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An economical tempering furnace

Jesus Hernandez

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WHaT!, Inc. Stands for Water Heater "a" Tank, since I seem to come up with ideas based on the use of used water heater tanks. I could not come up with a good word for the "a" in the acronym, so I officially open a contest here for the best suggestion.


The reason for this furnace is simple, I am in the process of setting up a new shop after I moved to VA. Part of this involves making new forges and tools and I did not want to spend close to $2,500 for an electric kiln long enough to temper a sword. So after some sleepless nights rummaging what to do, I thought that tempering a sword is not much different than roasting a pig in terms of heating physics. Although, I admit that it is a completely different thing from the culinary stand point. So why not make a pipe burner long enough to fit inside a water heater tank in turn long enough to fit a sword, hook a gas injector coupled to an air intake (Venturi) to the pipe for finer control and hook this to the propane tank via a regulator and a needle valve for even finer control. Tested it and it worked. Next and more complicated for me (I am no fabricator) was to play around with different configurations for the water tank itself as to how to open the lid, how to support the sword/s and the final contraction/creature was created. For those curious about numbers, I can regulate the temperature between 345 and 666 degrees F. It does require some watchful attention to get the temperature right but it holds the temperature steady surprisingly well for the amount of $$$ invested.















And here it is in its final emplacement atop my heat treating furnace. Aren't they a cute couple? The propane piping allows to run both at the same time. I am using less than 1 psi for the tempering furnace.







Enjoy life!

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That is just too cool Bro!!!!!


Great Job! I knew that would work. Love it.

You make the best pictorials. I love that three temp row.



Mark Green


I have a way? Is that better then a plan?

(cptn. Mal)

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"I thought that tempering a sword is not much different than roasting a pig in terms of heating physics." You make it sound so simple, I love it. Todd

Experience starts when you begin- Pete Culler

Please visit my website


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I have a very similar Venturi pipe burner on my low temp salt pot...it heats the horizontal pot rather than the air...allows me to quench and temper.

You may think about throwing one in there.



Richard Furrer

Door County Forgeworks

Sturgeon Bay, WI

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Cool idea! I would put a steel heat shield between the flames and the blade. I do that with my toaster oven by using the small "cookie sheet" that came with it on the first rung so the blade does not get the direct heat by being over the heat source. It allows only the passive heat to go around the shield to keep the blade at the temp the thermometer says.


I also do that when baking in the oven and never get the bottom burnt on what I'm baking.

Edited by B Finnigan

Everything I need to know I learned from the people trapped in my basement.



I'm out of my mind but feel free to leave a message.

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First of all - that is a very good realization of a good idea.

second - putting it directly on top of the heat treating forge is really inspired!





please visit my website http://www.professorsforge.com/


“Years ago I recognized my kinship with all living things, and I made up my mind that I was not one bit better than the meanest on the earth. I said then and I say now, that while there is a lower class, I am in it; while there is a criminal element, I am of it; while there is a soul in prison, I am not free.” E. V. Debs

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Rick, I thought about using it to heat the quench tanks too.


Brent, a baffle addition sounds like a great idea.


Howard, it did not work the first time around but it was close enough that I knew what need to be fixed.

Enjoy life!

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Excellent work! The pipe burner looks like it worked out well. I made one last year with a single row of holes for heating horizontal quench tanks. It did take a bit of tuning to get an even flame even all the way down the tube. The venturi choke is just open a hair, then the heat can be controlled by the gas regulator.

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Very, very cool, Jesus. I'm pretty much done with my big HT forge (and due to advice given, a little one for smaller blades), yet I have another hot water tank that needs to be made into something. Now, I know it's destiny :)

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  • 2 weeks later...



Many people have espoused using a pan, filled with sand, as a thermal mass to help keep the temperature in an oven more constant. You could make your baffle a shallow pan and fill it with sand. Could be more hassle and mess than it is worth but, then again, might help.



“All work is empty save when there is love, for work is love made visible.” Kahlil Gibran

"It is easier to fight for one's principles than to live up to them." - Alfred Adler

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I have another big water tank just like that. I don't have the urge to start cutting it unless I can get my hands on a plasma cutter or cutting torch. It's too thick to start messing around with cutting discs on an angle grinder.

I want to use it for a HT furnace though, as my 55 gal drum vertical HT furnace isn't getting completely even heat and isn't long enough for some swords.

I also have a ribbon burner made from 2x2" square pipe.

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