how to straighten out a warped blade?

crimsonfalcon07

crimsonfalcon07

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Dec 27, 2010
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So I've been informed that virtually the entire batch I sent in for HT warped and otherwise got twisted and such. So, I'm in need of some help in straightening it. The reading I've done so far suggests it needs to be heated to over 400 degrees or something? Can anyone help me with suggestions for how to undertake this process, or perhaps be willing to straighten 4 blades for me? I don't even have a vise or heat treat equipment (best I got is my kitchen oven), so this may be challenging for me. Thanks in advance for your help. I've got 3 that are made out of 5160, and 1 out of 1095, if that matters.
 
WTF do you mean that ever batch you sent in for Ht warped? Who informed U of that?
 
Thanks AVigil. I'll have to figure out if I can or should temper the blades again, and see just how bad it is when they get back to me. Hopefully if I have to do it via clamping to something, I can use my kitchen oven or something to bring it to heat? Yikes! I'm worried I'll have to start completely over again on these. It certainly could be uneven grinds, although I felt like these were about as even as my grinds have ever been. This is the first time I've run into this problem so far, and I don't really know what it means, etc.
 
A lot depends upon what they mean by warp. If it's a twist like a pringles chip , oh man. On the other hand, if it's a left or right turn at the tip it may not be so hard. Here are a couple of rigs I've set up, same problem, a lean to one side at the end. You just need your oven.
DSC01685.JPG

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I straighten blades right out of the quench oil, they bend very easy for about a minute or so. After that you have to do something like the post above.

You need to find a different heat treater, or do it yourself.
 
[video=youtube;CL2XxWyVfGM]http://www.youtube.com/watch?v=CL2XxWyVfGM&list=UUGTRbXIkgnnse5SZN9bcAog&index=3&feature=plcp[/video]

Here's a quick vid I put together showing the basic ideas of how I straighten blades...
 
I've never had a problem with the HT service I use so far. Usually he manages to straighten the blades just fine if/when they warp. I suppose if it becomes a consistent problem, I'll try somewhere else, but I've heard of warped blades coming back even from places like Peter's and such. I get the impression that sometimes, it just happens. Thanks for all the feedback; I'll look into them and see if I can't save my pieces.
 
I'm the one who heat treated Nick's blades. I worked with them during the short window between the quench and full hardness but couldn't get them completely straight due to the length and twisting. I got most fo the twisting out but by that time they were pretty much hard. I usually get every blade arrow straight. I don't know if I was having a bad day or what. Sorry Nick.
 
No problem. Wasn't nearly as bad as your email led me to believe. I'll see what I can do with them. Clearly not a common occurrence with you. I'll be sending out another batch pretty soon.
 
I fought blade warp for over 30 years. Believe it or not it is not an act of God, must of the time the cause of blade warp is you the maker, rarely the steel you select but that can be a significant variable. It sounds like you have a friend in Daren, he sounds more than willing to work with you. You are lucky!!

I suggest you talk to him a lot and seek to find the cause of the warp and I believe in the fututre you will be making better blades, both of you will learn. Then you can share what you have learned about the prevention of blade warp.

Should one of my blades warp in heat treat it would go to the testing bin and never be sold to a client.
 
I've done blades like these for Nick before and got them nice and straight. I don't know for sure but I think you are correct Ed. These blades are 24" long double edged swords with a fuller. I'm sure all that was the cause of the twisting and took all the time in the short "window" to correct it and left no time for straightening warpage. I don't try to straighten warped blades once they fully harden unless thay are mine. I broke a customer blade trying to do so and decided I would never do it again. I'd rather send a warped blade back than a broken one. I try to remember to advise everybody that I don't guarantee straightness because of the many variables Ed mentioned. I have to say that H/T'ing so many blades from so many different people has taught me a lot about straightening blades. Most of the time I get em right but every now and then something like this happens. I always do my best. My apologies to you again Nick. Thanks for understanding.
 
This is just an idea, but I wonder if you clamped them to a straight peice of stock and re-tempered if the warp might straighten out.
 
David - You clamp to a straight piece with a wedge to reverse bend the warp. After temper, the warp is usually gone.
 
You can do things to prevent warp like making sure to grind/forge evenly, normalizing or leaving extra stock. Some makers heat treat method only hardens a portion of the blade which would virtually eliminate warpage. After our best efforts, warp can still happen to the even most skilled maker and is usually not difficult to correct. It is not a sure indicator of a bad knife and trashing a blade because of it is rarely the answer, unless you haven't the skill, or desire to fix it.
 
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I do my own heat treat and somethings always take place before hardening. Stress relief at 1200 followed by normalization in two cycles. These cycles seem to head off warp during the quenching. This is true even with long blades.

Have you ever hardened blades that warp and no matter how many times its straightened the warp will return during tempering?

Steels just plain weird.
 
I agree with Fred. I got some .09" 52100 and the first few blanks I did warped horribly. I just profiled no bevel or anything and couldnt figure it out. I read up on it a bit and the next few attempts I did a couple of normalization cycles on the blanks then brought them back up to temp and soak just like before. The result was no warp on 3 of the four blades and the fourth was very minor and corrected pretty easy.
 
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