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how to build a tempering oil bath pipe with temp gauge
- Thread starter DaNoog!
- Start date
A.McPherson
Knifemaker / Craftsman / Service Provider
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- Jan 27, 2012
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You doing electrical or gas heating?
Yes. lol. thats a great question and im not tied to an answer though im marginally leaning electrical.... unless the sage wisdom around these parts seems to lean the other way. Ideally i'd build a salt pot with temperature controls, two of them, one for each task, but im not experienced enough to do that.
So i figured a semi-permanent way to heat up a tube full of oil to 450-ish for a 5160 rapier blade is the way to go? Someone commissioned a rapier from me. never made one due to length related issues with tempering them.
Help lol
A.McPherson
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Well, I've never made one either but if I was going at it from the electrical side, I'd start looking at submersible heating elements and PID's.
If going at it from the gas side I'd look at the articles in the stickies on how Stacy makes his heat treating forge. I think of you made something like a vertical forge, with a big cylinder of oil sticking out the top, it might do the job...
If going at it from the gas side I'd look at the articles in the stickies on how Stacy makes his heat treating forge. I think of you made something like a vertical forge, with a big cylinder of oil sticking out the top, it might do the job...
have you ever made a rapier blade out of 5160? how do you temper something so long?
A.McPherson
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Nope, the longest thing I've ever made was a big ol' saex, about 15" long or so...
I think your plan to make a tempting bath isn't a bad one...
That's one of the fun things about metal working, need a tool? Make a tool!
I think your plan to make a tempting bath isn't a bad one...
That's one of the fun things about metal working, need a tool? Make a tool!
Some years ago I was plaining to make one . I do some research about tempering oil bath and give up .Not simple to do . Most challenge was that oil need to be stir all time .Oils suitable for this are expensive, and unavailable in my area . And they have limited use, high tempering temperatures / 450-550 Celsius / are unattainable . Anyway , It can be done of course .
hugofeynman
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- 932
These guys use sand bath heat treatment:
. Maybe they can give you some orientation.
What would you use to heat treat that long rapier ?
Stacy E. Apelt - Bladesmith
ilmarinen - MODERATOR
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You can't use just any oil. It has to be a certain type of high-temp oil, or it will easily burn your shop down.
I think it would be safer, cheaper, and simpler to make a sword tempering oven. It is basically a simple low-temp HT oven. No need for bricks, just a good layer of insulation around a tube that will hold the heat. I think the tube could be a piece of clay type drain/sewer pipe. You could mount either heating coils or quart rods down the top of the pipe. A simple, PID controller and SSR would finish it off. Add a circulation fan if you want to get fancy.
Now, all that said, here is how I temper sword blades in my gas kitchen oven with the oven pre-heated to 450°F.
I place the blade in from the top front right corner to the bottom back left corner. The extra length sticks out the top corner. I use some pieces of kao-wool to wrap the exposed tang and close up the small gap in the door and a wad at the back corner where the blade tip rests. I temper for an hour, flip the blade around and temper another hour, cool the blade off, and repeat that again for the second temper. In my kitchen stove, that will put almost 36" of the blade in the oven. On most swords that is the whole blade area leaving only a little tang sticking out. I draw the tangs back with a torch anyway to get a lower hardness there.
I have a multi-probe meat thermometer that I used to test this out. I put a bar of steel in the oven with three probes wired onto it near the ends and the middle. The unit showed a little hotter at the back corner and a little cooler at the top corner near where it was sticking out. but the overall difference wasn't significantly large. IIRC., it was less than 20 degres between the extremes, with the center at the desired temperature. So, it was tempering in a range of 440-460 degrees. I suspect that is more than accurate for the tempering of most swords.
I have a big digital controlled electric convection oven I bought NIB at a flea market for $50 that I will eventually put in the new shop for tempering. I will cut or drill a hole in the corner of the door so a sword blade could stick out with the door fully closed. That would only require one piece of kao-wool to wrap the exposed end and close up the small hole where the end sticks out. When not needed for tempering a sword I will plug the hole with a wad of kao-wool.
Think about the possibilities of putting a used stove or in-wall oven in the shop. You could do tempering of knife blades in it. You could modify the corner of the door so you could do swords. If it was a stove, you could boil blades to neutralize them after an FC etch, simmer a big pot coffee etch, or make a pot of tea. It will also keep the wife much happier without the post quench fumes in the house. It can be an electric stove that plugs in to your welder socket, or a gas stove running on Natural Gas or Propane.
Just some ideas for you folks.
I think it would be safer, cheaper, and simpler to make a sword tempering oven. It is basically a simple low-temp HT oven. No need for bricks, just a good layer of insulation around a tube that will hold the heat. I think the tube could be a piece of clay type drain/sewer pipe. You could mount either heating coils or quart rods down the top of the pipe. A simple, PID controller and SSR would finish it off. Add a circulation fan if you want to get fancy.
Now, all that said, here is how I temper sword blades in my gas kitchen oven with the oven pre-heated to 450°F.
I place the blade in from the top front right corner to the bottom back left corner. The extra length sticks out the top corner. I use some pieces of kao-wool to wrap the exposed tang and close up the small gap in the door and a wad at the back corner where the blade tip rests. I temper for an hour, flip the blade around and temper another hour, cool the blade off, and repeat that again for the second temper. In my kitchen stove, that will put almost 36" of the blade in the oven. On most swords that is the whole blade area leaving only a little tang sticking out. I draw the tangs back with a torch anyway to get a lower hardness there.
I have a multi-probe meat thermometer that I used to test this out. I put a bar of steel in the oven with three probes wired onto it near the ends and the middle. The unit showed a little hotter at the back corner and a little cooler at the top corner near where it was sticking out. but the overall difference wasn't significantly large. IIRC., it was less than 20 degres between the extremes, with the center at the desired temperature. So, it was tempering in a range of 440-460 degrees. I suspect that is more than accurate for the tempering of most swords.
I have a big digital controlled electric convection oven I bought NIB at a flea market for $50 that I will eventually put in the new shop for tempering. I will cut or drill a hole in the corner of the door so a sword blade could stick out with the door fully closed. That would only require one piece of kao-wool to wrap the exposed end and close up the small hole where the end sticks out. When not needed for tempering a sword I will plug the hole with a wad of kao-wool.
Think about the possibilities of putting a used stove or in-wall oven in the shop. You could do tempering of knife blades in it. You could modify the corner of the door so you could do swords. If it was a stove, you could boil blades to neutralize them after an FC etch, simmer a big pot coffee etch, or make a pot of tea. It will also keep the wife much happier without the post quench fumes in the house. It can be an electric stove that plugs in to your welder socket, or a gas stove running on Natural Gas or Propane.
Just some ideas for you folks.