Trying to help a friend learn. Who is heat treating knives with a propane torch only?

blgoode

blgoode

Knifemaker / Craftsman / Service Provider
Joined
Oct 3, 2003
Messages
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Just seeing if anyone actually gets enough heat with a propane torch only to heat treat a 4" blade. Not using a forge set up but a torch only.
 
I don't think you can generate enough heat so I'm asking propane users.
 
I mean with out using a forge. Is anyone doing that?
 
I've cut and heated metal OK with oxy-propane and air-propane, if we're talking a plumber's torch I'd be very surprised if it could get a 4" blade red. I think it'd be marginal even using a MAPP plumbing torch.
 
I tried it early on.

I was once able to use a 3, maybe 4 of them to heat a 1/2 by 2 steel bar with the blade on top
(did it that way for evenheating)

It took forever & still was very marginal.

next step - I did it with a stack of soft firebricks around it.
 
I have never had good luck way back when and was told to go for oxy/aced and I've never tried since then. Thanks for the info.
 
Use a good heat-reflecting surface. 2 fire bricks in "L" fashion will work. Keep the torch moving for even heating.
 
I had luck on really small knives but nothing of any size really. I got so frustrated with almost getting to temp I scrapped all efforts and bought oxy/aced kit.
 
I've got this idea to put a thick plate on the electric kitchen stove burner, then a blade on top and pile up some firebicks.


I know it will do about 1200F without the firebricks.
( a family member once melted an aluminum pot)

I'm dying to try it, just need a few days where SWMBO won't be home so I have time to clear the smoke, replace the burner and whatever else...

actually I'm waiting until I come across a different stove for free - seems smarter.
 
non contained propane will not get hot enough. As the count pointed out it only gets to about 1200f. Need 1450f. If our friend is using the torch alone then he is only doing a low temp normalizing. I made the same mistake when I started out, before I got the oxy/acet rig.
 
This will get plenty hot and sounds like a jet engine. You can adjust the flame easy enough

image_11749.jpg
 
I use a oxy/propane rig to cut and bend metal, and to do the harding on some blades. I prefer oxy/acetylene though, it's a bit hotting and makes cutting a bit smoother, it's also a bit more expensive but when I don't have the torch set up I run my forge from the 25 gallon propane tank.
 
I use a propane/ oxy setup. I get plenty of heat and its uniform as well. I have different tips for different size blades though. I use a number 4 brazing tip for small thin stuff and move up to a cutting tip for thicker stuff. On the big chopper I just finished, and the bowie I'm working on, I've got a rosebud tip that I use. And I quench in peanut oil. My blades seem to get plenty hard. My diamond stones don't seem to want to cut them too much, even after a double temper at 475 for an hour and a half.
 
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