How do you HT a 42" Katana?

Bruce Bump

Bruce Bump

Joined
Dec 2, 1999
Messages
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My son Brian is here from Portland Ore. and we forged out a nice katana from 5160. I had to take the back door out of the forge to do a blade this long but forging it was easy enough. My worry now is how do I keep it straight through the quenching process. I plan to do a satinite pack on the spine but will this keep the blade from bending from the weight and warping from the quench? I have it pretty well normalized so stress shouldnt be a problem. How do I heat one this long and how and what quench medium do I use? Also If Im lucky enough to finally temper this bad boy What method should I use? It wont fit in the wifes oven.
 
Gee Bruce, I feel stupid telling you how I do it. Kind of like telling Barb Wire how to get dates!:footinmou

I have never done a 42 but I make a number of 39's over the year. Not a whole lot of difference. I heat them in a forge I made using Kaowool lined stovepipe and 2 mini-mongo burners. Just get a tank long enough to quench. DO NOT use a piece of pipe unless it's 6" Dia. or larger. The result of using smaller pipe for the quench tank is called the flaming volcano of death:eek: Ask me how I know:o

If you only plan on doing one sword you can dig a trench, Line it with charcoal or Coal and use a blower to heat it. I did it that way before I came up with the stovepipe idea.

BTW If you don't want to build burners, my first stovepipe used propane torches stuck in 1" pipe nipples that I screwed in the side of the stovepipe. 14 of them if memory serves me.

Oh...the tank I use is a rocket launcher can that I picked up at a gunshow for $2.00 they aren't hard to find and have a top that toggles on so you don't even have to drain it.

Good Luck!
 
Did the Japs temper theirs?? What do I know. I thought they did not temper them but only edge quenched.
 
They did both Rodger. There is a common misconception among the sword snobs that there is only one way to do it. There is as much variation in Japanese sword building as any other type. Many but not all swords were folded steel and the masters were able to combine hard and soft steels in a way that allowed a flexible blade that had hard edge holding brittle steel, sandwiched between the softer steel. When this was clay coated and quenched it did not need to be tempered. They did break more often than people believe though.

Other swords were quenched and tempered the same as the rest of the world. It depended on the maker and cost of the sword.

There have never been any hard and firm rules in swordmaking. Now if you want to hear the other side of this discussion, go to one of the older sword boards, I won't say the name but to give you a hint the "Publisher" his term not mine, has a girls name
:D
They will tell you all about the true way of the Japanese Master:rolleyes:
 
Thanks for the info Peter. I think that if I can make the katana like my ABS test blades, You know.. quenched edge, soft spine, spring temper down the center I would be happy. The problem I see is the length of everything such as the heat source, quench tank and tempering a long blade in an oven. Why cant i clay coat the spine and run the blade through my forge in and out until it is nonmagnetic and quench in a 6" pipe full of warm oil horizonally? Will the blade warp from its own weight or will the clay coat keep the steel cool enough to hold its shape. Is that the real purpose of the clay?
 
Why cant I clay coat the spine and run the blade through my forge in and out until it is nonmagnetic and quench in a 6" pipe full of warm oil horizontally? Will
I expect YOU can Bruce. I've tried it and was never able to keep enough heat to eliminate all the soft spots. That is a matter of skill (or lack thereof) and I suspect you may have better luck than I.

Will the blade warp from its own weight or will the clay coat keep the steel cool enough to hold its shape. Is that the real purpose of the clay?

It's like anything in knife building Bruce, just bigger. Sure they warp sometimes although they can be straightened most of the time. Clay coating adds another dimension to the operation though. Done properly, a well-coated blade will curve some. Some of the curve in a Katana is forged and some of it is differential cooling. If there are other stresses in the steel, the blade will tend to twist as well as curve. Again, this can almost always be corrected after HT, it's just hard on the blood pressure.

If I were doing it I think I would pass on the clay. 5160 doesn't give a great Hamon and it is just one more thing to worry about. I wouldn't recommend this to many people but you have a good enough eye to draw temper it using a propane torch. Just heat from the spine and watch for your straw on the cutting edge. This should give you a good edge with flex.

Another option if it doesn't have too much curve is to put it edge down in a water container of some sort and use the torch on the spine. I did this in wet sand once and it worked pretty well. The wet sand trick will also work for a water quench.

I just thought of one more way you can temper it without a lot of setup. If you have a hotplate, you can take your stovepipe and set it end down on it. Hang the sword in the pipe and use a thermometer to regulate the temp inside. Cover the top with heavy foil. This also works if you need to bake epoxy paint like Brownells sells, on long pieces like sword sheaths!
No need for the Kaowool to do this!
 
Peter these are all good ideas, especially the stove pipe on the electric burner for tempering. I love that one and will use it. I still want to clay coat the spine. It should keep the spine cooler and add stability to minimize warping. I hope I have it normalized well enough but since you mentioned forging in some curve I think we should forge in some more and normalize again. It is almost straight at the moment and was hoping it would curve with the HT. As far as a Hamen line I dont care. Next time maybe. What is your favorite method of straightening a bend or twist after HT.
 
What is your favorite method of straightening a bend or twist after HT

I have 3 pieces of 1" aluminum round about 4 " long. I use them in the vice like an arrow straightner. Go to the apex of the bend, place 2 of the pieces on either side of it and the third on the apex. Put it in a heavy bench vice and put mild pressure on the 3. I do it in stages using just enough pressure to do the job. If the bend is a long one, go on to the next part of it.
Your son is a lucky kid!
 
I'm with Peter, Bruce as far as forgetting the clay. On any blade the clay will work alright to keep the spine cool, but on a blade that long and using the forge in and out method the clay coated spine will draw heat to quickly from areas before you can get a good consistant heat the entire length. Just my opinion. As for warpage the blade will turn up some when edge quenched coated or not, you know as well as me to try and keep the blade turned up on edge when heating and keep that sucker movin. I can't wait to hear how this comes out, I've been wanting to make a two handed broad sword, but haven't because of the heat treating issue.

Good Luck,

Bill
 
Bruce and all,
I took a class with Don Fogg and Chuck (can't think of his last name) at JC Campbell on making a katana. The steel was 1065 I think. What Don and Chuck had rigged was a forge with sand in the bottom with a temp sensor in the sand that controlled the gas. The cycling didn't work very well because it was a blown forge and , although the gas was shut off the blower continued cooling the forge too quick.
The hardening was done in water that was slightly heated. I assume that the violent cooling was desired because the curve was needed.
I did the cooling, about 3 seconds in the water, then out for 3 to 4 seconds then back in the water for 10 seconds or so.
Chuck took my blade to the anvil before it completely cooled and did some straightening with a hammer.
That method seemed to work well for Don and Chuck but I don't have their experience or expertise. I'm building another forge to use some of his methods. I have a length of 3" pipe that I will cut a slot in the top and fill with sand. That pipe will be suspended in the forge, horizontal not vertical like my present forge, and heated with a couple of naturally aspirated burners. Because I like 5160 also I will use oil to quench.
Does that sound like a workable plan? I welcome opinions, especially criticisms, because it's still in the planning stage.
Lynn
 
Clay coated blades quenched in oil curve down not up. They only curve up in water.

You can vertical quench a long blade, I have, but horizonal it better and easier. 42" of hot steel in a 50" vertical pipe...you better have long arms ;)


I think you will find that just as forging the longer blade was more of a pain but basicly the same as a shorter one, that heat treating it will be the same but more of a pain.



Seth
 
You might check the late Bob Engnath's site, he did the sword heat treat thing. I forget how much detail he related.
 
Bruce,

Wally Hayes has a two video set from Paladin Press that details the making of a katana. He details clay coating, heat treating and tempering with readily available methods. He also covers handle wrapping and scabbard making. It is a great and informative video set.

John
 
Hey Bruce-

Just come over and use my 50" deep salt bath.


HAHAHAHAHAHA, I wish. :D

I agree with John, that video set is great. If I could find the damn think I'd let you borrow it. I probably loaned it out and haven't gotten it back yet.

The major hang-up there, is Wally uses 1050 in the video, and that's a vastly different beast than your 5160.

I don't think the clay is a problem, it's just not as beneficial on the deeper hardening steel.

Also, what Seth said is right on. Oil can cause down-ward curvature. It's water that causes the upward curve. I took a test blade and oil quenched it 9 times (out of the salt bath into Tough-Quench) and it looked like a boomerang by the time I was done.

Nick
 
Both Nick and Seth are right (depending on the oil) about the downward curve. I had to go back and re read your posts because I assumed you were talking about a water quench. If you decide to quench in oil, I suggest an even bigger pipe 10" or more or a trough. The flaming volcano of death is bad enough when you get boiling water spewing out but if you get flaming oil all over the shop floor, it gets interesting. Ask me how I know about that too!:o
 
One of the coolest parts of Haye's video of the 1050 katana, was that the clay coated blade bent downward on the first quench and then traversed up a good 2 inches or more on that final quench in the water to give the rearward curve at the point. It is one of the coolest vids I have ever seen with heat treating.

I'd strongly recommend that video, it is one of the most informative I have seen, especially full of hints critical to making a sword.
 
Hey Bruce, you might want to do a little research on clay coating 5160, seems like I read somewhere (perhaps on Swordforums?) that the clay coat heat treat on 5160 might cause a blade that breaks out all along the hardening line (due to 5160 being a deep hardening steel).
I'll try and find that reference. Good luck on the heat treat!
 
OK lets summarize and scrutinize:

Is this going to work? Grind off all scale and grinder marks, Straighten while normalizing at least 3 times and untill straight, Clay coat on the spine and sides very close to the edge about 1/4" Heat the blade in a 48" long pipe with the pipe going in both of my forges hooked together with the back doors off That should heat about 36" at once, I figure I can move it in and out and get a good even heat) One end of the pipe will be welded shut so oxydation will be minimized, A pyrometer inserted in the pipe in a couple different places to adjust the forgesto assure 1450-1475 deg. work in the dark to see the colors better, Soak for about 3 after nonmagnetic, quench in a 6" pvc pipe horizontally filled with warm 150 deg. water, Hold it in for 3 seconds out for 3 seconds back in for 2 seconds out for 2 and back in to stay. Remove the clay quickly and temper in the vertical stove pipe at 400-425 deg. for 1 hour 3 times. straighten as needed with the vice and round rod method.

What have I forgotten or left out?
 
Bruce,
Sounds like a great job of putting everything togather! One note: strighten while warm. Come to my shop and see the broken blades nailed to the wall where I didn't take that good advise.
Lynn
 
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