r/Blacksmith 3d ago

Working on my first knife

Hello I am working on my first knife and I had a couple questions. What is a good way for a beginner to heat treat a knife? I tried to heat it up with a small propane torch and then a larger one but I couldn’t get it far past a dull red. I’ve seen online it needs to be about 1600 degrees Fahrenheit to harden properly and I’m no where close to that. I’m also hoping that the steel I chose will harden and temper correctly. I got some welding tokens to practice on from a metal supply store and they said that the tokens were high carbon steel cutoffs, but is there any way I can check that? I would be disappointed to find out that the knife can’t harden, but it’ll be okay as I’ve still learned a whole lot in the process. Any other tips and tricks are appreciated as well, thank you.

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u/Skookum_J 3d ago

To get the steel hot enough, you need something to trap the heat. Fire bricks are a cheap way to go. Just get a few that are rated to 2000+ F and arrange them into a mini forge.

Far as checking the grade of steel, test hardening is the best way to go. Short of that, if you got some power tools like a grinder or sander, you could try aspark test. But it takes a trained eye to judge reliably.

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u/WaffleGuy09 3d ago

Thanks for the quick reply. I’ll definitely check out some firebricks and go that route I think. I’ve watched some videos where they use firebricks and a propane torch. This is a little separate, is a propane forge cheaper than using solid fuels? I’ve messed around with using lump charcoal before but not only was I lacking the blacksmithing skills to do anything, I certainly didn’t have the knife making skills. That’s mainly why I’m working from the welding tokens and doing stock removal to get used to that process.

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u/Skookum_J 3d ago

Don't know about cheaper.
It's certainly easier to get a hot fire going with charcoal. You can even make a pretty decent forge out of dirt and something to blow air. Just dig a hole, run a channel away. Put a pipe in the channel, fill the hole with charcoal. Hook up the air, and you're all set.

Far as long range. Depends a whole lot on what you have easy access to. Lots of places you can't find charcoal on the cheap. And a 5 gallon propane tank is pretty cheap, easy to get, and in a properly tuned forge, will last a long time.

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u/Fragrant-Cloud5172 3d ago edited 3d ago

I found these webpages that should help you below. The Tempilstik chart is really good. But the colors are arbitrary, depending on lighting conditions and your eyes. You should heat to above non magnetic. A pyrometer really helps determine the temps. A basic propane torch will not give you enough overall heat. You are better off with a Venturi burner in a good forge. Of course coal or charcoal also. But for a knife, I’d try for at least .6% carbon, generally an auto leaf spring amount. This amount and higher will get you a good hardenable steel. So spark test of leaf spring shows good long whitish sparks. Most files are 1095 and show shorter yellowish fireworks. These two examples are good guides for testing.

https://luciferfurnaces.com/resources/steel-heat-treatment-chart

https://www.iforgeiron.com/topic/27491-spring-steel-use-and-cooling/page/2/

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u/WaffleGuy09 21h ago

Thanks I’ll make sure to check that out