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Zeb Camper

Best temperature to straighten a katana

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I'm making a katana that has a slight bend in it after heat treatment. This will be my first finished katana, the last one (first one) was the practice blade. I have a nice hamon and am afraid I might temper it right out of the steel. It's made of 1075. What temperature do you guys recommend to straighten this katana at?Thanks in advance :D.

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lately ive been over correcting my warps with the penny jig clamped to a flat bar at whatever temperature i last tempered at and slightly increase the heat by 5 degrees until it is straight. I heard the hot fryer oil at 400 degrees is amazing for fixing warps never tried it

 

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Thanks Gabriel, I will be sure to check into the penny jig, and fryer oil. But I am no metalurgist, and was wonndering more about what temperature will keep the hard steel hot enough to bend and not lose my hamon? I am learning as I go really, I am new to the japanease blademaking game. I have temperd at 350°F on a tanto before, but I didn't have to straighten anything.

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tempering temps wont affect your hamon any 350-500.

The penny jig is pretty simple. Find the extent of the warp and place that portion on the penny, and clamp around it so it bends around the penny essentially. Over correcting the warp. Placing it in the tempering oven at say 375 instead of 350 will allow for an easy warp fix! Hopefully! haha  I have had a lot of luck with it recently

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Thanks again Gabriel! I feel like a total idiot now. I had a blade once that you could see the hamon, but just barely. I just figured I had tempered it too hot :blink: I used a kitchen oven that had a temperature problem. The 350° setting looked like 425°-450° range on the steel.

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Hello! I think you first have to trust if the clay does not fall right in the place where the blade was folded. If it were so and the hard area reaches the back you should normalize and Quenching  again. If you try to straighten in that state it can break.
If the hamon is even, you can heat the blade to no more than 200 ° C and straighten with hammer on wood anvil. That is the traditional way.

Put the blade through the grinding machine and bite with ferric perchloride to make sure the hamon is still there.

Sorry for my bad english, best regards, leonardo

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Hi Peter, I think I understand what you are saying. I think you misunderstood me. My tanto turned out badly, you can check it out under design and critique, it's title is "Trash tanto repurpose". I thought I had tempered the hamon out of it. So, now I am making the katana which has a very nice hamon. I was just afraid I might overheat it when I was trying to straighten it while tempering it. And you're english is phenomenal! The only other language I know is American profanity:lol:

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And I just saw that you signed Leonardo, I'm sorry Leonardo. And thankyou for the advice.

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Thanks for the advice JJ, but Leonardo says no more than 200°C though, isn't that like 400°F? I already straightened it earlier at 350°F. It worked pretty well. Will a higher temp. hurt the hamon somehow? Or, is this just to preserve hardness? I wish I could find more info. on this, perhaps some experimentation is in order. because I wish I still had that "trash tanto" It was tempered pretty hot, you could see a hamon, but it was very faint. At one point it was sanded to 3,000 grit. Still it was hardly visible. Could the difference between a hamon and a temper line be in the temper? High visibility vs. low?

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hamon is created at the quench, 500 degrees F= 260 C is not going to change the hamon at all, just hardness. Larger amounts of stress develop in swords from mass and leverage and need added toughness to compensate

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Ok, thank you guys:D I have been pondering that for a long time. I guess I was worried about something that wasn't even an issue:blink: So, I guess I was lucky I didn't break the sword by tip toeing around my heat. I will temper the sword at 450 tomarrow night. Thanks again! Not sure how many katanas I would have broken before I got this far without the help of this forum.

Edited by Zebulon Camper
spelling

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Tempering at 400 is going to put you at 58 rockwell if your heat treatment was right.
This is a bit high hardness for something that is supposed to flex on contact.
I can't find any info on historic Katana hardness but European swords according to my research was at least low 50's.
 

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I guess I will go for 500° then, the guy flat out told me he would never use it on anything real dense if he used it at all, but I won't sell anything that can't be used. As long as it has the hamon, and it won't snap under the occasional tatome mat (<-- hope I spelled that right), then he and I will both be happy:D 

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Tatami.  And the original idea behind differential HT for Japanese swords, of which hamon is merely a happy side effect, was to create a very hard edge and a dead soft back so that the thick spine would support the otherwise too-hard edge in use.  Traditional nihonto will bend if you get a bad hit on a mat, and in extreme cases the edge will crack right up to the edge of the hamon.  They are not meant to be thin springs like European swords.  They are comparatively much thicker and shorter (usually 3/8" to 7/16" or more near the habaki, compare to 1/4" or less for typical Euro swords of the same period in thickness, and average katana blade length of 24-26" versus rapier and longsword blade lengths of 36-48") and are designed to be a precision slicing implement that will respond badly to poor technique.  Back when this forum was populated by some of the best katana guys in this country (ca. 2003-2009-ish) they often recommended no hotter than 350 degrees depending on the steel.  They slowly left as Don Fogg, our founder, retired and the balance of pros to newbies changed from around 75:25 to 15:85.  It's not that they're snobby, they just got tired of answering the same questions and arguing with the uninformed.  That's why you're stuck with me, who while I am no professional bladesmith and know far less than I should about Japanese swords, still picked up enough to share the basics and, being an academic at heart, still answer the same questions over and over...:lol:

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Thanks Alan! Your the man;) glad I didn't temper this at 500 yet. My gut was telling me not to. As you might have noticed, every spare moment in the past week or so, I have been trying to hoard up as much knowledge on the art as possible. I think I might make the full switch to the japanese style. With the occasional odd piece now & then. You and the rest of the forum have been a huge help, as for what knowlage I can't find, pro's like you (you're a pro, I have seen your pipe hawks) are willing to answer. I hope someday I can return the favor:)

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After re-reading what I wrote, I just want to make it clear that tbere is no slight intended against any member of the forum, past or present (unless you got banned, of course ;)) when I was talking about relative skill levels and willingness to share.  This was the best forum on the net when I was told about it back in 2003, and although a lot of the names and faces have changed it still is!  I like that there is not one guru, but everyone who knows something will share it freely.  That is of great value.

edit: and thanks, Zebulon.  I consider myself to be a competent semipro, in that this is not what I do for a living but I try to do it to the best of my abilities.  Any skill I show is because I have had great teachers and great friends with said skills who were willing to show me a trick or ten over the years.  Oh, and once you've cranked out somewhere over 300 hawks you start to get comfortable with the process.   B)

Edited by Alan Longmire

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Zeb, blade straightening is one of those necessary evils. If getting into long blades, it becomes a necessary skill. I have used gabe's mention of the three penny thing for years and glad for it. My set up uses aluminum posts that fit over the jaws of my bench vice, basically giving me a three point pressure system, two on one side and one on the other to press the peak of the curve with as little or as much force as I need. (Used to have a picture, can't find now). I've used this on fully hardened blades (hamon, no tempering), tempered, and antiques. The key is to get familiar with what you can get away with and you can use this set up to apply very little force, walk away with it under pressure, and come back later to see if it was enough. It can take some time. I also prefer to do this at some temperature, right after tempering or might play a torch over the blade to get up to 300f and put in the straightening jig. Some blades are easy to move, some fight you. Depends on the alloy and amount of hardening. Same goes on with antiques.

whew! Most I've written in a while!

Dan

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Thanks for the advice dan, It sounds safer than my straightening method (2 blocks of wood, and my foot):P I will definitely give it a try on my next one. And it's cool to see someone calling me Zeb. That's what everyone calls me at home. I was going to have Zeb as my profile name, but I just opted for my real name instead. Might look into changing it if I can. Kinda weird having people calling me Zebulon :lol:

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I can change it to Zeb if you want.  We have a couple of other ones, believe it or not!

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12 hours ago, Alan Longmire said:

I can change it to Zeb if you want.  We have a couple of other ones, believe it or not!

Hey Alan, if you dont mind, that would be great! And I saw that. Good to see people giving out decent names now a days :lol:

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Knew I had one here somewhere...

 

IMG_0226.JPG

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Wow, Dan, that's some fancy spacers!  Beats my bent 1/4" rounds to pieces. :lol:

Zeb, you are now Zeb, and Dan above is one of those best katana guys in the country I was talking about earlier...

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Thanks Alan, your the man ;) And holy cow Dan, those are fancy! And the katana looks good too. 

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Pretty easy to make, some 3/8 or 1/2" aluminum saw cut to vice jaw dimensions. Faces are slightly radiused. Inlet some small round magnets. Works good 'cause easy to store near the vice, can put any orientation and slide closer together or further away as needed. 

Thanks Alan, I have gained a lot from this forum. When I grow up (I'm only 53 now) I want to be confident enough to be able to say I'm a decent maker

Dan

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