Coffee Can Forge not hot enough

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propane_cooker

Joined
Mar 8, 2017
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Hey guys. I have been lurking here for a while and have learned a pile. Currently trying to make my first two knives. I built a coffee can forge using Imperial Castable Refractory. I got a Mag torch MT245C to use in it. I tried the whole setup last night using propane and could not get my steel up to non magnetic. I'm wondering if i could get some advice on how to improve it. Would MAPP pro be a quick fix to get it hotter? I have a hard (non insulating) fire brick blocking the back. Do I need more airflow? Should I cut a hard fire brick to block half the front off? Is my chamber too big? If some guys could take a look and let me know that would be great. Thanks in advance.

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I'm no expert, but if I had to guess, the problem is that the refractory you used probably doesn't have a high enough of an insulation value. It's really meant to be used in addition to insulated bricks and what not. You might try lining the interior with some cera-wool/kaowool or similar, and even adding an insulating refractory coating like itc-100.

Also, covering the opening while it heats up, wouldn't be the worst idea, though again, I think you're just losing all of heat based on the refractory choice more than anything.
 
You simply don't have enough BTU's. The problem is the Mag torch does not allow enough oxygen to mix with the propane. Go to Harbor Freight and buy one of those cheap roofing torches. Runs off of a propane bottle, and will provide more than enough heat. Or, go look up how to build a powerful torch. (Also inexpensive). Building your own torch, you can design it with or without forced air. Check YouTube for builds.
 
DavidHoback said:
Go to Harbor Freight and buy one of those cheap roofing torches. Runs off of a propane bottle, and will provide more than enough heat.
Click to expand...

yes, this,
here in SoCal it's called a weed burner and it's $25
works great, efficient and has a very fine adjustable dial for flame control
I use this on my small forge for doing small folder blades.
you can also control the heat exceptionally well with this in case you need a soak time

you can see a pic and video on my IG of this burner
 
I did a coffee can forge a few years back, with an old style gasoline blowtorch for heat. Those pour out several times the heat of a Mapp gas torch, and it would just barely do it if I covered the end halfway with a kiln brick.

If you have a Mapp torch and don't mind something smaller, a one brick forge works great. I use mine on occasion for small jobs
 
maybe roll up some kaowool insulation and use it do reduce the interior size to 2 1/2 - 3 inches. with a new burner as those guys suggested you should be in business.
 
Thanks for all the advice everyone. I appreciate it. I cut a hard fire brick to fit in the front and put a notch in it to get the knife through. Got it heated up past non magnetic and quenched resulting in my first hard knife! I see I got a wee bit of a warp in it, maybe about 1/16. Any ideas how to get it out? If I clamped in the vide after tempering would that help? I had done a pile of research on what torch I should get and went with the MT 245C based on a couple of posts I found here. I think the plan going forward is to get some kawool and use that to reduce the chamber size as suggested. Does it need to be coated? I can't even begin to afford ITC 100, any other suggestions? Anyone have any experience with unibond 33 high temp mortar cement https://www.soundingstone.com/colle...gh-temperature-cement-pint?variant=9850962372 ? I can get it from the same pottery outfit I can get the kawool from.
 
Before going too much farther you should take the time and do some reading. The stickys have the info you need for forges, burners, HT, straightening warp, etc. The custom search engine (in the stickys) also will find hundreds of threads on forge building, the torches to use. torch placement ( your ios in too far), and straightening warp.
 
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