Quick question:

I am heat treating a 4" blade and do not have a one birck forge or anything like that. I am planning on edge hardening the blade using my Mapp torch. On tests, i am having real difficulty achieving criting along the entire length of the blade at once. Even with sweeping motions, it just doesnt seem like ill ever get the entire length to critical at the same time in order to quench. Can this be done in sections? I mean, can I edge-harden the first 2" of the blade, quench, then overlap that secont with the next two inches, and quench? Or will the second heating basically ruin the hardening that I did for the first section? Is there a "trick" to torch heat treating that I am missing? How do you keep a 3-4" section of edge at critical when the torch can only blast on a 1.5" section at any given time? It doesnt seem like sweeping back and forth ever brings any one area to critical.

This is normal carbon steel.

only if you like warped edges

I am sure that some of the metallurgists will have more to say than I, but this is the problem as I see it. If you successfully harden the forward part of the blade and then heat another section as you mentioned, the steel that is just around the heated area will have varying temperatures ranging to just under critical to about eight hundred degrees. The area that is just under critical temperature will essentially be annealed while the remainder will graduate to whatever hardness eight hundred degree tempering gives your steel.

That is exactly what I assumed as well. I will find a firebrick and make a one brick forge...Unless someone has a suggestion on edge hardening with a torch. Im sure the torch is hot enough and ive heard of people doing up to 5" blades using a torch edge hardening, I just can't seem to keep the length critical all at once.

This is kinda a wacky idea, but it might work...

Get a big ol' quench container, and stick your arm in up to the shoulder and bend your elbow so your hand is right at the surface. Hold the tang so the blade is over the surface and start heating at the plunge line. Once it starts getting up to temp start drifting up a little with the torch, and when your plunge gets to critical start pulling it down into your quench, continuing to heat further up the blade as you go. This will probably be alot less gross in water then in oil, don't even concider a salt tank, LOL.

Well, no promises that this will work but if it does then post and let us know.

edit: the people doing 5" blades with a torch are probably using oxy/acetelene, which gets a good bit hotter then MAPP, and way hotter then propane.

I don't think it will work. Any way you go about it, you'll have a section of the blade that will be soft. If you try to do it in steps (first two inches, then the rest), the section you hardened first will "temper" out completely when your trying to do the other half. If you do the back portion first, then try to keep is submerged while doing the front half, you'll get a "transition line" of soft material about 3/16" in the area of the blade that is at the surface of the quenchant that will run generally from edge to spine.

I have been poor boying it as well , I went to running 2 torches buring MAPP gas... I can finally get the O1 to the temp I need before quenching. Next up is a forge :D

For such a short piece you could probably put it on a piece of refractory and get it up to temp. Get a firebrick from a local brickyard for like 5 bucks and put your blade on it... leave a little sticking off so you can grab it up. Then heat it like you were talking about, waving back and forth. The brick will hold in some heat and give it a surface to reflect off of. I've anealed 10xx steel this way, you'll just have to be quick getting it off the brick and into the quench. By the way, you could also just take that brick and make a 1 brick forge :D

how do you make a one brick forge? i have done a surch but can not find any thing on it.

http://www.anvilfire.com/21centbs/forges/microfrg.htm
Hope it helps.. :D :D
Spring ahead... :101