Straightening, not going so well

Joined
Jun 16, 2012
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First things first, my usual disclaimer. My skill level is beginning noob. I read a lot on here and elsewhere, then play around on the grinder on the weekends ;) I enjoy making things but am not very good yet. Any knife I learn something on is a good knife, even if it goes in the trash bin.

Anyhow... This is a knife I learned some lessons but am not particularly pleased with how it came out. Before I move on, might as well add one more lesson to it and try to fix the bit of warp it picked up being dropped into the quench tank (I redid the heat treat after that). If I can get it straight I'll handle it and use it, if I mess it up worse ill just toss it. Its 3/16ths 1084 with a full flat grind and full tang.

First I put it between two large pieces of angle iron and put a penny at the high spot, then one at either end on the other side. Tightened it down which flexed the blade in the opposite shape of its bow. Put it in the oven at 435*F for two hours (10*F more than first temper) . It laughed at me and snapped right back how it was when cooled and taken out of the apparatus (yes I marked the sides so I wouldn't trick myself). I tried the same thing again with more pennies. Nada. Then I tried it at room temperature with a lot more bend, I worked it up as much as I feel confident doing with C clamps and shims before I have fear of it becoming a deadly projectile if something were to slip (my vice isn't wide enough for a ~10 inch blade). Blade wont take a set, hot or not. I did not try tempering it at the very high bend angles, would that be a bad idea? The only other thing I've read about would be smacking it with a hammer, but I'm not in a hurry to do that. Anything else I should try in the name of learning and experience before I move on?
 
Heat treat again. After quench, you have a little time to straighten. Use gloves and grab blade and straighten checking it quickly. Once blade gets below about 500 degrees it will be too late to tweak it any more. You need to figure out why it warped to begin with. Leaving more meat on the blade will help. Try normalizing before heat treat. Getting it straight during the normalizing. Then proceed to heat to critical and quench. Hope it helps.
 
Instead of normalizing you could do a subcritical anneal at 1200 F . If the blade is already hardened and cold , never try to straighten unless you heat it to 400 F at least.
 
Also, I find that water quenching from a shimmed/clamped temper can help to set the blade how you want it.
 
Also, I find that water quenching from a shimmed/clamped temper can help to set the blade how you want it.

Are you quenching after removing the blade from the clamped position or while it is still attached?
 
I think (dont want to speak for him so wait for him to verify) that Salem is doing it while still clamped. Ive used this method after reading it here on the forums and found it to work pretty good. Had a couple of hard to straighten guys that this worked for.
 
I tried the quench from temper temp while clamped but probably not in a big enough volume of water. The angle iron I'm using is too big for any containers I have so I threw it in the shower and turned the cold water on pointed at it. The mass of the mild steel probably slowed the cooling too much.
I will try that again from 435 degrees again. When doing that method, should you have it clamped how you want it or with an over-bend?

I appreciate the comments on how to do it with a forge / heat treat oven, I just can't try those right away as I don't have my own forge or kiln. If unable to straighten it I may try that when I go to cook my next knife.
 
I often overbend to about the same degree as the original warp. Then quench. This would be on a third temper if the first straightening attempt proved insufficient.
 
I often overbend to about the same degree as the original warp. Then quench. This would be on a third temper if the first straightening attempt proved insufficient.


That is now what I do as well and really made the difference at getting them straight
 
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