off, also if you whack the wedge to far you loose alignment and it’s a PIA to whack it back and get just the right tension, a lot of  people cut a purpose made C-Clamp in half weld it on and use the threaded end as the business end this has its faults too and usually its made from forged steel and the welds crack under heavy pressure.

I have come up with my own design of a clamp arrangement that uses 2”x1” flat bar consumable blank as the welded part to the structure ( I have miles of this stuff littered around) when this stuff gets gummed up I just throw it away, my clamping attachment fits to these blanks.

Here is my question, I have a length of round bar 2” dia and I don’t know what it is (spec wise) I want to cut a 1” dia thread (acme) about 6’’ long and from the same stock I can make a female threaded block, now I want to harden them both, I have never played with annealing or hardening steel and would like to know a down and dirty way to do it, I have a fire pit by my barn and copious amount of wood so the heat source is not a problem.

These are my working parameters, I will be applying a Ton of pressure for clamping force via a long leverage bar ( 1” plate does not yield easily)  and it will get considerable abuse, what pitch would be best suited?, do I fully harden or do I just case harden if the latter is best please explain how to do that procedure. And last of all when I cut my thread do I hit the said given tolerances or because I will be hardening them both do I allow a percentage to the given tolerances?.
Many thanks in advance.  I wish to learn     Anthony.

[Jasonb]

You can only harden the actual metal if it has a high enough carbon content so thats really out the window as you don't know what you have.

Case hardening can be done to low carbon steels as it effectively adds carbon to the surface and a little way in. You need to heat your metal to red heat and then place it in the case hardening powder, this can be done several times to get a deeper penitration. There is no need to temper after case hardening as the core will not be brittle

Just one other point a square thread is usually used on clamps not an ACME as the square can take more load.

Jason

[sbwhart]

By the sound of it you want something thats tough not hard, tough can withstand shock loads, hard is usually brittle and won't, Id give what you have a try first to see how it does the job.

look around for something that is doing a job similar to what you want to do, and try it out for hardness give it a bash with a chisel or try grinding it look at the sparks the brighter the sparks the harder the material, then look around for something that you can use for your job that behaves in the same way.

Hope this helps

Stew

[bob ward]

There are heat treatment shops who harden steel for a living. There is a fair learning curve in DIY case hardening, for a one or two or three off its probably more cost effective to get the pros to do it.

[ieezitin]

Jason.

I thank you for the response, I figured we needed the spec,  but as I don’t have it I still would like to give it a try as this is just an experiment and I get a little machine time plus I get to learn a new technique. I chose the acme thread as I have a set of external and internal cutters I don’t for a square thread.

Stew,

I think you are right, tough is what I need that’s why in my mind I thought of case hardening. I have a set of Bessey Bar F style clamps made for welders, in fact I have a set of ( 4 ) - 12” jaw opening and they come straight from Germany and I have a set of (2) – 8” opening made by bessey but manufactured in India, if you try to score a file to either the bar frame or thread on the German manufactured clamps it won’t touch it, but on the India model the thread are not quite as hard and it scores, another anomaly is that both sets have the same diameter  thread ( only difference between both sets is the jaw opening ) the German made clamp while applying pressure will act smooth and seat itself in a sturdy fashion,  on the India model you apply the same amount of  pressure and it starts to creek and whine and as you reach the max pressure it shudders and stops, I never have put a torque wrench on the pair but I can tell you I believe the German model applies and holds more pressure.
Saying all that, this is where I got my idea for my own clamp design and I noticed the properties of the for mentioned clamps and I attribute the differences to the hardening that gives you their variance in performance. If I am missing something please share.

Bob.

Thanks for the information but this is me tinkering in the shop and trying to learn a little on DIY hardening projects i do not want to spend any money, i just want to use what i have

Any other ideas are more than welcome.   Thanks to all again.   Anthony.

[Jasonb]

Your observations would seem right, the softer surface clamps start to gaul and the friction goes up, the hardened threads will slide against each other allowing more tightening force to be applied.

If you really want teh DIY approach the old way was to use bone or leather rather than an off the shelf powder, the part was packed into a container (Large tube) with teh bone dust etc around it and backed in a fire at red heat, the carbon was absorbed into the metal.

Jason

[Jonny]

Anthony can you cut a small area off heat it up and dunk in to something cold. See what happens with a file before and after? Dont worry about temering purely to see whether it hardens.
It wont be anything precise far from it but at least you would know whether it would take to through hardening. If that is the case it could be trial and error diy, too hard or too soft etc bit too risky. If not case harden.

[ieezitin]

Johnny.

Great idea, I have plenty I will cut off a 2” slice and do as suggested.

Going back to one original question I had, when you machine a piece to a tolerance like a thread ( male or  female ) will the hardening/ heating process effect the fit? If so is there a rule to sizing?.

Jason.
I have access to a ton of bones where I live here on the farm , you have given me a little project to do to see if I can case harden that way, I will certainly record my results and let you know.

Many thanks to all for your insights.   Anthony.  God bless

[Jasonb]

Case hardening will add a minute amount to the surface, not really worth worrying about. For something like a clamp thread I would give it a bit of play rather than making it a dead tight fit.

Jason