Hardening Metal

[KBar]

Does anyone have a good easy method to harden chisels, center punches, etc using a O/A torch and some cooling method ? I once heard about using certain oils.

[JJE]

Me dad said that all there is to do is get it hot and it cool it in brunt motor oil. He said that is what they did at the shop for Delta. Right or not that is what have done to.

[vin-man welding]

just google how to harden metal. and that reply was very well typed.

[Broccoli1]

Me dad said that all there is to do is get it hot and it cool it in brunt motor oil. He said that is what they did at the shop for Delta. Right or not that is what have done to.

One more step- Temper.

Basic breakdown-

Heat & Quench ( water, Motor erl or Veggie erl-- whatever you want to use)
Tool is now Hard but Brittle- Breaks easily

Polish/Sand the Tool- this helps in seeing the tempering Colors

Heat again until tool turns the Color you need for whatever application- Quench- This part is tricky as the temper color happens FAST.

Now the Tool is just right- not to hard and not too soft.

As Vin-Man said- Google has tons of Info.

[Sandy]

Here is the method I use for carbon steel, first preheat the area too 1100ºf (dull red) and let free air cool slowly. This removes any stress in the material.
Next reheat the same areas to a dull red then quench in oil until cool. Used motor oil works well as it adds a small amount of acids at the same time. This method also surface hardens the steel.
Reheat the steel area again too 500º then quench in oil until cool. This quench adds temper to the steel.

Thanks, great answer. I've got some old chisels and punches that need restored.

[KBar]

Thanks Iron Head, Im going to give that a try.

[allessence]

okay, so I'm responding to an older post. Just joined and am a new Miller owner.

Anyhow, my back ground is in the Blacksmithing trade. No, not horses. But working metals by hand with forge and anvil and hammer. I've made hundreds of punches, hammers, chisels, etc.


Heat treating metals. any metals for that matter can be a difficult proposition.

If you buy the material outright you get a spec sheet that will tell you what temp, what fluid or air, and what kind of performance you can expect with what temper.

So, for the most part if these are bought chisels, punches, etc. they are more than likely O1 or A1 or D2.

The first is oil hardening and you can use just about any oil but auto transmission oil has built in cleaners that will help to remove the burnt oil film.

A1 is air hardening and you just bring it up to the right temp and let it cool in a stream of air than polish and temper.

D2 can be W, O hardened depending on cross section.

Hope this help.

[Sandy]

So, for the most part if these are bought chisels, punches, etc. they are more than likely O1 or A1 or D2.

The first is oil hardening and you can use just about any oil but auto transmission oil has built in cleaners that will help to remove the burnt oil film.

A1 is air hardening and you just bring it up to the right temp and let it cool in a stream of air than polish and temper.

D2 can be W, O hardened depending on cross section.

But if you took a chisel out of the drawer with no labels what method would you use?

[Placek05]

I have to agree with the previous posts in regards to the addition of transmission fluid to motor oil for hardening. In my personal experience, straight motor oil can and probably will ignite due to the flash point of oil. I am not a chemist however the addition of transmission fluid did not allow the motor oil to ignite when I was hardening the next item.

Hope this info helps.

[Bryan55m]

kbar....

By using oil Harding tool steel is your best option. This is also know as drill rod or 0-1, quench with salt water or oil (old motor oil is fine) then polish and draw some of the brittleness out of it, usually to a light straw yellowish color.
But if you need to harden mild steel your only option is a case hardening. The Physical properties of mild steel do not posses enough carbon to make it hard all the way through. By using a case Harding process called cyaniding or carbonitriding. There are others but these are more garage shop practical. You can use this application to achieve what you’re looking to do. It is basically heating the material to a given temperature and soaking it in a carbon bath then you will need to polish the material and heat it slightly to draw some of the brittleness out of it, usually to a light straw yellowish color.
I would suggest practicing on a few sample parts before tackling the actual part.
Good luck!