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Help fixing a warped blade


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I forged a gyuto blade (210mm-8") out of O1 steel. After quenching, and mid tempering (200c), it was straight. But - by the end of the tempering, after cooling, it was warped - banana style. about 3-4mm off center.

Please advise how to fix that.

I read about counter-bending the blade (3 points) and holding it at tempering temperature. Is it any good for O1 at this stage? How much can I bend? I fear the TING of death...

(cant upload pictures at the moment. will do later)

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I've had success straightening O1 blades with the method you described, I clamp the blade between two pieces of angle iron and use coins as the three points of contact. One coin goes on the apex of the bend, the other two go where the other side of the blade contacts the angle iron. I then tighten G clamps until the apex of the bend is in contact with the angle iron on one side and the coin on the other, for me I found this to be the right amount of counter-bend for the blade to  be straight once re-tempered and cooled. I then re-temper the blade at 200c~ for 2 hours and allow to fully cool before removing the clamps.

Disclaimer: I take no responsibility for any "tinks" that might occur using this process, straightening warped blades is always risky but I've used this method successfully 5 or  6 times over the past couple of years.


Good luck



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I know another maker that made a angle iron frame as you did foundryman. but still used round rods as the 3 points but also instead of using clamps he drilled a clearenc holes on one side and a taped holes on the other and would tighten it up and put it in the oven at tempering temp after it heats up a little he would take it out and tighten the sscrews up and do this little by little putting it back in the oven after each small amount of tightening until the blade was straight then let it sit in temper for another half hour to hour then take the whole thing out and let it cool while its still bolted straight...he says doing it this way give it less of a chance for that "ting of death" this man has been making knives for a very very long time and even tho I have never tried it I belive it works 100% got a lot of good infor from this man

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Thanks guys! It worked. I think.

Why "think"? Here's a little story: There was this guy who was making "shoo shoo" sounds all the time. They asked him why? and he replied "I"m scaring elephants away". "But there are no elephants aroud here" they said. "You see? it WORKS!".

So I coined, clamped, heated and slowly tightened. And it got the plastic deformation I wanted. No ting. But was it thanks to all the trouble? I have no idea.

Also interesting - how far could I have pushed it? there was a slight bend left in the tip, but I chickened.

I think a controlled test is in order.




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The method in your photo is pretty much what I do.  Run it through a temper cycle first so that it is less brittle.  Then clamp it up to correct the bend, and run it through another temper cycle while clamped up.  3-4mm is a pretty big warp, so you may want to take it out in two cycles rather than trying to get it all out at one time.  I usually find that I have to over correct by about the same amount as the warp to get it straight.

I make a lot of 1095/15N20 pattern welded kitchen knives.  Long thin blades seem to frequently need some minor correction so I do this with good results.  I don't work with O1 much, so your result may be different, but I would expect it to work.

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