Badly Warped Blade

Joined
Dec 7, 2000
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5,179
You'd think after doing this so long I wouldn't make so many dumb mistakes - but there you have it. Sometimes I think it's a wonder I've even survived to this ripe age given some of the stupid antics I've pulled.

Anyway, I quenched a long O1 blade, 12" of blade plus 6" of hidden tang, and apparently didn't check it's straightness right then. To top it off, I don't believe I tempered after the quench. But being me I went ahead and finish ground the blade. Then, sitting around admiring one night I noticed quite a curve! Dang! This is pretty pronounced warp, probably 1/8" over the overall length.

So I tempered the blade, finally, and while it was still hot put it in the vise with my three-point bending setup and tried to get it back to true. I've bent this thing probably 1/4" out of straight over a 5" span, and it will not reset.

Because I have so much time in this thing I'm paranoid about breaking it (unlikely, I think, given the high 450 degree temper) if I give it too much bend, but truly it's worthless as it is.

Does anyone have any ideas about a) how far I should be willing to bend it or b) what I might do besides re-HT to get it more amenable to reshaping?

Re-heat treating is mostly out of the question due to the surface of the blade - no way I could match it again to grind out the scale. I thought about using PBC (?) to prevent scale during a second HT, because then I should only have a bit of discoloration to sand blast off. Does that sound likely?

Any ideas are welcome at this point. If I can't find a way to get it straight I think this project will just die as I don't think I'd ever try it again...
 
Joined
Feb 17, 2007
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3,375
Could you do the HT and quench in Stainless foil and when it is say about 750 rip it out of the foil and straighten. The foil would save you from scale and I would think with O1 you would make the quench even in the foil. According to the chart for O1 you have 9 seconds to get it under 1000, 20 seconds to get it under 800 and from there to 600 is another 40 seconds. Thankfully you didn't drop it or hear the pink while you were working it un tempered. Good luck. Jim
 
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Dec 7, 2000
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Thanks Jim, I have some foil and I might give that a try. I'm glad O1 is so generally forgiving!
 
Joined
Nov 18, 2007
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277
Sounds like a great learning experience. Have you only drawn the blade back one time so far?? If so I would suggest a second and third tempering cycle. That should help refine the grain structure down a lot further. Then as soon as the blade comes out from the third cycle, bend it back straight. You should have no trouble getting 1/8" of warp out. I normally put the blade in my finishing vice back to just behind where the warp is visible and work it out to the tip about 1" at a time. This next part may sound a bit harsh!! If the blade breaks, You can inspect the grain structure and do some destruction testing on it. Every time you do the destruction tests on a blade it will make you understand more about what's going on with the steel during the H/T process.
I sometimes think destruction testing is more fun than building a finished blade. But then that's just me!!!

Good luck...

Steve
 
Joined
Jun 17, 2001
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5,705
Dave, My main reason for making such long blades is if I break the tip off or even a couple inches there's still a lot of blade left. I'll just forge another tip and try again. Good luck!
 

Fred.Rowe

Dealer / Materials Provider
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May 2, 2004
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6,823
I say lean into it and test fate a little.

With a blade of that length and that little distortion; while sitting down "lever" the blade along its entire length, using your thigh muscle as a fulcrum. Use a piece of leather in each hand to grasp the blade. One hand forward along the spine the other hand at the ricasso. Apply the pressure, take a look, if you didnt get it the first time just add a little more flex next time till you get it rite. This is a better technique than a three pressure points, system. The energy is distributed along the blade more evenly using your body. I have done many blades this way.
Try it, you'll like it.
Glad to see your putting your skills to work.:D

Fred
 

Stacy E. Apelt - Bladesmith

ilmarinen - MODERATOR
Moderator
Knifemaker / Craftsman / Service Provider
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Aug 20, 2004
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I'm with the other guys. Give it another temper, and just bend it. If it breaks, it was not right anyway.

Steve:
The grain won't get any more refined in a temper. Grain growth and refinement is done at austenitization temperatures (1350-1650).
Stacy
 
Joined
Mar 10, 2002
Messages
323
I had the same delimma lately..i ground a 1/4 inch chopper and it took a warp..here is what i did..put the edge down in a pail of water..took my torch with a med heat welding tip and began to heat the place where it it was warped..i heated and heated and heated til the ol color lines appeared..not the first blue line..the secong gray line..pushed it down the edge a ways and took it out and to the vise..it bent back to true..i let it cool and it held straight..i tempered it again (im not sure why..but it felt like i should) i took the blade out and did some cutting tests and slapped a tree..then slapped it flat on the concrete a few times..all was well..i told the guy i made it for what i had done ..and that the slightest problem id make him a new knife immediately..he has used it extensively and so far so good..good luck to you brother..i know how frustrating this can be..later Luke
 
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Dec 7, 2000
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Thanks guys, this is good stuff. Assuming the blade was truly meant to be, and assuming further that I don't screw it up again and irretrievably, I'll show it here when I'm done... But that's a long string of Assumes! :D
 
Joined
Dec 7, 2000
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5,179
Dave, My main reason for making such long blades is if I break the tip off or even a couple inches there's still a lot of blade left. I'll just forge another tip and try again. Good luck!

Ray, you're a riot! :D But frankly, I don't think you make those long blades 'just in case.' I think you really like long pointy things, like me. ;)
 
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