This works for most carbon steels. Aluminum and stainless steels cannot be heat treated with this method.

Material required:

PPD (personal protection device) Safety glasses, gloves, respirator, apron.

5 gal bucket (2)

Enough fireplace ash to fill one of the buckets.

Tongs to handle hot parts.

Source of heat: acetylene torch, forge, etc....

3 gals of used engine oil.

Pot magnet.

To anneal (soften) first heat the part to red heat. Temperature is difficult to gage so use this method. As the part heats, have a magnet handy. There will come a point that the magnet will not stick any more. Hold this temp for a couple minutess and then cool slooooowly. I find that fireplace ashes make an outstanding insulator. It can take up to 12 hours to cool this way. Take the part and bury it in the dry ashes. Check it in a minimum of six hours. Once it is back to room temp, work it as required and then re-heat treat.

To harden, again, heat the part until the magnet will not stick. Hold it there for a few minutes and then immediately quench it in the oil. Use long tongs for this. It will smoke like crazy so do this outside and be careful of spattering oil. This is why you must wear the PPD. Remember that while quenching, keep the part moving. The heat leaves the part and goes into the oil so we want to keep the heat transfer even. At this point we have a hard part but it is also brittle so we need to temper it. Most carbon steels temper nicely at550 to 700 deg so this can be acomplished in an old kitchen oven. I use one that I tweaked the thermostat on and I get 675 out of it.

 Temper for 30 min for every inch of thickness. Just turn the oven off and let everything come to room temp slowly.

I have employed this method since the 70's when I learned it from and old time blacksmith. Above all, use caution, care and common sense. IF something does not seem right, STOP!! Aare doing and analyze what you are doing so make the corrections as needed.