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Ben Noffsinger

Correcting after a quench

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Hi guys, I THINK this is the right place for this topic.

Yesterday I finished forging out my first PW blade, 88 layers of 1095/15N20, with a 4" blade. I normalized 3 times and didn't get any warpage during the air cool (like I have before on monosteels) and was feeling good about the blade, after the quench however I got a slight leftward curve starting about 1" from the tip. Looking at the blade I feel like it's mostly due to forging the tip out too thin in efforts to get it looking just right...should have left it thicker! But I was wondering if anyone had any tips on straightening the tip. I have used a torch to soften the back and slowly over correct in the vise before, but being so close to the tip and in a narrow cross section I'm really worried about losing the hardening if I try the torch. I thought about putting a wet rag or something all along the edge to try and keep the heat out, but thought I would check with the more experienced folks before I dig myself any deeper into this newbie hole. I feel like its a functional blade regardless, but I want it to be straight! Anyway, here's the best of 20 something pictures I tried to take to capture the curvature....

It's fresh out of the tempering oven with oil still on it, and for reference the width at the bottom of picture is 1/8" or just under.

 

Thanks as always, I never would have thought I'd be tinkering with PW this quickly, but this forum has fed my ambition and understanding at an alarming rate! So thanks to everyone on here for making it such a phenomenal resource.

 

Ben

P5010108.JPG

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Do one tempering cycle in an oven then get a ridged flat metal bar and clamp the blade to it with something to shim the point of the blade enough to slightly over correct the bend and then run it through another tempering cycle. Another method, which has a greater risk of breaking off the tip but one that I have used successfully, is to temper the blade and then very carefully try to cold bend the tip. Apply the force slowly. You could try shimming the back side of the bend with something thin then placing a rod of metal over the peak of the bend on the other side and then slowly tighten the whole assembly between the jaws of a vice.

 

Doug

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Thanks Doug! I haven't tried tempering with it clamped to a straight bar...makes sense!

 

So today I was staring at the blade and decided to get the 8oz. ball peen I use for rivets and very gently straighten it on the anvil, it worked!. I was reading a thread the other day about cold forging blades that inspired me. But I was wondering what negative affects that has on the quality of the blade. It seems like the stress from bending it cold like that would create a weak point, is that something to be worried about?

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Glad it worked for you.

 

Next time, heat it to it's tempering temperature and do the hammering while it's warm. This, apparently, will result in fewer cracks, shears or breaks. Not 100% safe, but safer than cold forging.

 

--Dave

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Yer a brave man there, Ben. Also lucky to have cold forged an untempered quenched blade and got by with it. The fact that it didn't break makes me wonder if you got a good quench on it or if it was a slack quench. If you haven't tempered it already you might want to check out at least the tip with a file and see if it bites.

 

Doug

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It was tempered, I learned that lesson the hard way (more than once, unfortunately I have a thick skull) :) I was still unsure and nervous, but it worked out.

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My mother said that I kept doing things the wrong way and expecting different results because I'm a Dutchman (despite the Saxon surname), others said it was because I was a drunk or something even less flattering. Regardless, cold forging even a hardened and tempered blade can result in a quick design change. You can apply more force in a steady manner, like in a vice, than you can suddenly, like with a hammer, and get by with it.

 

Doug

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Best to do it at tempering temp if you can. I have resorted to all kind of bizarre measures at various times to save a sword that warped. But best to do it warm, all of it, if possible.

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I have been able to straighten after tempering. I use a straightening jig, I overcompensate about twice the warp in the opposite direction put it back at tempering temperature for 20 or so minutes then take it out and let cool. it should straighten first time. Some times it requires repetition moving a little each time. What I like about this method is that you don't have to use any local heat leaving the temper line alone. On small blades I quench out of oven while it is overcompensated into a bucket of water blade jig and all . I talked to Howard Clark several years ago and he said using water isn't necessary that it is mortensite that is dissipating. I don't remember is that was the correct terminology that Howard Clark used but you get the point. I continue to have success using this method on all my knives that are warped and have only had success, no failures.I have once had a very thin ladder pattern damascus blade that was warped like a snake on the edge. I used my jig and overcompensated the s curve in the opposite direction. It took twenty quenches before the blade was perfectly straight. I hope this helps. I have a picture of my straightening jig on Don Foggs web site. Timothy

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I really like the idea of re-tempering while in a jig, I'm going to use that, the hammer approach felt risky but I didn't know what else to do and gaining a respectable amount of patience is still on my bucket list :) Thanks for the tips!

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Here is my improvised straightening jig, might give you a few ideas

 

P1050924.jpg

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That is a great rig Sid, Thanks I will be trying this. Normally i just use a crude set up of Clamps and steel bars.

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i have a foot operated arbor press that is next to the tempering oven and when they come out of quench bent they get tempered and over bent hot to correct the worst get a few cycles of heat bend before they are done mostly dome with blocks of hard wood and a pipe in the die holder

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I straighten blades right out of the quench oil, while still hot. You have about 1-2 minutes to do this before it too late. Blade are pretty bendy during this time.

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I straighten blades right out of the quench oil, while still hot. You have about 1-2 minutes to do this before it too late. Blade are pretty bendy during this time.

 

I do it the same way. But you don't have much time to think, so everything (vise or whatever...) must be ready for straightening. And you need a "good eye" (and also good nerves).

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It is also going to depend on how long you leave the blade in the quenchant. If you leave it in the oil until it reaches the same 120-130° then you may not have any time at all.

 

Doug

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Sid, that is one MONSTER three point straightening jig you have there. Very nice. I drilled holes in the jaws of my vice and fitted pins (much smaller)to use similarly. This whole bid'ness of straightening blades is a dark, esoteric and arcane science. Straightening forged blades that have come out of the first deep anneal crooked or twisted is another matter. I favor pipe wrenches and big hammers on a leather pad on the anvil myself. Steel is tough stuff.

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Right out of quench, it's tree stump/baseball bat time. If it comes back after the first temper, I heat and tweak in the vise, taking it up to no more than a brown. Takes practice to know how much you can get away with before hearing the ping of death.

Edited by Al Massey

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It is also going to depend on how long you leave the blade in the quenchant. If you leave it in the oil until it reaches the same 120-130° then you may not have any time at all.

 

Doug

Yes, I leave in the quench oil 8-10 seconds. Use gloved hands and do it quick . Folder blades are easy, large bowies/fighters not so.

 

Best to normalize and not over heat to prevent warp in the first place. :D

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