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Will W.

Low Tech Sword HT

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Hello all. 

I have plans to heat treat a small(ish) sword some time in the near future. 28 inch blade, 80crV2.

I have no formal setup for effectively heat treating a blade that large, so im going primitive and low tech with this one. 

Im planning on digging a trench and running some piping for air, basically a long, narrow forge. Quench in a tank of oil.

Its the tempering that has me wondering.... hot oil tempering seems dangerous given the fact that my only heat source would be a wood fire, but it may be my best and simplest option.

Is it feasible to use a pan of sand and wood fire?

I realize neither of these methods are precise or perfect, but im working with what i have. 

A lead bath and low temp salts are out of the question for me due to logistical reasons, btw.

Just looking for advice. Any and all is appreciated. Thanks. 

Edited by Will W.
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Hot oil is dangerous, if you can measure and control the temperature you should be okay, however from what I remember most oils start to smoke around 400F. Make sure the oil tank cant be knocked over.

I tried the trench HT before but the holes in my pipe were too far apart, I will try 3-4" next time. I have a couple 16-20" blades that I will heat treat in a trench soon.

You could do wood, but I think the moisture can cool the fire, charcoal would be better. The other day I burned a bunch of branches and sticks and was left with a big pile of embers, they would burn up pretty quick with forced air but I stuck a 3/8" thick naginata in and it got barely red hot with no forced air.. Charcoal would be better, try to get lump oak charcoal, or something other than mesquite if you can because it pops and shoots out lots of little sparks. Dont get briquettes, get lump charcoal.

If you had a big wood fire you could transfer embers to the HT trench, you might be running back and forth a lot. you couldnt sit next to a big enough wood fire long enough to heat a big blade, it would be too hot without 3ft tongs.

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Do you have a gas grill?  A blade that size would fit in the last few grills I have owned.

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I used a trench for years.  Big pipe, 2" I think, with 1/2" holes every two inches.  Lump charcoal.  Tempering is the bigger problem.  I used a plumber's torch and Tempil sticks, several repetitions to make sure of no retained austenite or untempered martensite.  A pan of sand in a big gas grill as Brian suggests would be far better.  Shoot for 500 to 550 degrees.  At the last sword Ashokan, someone was tempering 1095 swords by basically deep-frying them in the fire pit.  They had a long steel trough full of peanut oil they put to one side of the bed of coals, and kept checking the temperature every few minutes.  Worked really well, and since it was on the ground in a designated fire pit, there was no worry about setting anything on fire.

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3 hours ago, Alan Longmire said:

They had a long steel trough full of peanut oil they put to one side of the bed of coals, and kept checking the temperature every few minutes. 

This is basically exactly what i was planning on doing. 

I was hoping for about a 550 F temper,  which i know is well above almost all oils smoke points, and into most of their flash points. Really dont want a fireball lol. 

Brian, i do not have a gas grill. Well, i dont have one that works anyways :wacko:.

Steven, i should have specified better, my plan was to burn wood in the same pit as the tempering tank and move the coals over to the tank of oil/sand. So essentially using charcoal, yes. My charcoal retort is down for the time being, so im stuck buying charcoal, but i have plenty of wood. 

The normalizing and quenching in the trench will be using charcoal, of course. 

Thanks for the suggestions, guys. 

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Get thee to a farm store and buy a couple gallons of vet-grade mineral oil in the horse section.  It has a much higher flash point than any veggie oil.  Although any oil at 550 is a fire waiting to happen.  Just have it in a pit away from buildings so that if it goes up there are no worries about letting it burn itself out.

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You can also have a lid over most of the oil tank during the temper, so that if it does catch fire you have a smaller hole to smother.  Don't seal it to make an explosion though!  

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17 hours ago, Alan Longmire said:

Get thee to a farm store and buy a couple gallons of vet-grade mineral oil in the horse section.

Roger that, ill see what i can come up with. Thanks Alan.

Jerrod, good point. Even a piece of sheet metal with some holes drilled in it for venting and a thermometer would be better than having the whole thing open.

Thanks. 

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I add an extension to my forge for long blades.  My forge is about average in size for a one burner forge and has a pass through port in the back that has a removable piece of insulation when not used .  I built an 18" extension that is nothing more than a piece of sheet metal made into a tube like shape and lined with 2" of Kaowool and refractory cement.  I just butt the extension up to the front of the forge (which covers the forge opening) and crank the PSI up a little more than normal so the flames shoot out from the extension.  I run the blade from the back side into the forge and the extension keeps the heat at the swords tip enough to heat over 30" of blade.  With running the sword in from the rear of the forge, I can more easily prevent the blade's tip from overheating.  I'll try and snap a photo of it tomorrow or Saturday when I get the chance. The photo will probably make more sense than my ramblings.  The extension also keeps the wife happy because I don't have to dig up a part of her garden for the tried and true trench method.  For tempering I just run the forge at the lowest PSI it will handle and run the blade back and forth across the opening, using a digital temp gun to constantly check temp - not efficient, but it has worked for me.  I'll have to try the sand in a pan idea - it would definitally make maintaining an even temper easier than what I have been doing..... so much for keeping the wife happy.

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