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C Spanner (Case Hardening)

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sbwhart:
Hi Chaps

I was going to put this as part of my Loco build, but thought it made a nice mini project and bring in the topic of case hardening.

C Spanner

The gland bolts on the steam chest of my Loco build, when assembled won’t be very accessible, they have two cross screwdriver slots with the slide valve rod running through the middle. Adjusting them without damaging the screw will be difficult and replacing them will be a complete strip down job, what’s needed is a bespoke C spanner.

I’ve made the spanner from some ¼” mild steel plate, that I’ve case hardened.

Mild steel has a low carbon content and can’t be harden, but if you soak the material at temperature in a carbon rich environment the surface of the material takes up the carbon allowing the surface to be hardened:- this is case hardening. In the good old days this process was used a lot particularly in thing like shafts where you could have a hard wear resistant surface but with a tough core.

What you need:-

1:- Gas burner.
2:- A hearth.
3:- Case hardening powder, I got mine from www.chronos.ltd.com in the UK.
4:- Quenching water or oil.



Method:-

1:- Machine the spanner to the finished shape.



2:- Bring it to a nice bright cherry red on the hearth. Tip:- try to do this in natural light to get the true color.

3:- Bury it in the hardening powder and leave it there to cool.



4:- Remove it from the powder, leaving all the crusty powder on it, and bring it to cherry red again and hold it at this temp to burn the powder in a bit more.



5:- Quench in the water.

6:- Clean and polish

Job Done  :thumbup:




Quick check with a file and you’ll find it skids over the surface

This is the way I do it some of you Chaps may have better ways but this works fine for me. :headbang:

One final thing don't set fire to your shop   :hammer: :zap:

Have
 :wave:
fun

bogstandard:
Nice write up Stew, spot on process.

I would just like to add a comment because of a safety issue with case hardening powder.

Case hardening powder, if stored in nice dry conditions can last for many many years.

'Kasenit' or 'Casenit' is a trade name that is used in the UK, and has been called that for as long as I can remember.
So any of you older ones, or ones of you who have inhertited some case hardening powder from long ago, no matter what the name, should dispose of it straight away, do not even open the tin.

Early versions of case hardening powders contained fairly high quantities of cyanide, and we all know what that does. The later versions that have been available for the last few years are safe, as long as you follow the safety guide that comes with the product.

I have no idea how long ago the formula changed, but to be on the safe side, I personally would dispose of any you even suspect of being rather old or from unknown sources.

Then go out and buy some of the modern formula.

Sermon over.

John

sbwhart:
Hi John

Thanks for the safety reminder, I'd forgotten  :scratch: that cyanide was used a few years ago, the stuff I use is only a couple of years old so will be OK.

Cheers
 :wave:
Stew

SPiN Racing:
Very very cool :)

I was wondering how to harden things.

SOme of the internal parts on the Mazda, need to be hardend for the higher RPM race engines.. like the gears the rotors rotate on.

Very cool stuff.

Brass_Machine:
Thats pretty neat. I have always wondered about the process.

Eric

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