- Joined
- Sep 28, 2014
- Messages
- 693
Hi Everyone,
I could use some clarification on a few details regarding the use of a pipe muffle with a charcoal forge for heat treatment. Let me say up-front that I completely understand this method will never have the same level of consistency as using a HT oven, and that I will be limited in terms of the steels I can successfully harden. I am currently just a hobbyist, so I am planning to stick with 1084 and the like, and just enjoy the process.
I picked up a piece of heavy steel pipe at the scrapyard to use as a muffle. I don’t have my calipers handy right now, but the pipe is probably about 2” ID, with 3/16”-1/4” thick wall.
Here is what I think I understand from searching previous threads. Please feel free to correct me if any of these are wrong:
I could use some clarification on a few details regarding the use of a pipe muffle with a charcoal forge for heat treatment. Let me say up-front that I completely understand this method will never have the same level of consistency as using a HT oven, and that I will be limited in terms of the steels I can successfully harden. I am currently just a hobbyist, so I am planning to stick with 1084 and the like, and just enjoy the process.
I picked up a piece of heavy steel pipe at the scrapyard to use as a muffle. I don’t have my calipers handy right now, but the pipe is probably about 2” ID, with 3/16”-1/4” thick wall.
Here is what I think I understand from searching previous threads. Please feel free to correct me if any of these are wrong:
- I should cap or plug one end of the pipe. I don’t have access to a welder, but I can shape a piece of soft firebrick into a plug.
- The blade is best placed in a spine down, edge up orientation inside the pipe.
- A piece of firebrick or angle iron can be slotted and placed in the pipe to hold the blade in this fashion.
- Some folks put a piece of hardwood, or hardwood charcoal, inside the pipe to improve atmosphere.
- Should the pipe be placed directly on the coals, or above them? If above, then how far up?
- I think I saw something about using kao wool on top of the pipe, or heaping coals on top of it, but I’m not sure.
- Should I move the blade in and out, or just let it sit?
- Is it best if the blade is not actually in contact with the pipe wall, or does that make a difference?
- I read, in the backyard HT sticky, that a short soak time of at least a few minutes is possible with a muffle. How, exactly, is the blade temperature stabilized? By manipulation of the coals and/or airflow, or blade movement?
Forge temp a much higher then temp. for HT 