forge muffle questions

H

Hesparus

Joined
Oct 31, 2004
Messages
1,442
Hi Everyone,

I want to try using a muffle in my charcoal forge and I have a couple of questions about it.
1) I know that using galvanized pipe is a bad idea, but I have easy access to some. Would it be possible to put a piece in my forge and leave it outside while running and burn off the galvanization?
2) Does the orientation of the blade in the muffle matter? I seem to recall seeing people with some kind of device that keeps the blade straight up and down.
If anyone has any other tips about using a muffle, I'd love to hear them. I already know the one about putting a piece of charcoal in it to reduce decarb.
Thanks,
Chris
 
Well, it has been a while since I used a muffle. I would strongly recommend that you stay away from galvanized anything.

You can buy square or rectangle tubing relatively cheap. I would recommend wall thickness be a minimum of 3/16 thick. The "fire" end needs to be closed. You can either weld a plate over the end or cut/file a piece of soft fire-brick to close it off.

It takes longer for your blade to get up to temp, as the muffle has to first come up in temperature, then the heat is transferred to your blade.

Again, soft fire brick cut/filed to size with a cut in the center will assist you in keeping your blade upright.

You will find that the muffle will deteriorate over time, but you should get many uses of it before you have to replace it.

Muffles are one means to avoid direct heat/flame on your blade and will assist in a more evenly heated blade, however, if you do not have a method to measure the actual temperature of the blade............. Well, you know the rest of the story...........

Hope this helps a bit.

Robert
 
A muffler makes sense when using an uneven heat source like charcoal, as the steel walls distribute the heat more evenly internally, allowing your blade to come up to heat without undue hot spots. I've never been sure exactly what putting wood chips in does, but it can't hurt. A peice of angle iron with a slot cut in can be used to position the blade. I've always placed the blade edge up, just my preference. As Robert said, a fire brick can block one end, allowing for better heat/retension of heat.
The only other thing, when you have a lot of red hot coals, heap them over the muffler and apply the air, a lot of air! You'll have to work hard to get the whole thing up to heat. It's a lot harder than simply putting the blade in the coals and going at it. Robert is right, of course, other than eyeballing, there's not really a way to know what temp your blade is at, so the only solution (that I know of, anyway) is to keep checking it with a magnet. When it's nonmagnetic, ready to be quenched (although it's really not that simple either). In any case, it's old school, fun, and men have used coal and charcoal forges for many centuries and turned out fine, workable blades. And before guys jump all over me, obviously, a properly controlled forge is preferable.
 
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Thanks for the tips!
I currently do all of my hardening in a charcoal forge without a muffle. I've gotten pretty good at controlling my temperature, but I've been having a problem getting longer blades (above about 6") to heat evenly — since I'm getting more into kitchen knives, this is especially important for me as of late.

- Chris
 
Ah, then you are using thinner stock. The primary issue I see is potential overheating. Actually, a muffle should help in that regard. Good luck, Chris.
 
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