# Does all blade warp overtime ?



## Gjackson98 (Jun 18, 2018)

Just out of curiosity, I have been reading a lot of articles about knife blade warping(bending/changing shape) overtime lately. 
Does all blade warp? If they do, what do collectors do to keep it in the original shape; or where do you sent it for fix?


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## Kippington (Jun 18, 2018)

Steel that has been cooled rapidly in the quench will have some parts cool faster than others, I'm sure many of you have seen this:







And with this twisting comes a build up of internal stresses that can either pull or push against each other, or tear the blade apart.






Once the blade has been quenched, tempered and brought to room temperature, we'd like to think that the steel is in a stable state. And for the most part, it is. But because we don't live at absolute zero, there is still a bit of heat around at room temperature that can continue to make small changes to the internal structure of the steel. Enough to sometimes make a knife change shape over time, if only by a little bit.

This phenomenon is well known to Japanese bladesmiths, who sometimes hold huge stocks of forged blanks for a few months before moving to the next stage of grinding them to shape, because they are waiting for the steel to 'settle' into it's final shape.

You could do that, or you could just temper the blade again. By increasing the temperature we accelerate any internal changes that want to naturally happen over an extended period of time.


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## Gjackson98 (Jun 18, 2018)

Thank you for the awesome info!
I wonder how often do people see warping issues in Big name brands.


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## chinacats (Jun 18, 2018)

I'll just add that I own a couple of knives that are over 100 years old and they've not warped.


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## Godslayer (Jun 18, 2018)

I've always thought the rule was single bevel knives are much more prone to warping over prolonged periods of time, I have a 80+ year old Sabatier post WW1 and it's pretty much straight. Sadly I don't have a 80+ year old yanagi but am open to donations.


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## panda (Jun 18, 2018)

they warp when you smash them on the counter


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## Gjackson98 (Jun 21, 2018)

Godslayer said:


> I've always thought the rule was single bevel knives are much more prone to warping over prolonged periods of time, I have a 80+ year old Sabatier post WW1 and it's pretty much straight. Sadly I don't have a 80+ year old yanagi but am open to donations.



I just purchased my first single bevel knife yesterday, hopefully it wont warp...


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## Marko Tsourkan (Jun 21, 2018)

Well, warpage results from tension in the steel, than in turn is induced by heat treating and grinding. It's much common occurrence than many people realize. San mai blades can be straightened, provided that they are not 8mm thick at the spine debas.


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## Matus (Jun 21, 2018)

I had monosteel blades to warp (bend) slightly when ground (and even hand sanded) on one side and then get back straight when the other side was worked on. Inam still not sure whether it was the internal stress as I would not expect much of it in a stainless (Niolox with cryo) blade. But I noticed it with 2 knives I have made.


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## Paraffin (Jun 21, 2018)

Marko Tsourkan said:


> San mai blades can be straightened, provided that they are not 8mm thick at the spine debas.



Backing that up -- I bought a knife last year that arrived with some damage to the package, with the first inch of the blade very slightly bent sideways at the tip. It was Aogami Super with a soft iron damascus (pattern-weld) san mai cladding. I was able to carefully bend the tip back into alignment with just mild repeated pressure under a block of wood. 

It seems that the san mai cladding helps hold the shape? I imagine it would be more difficult for a home user to straighten a bend with the harder stainless steels like PM steel. With any luck I won't ever have to try that.


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## Gjackson98 (Jun 22, 2018)

I guess my next question for you all will be, if i do end up facing this kind of problem and I have no skills, where can I sent my knives to fix it up?


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## HRC_64 (Jun 22, 2018)

the JDM shops do restoration work all the time,
my guess is JKI or similar is also equipped either in house 
or with contacts to do it.


also, check you-tube...


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## Gjackson98 (Jun 22, 2018)

HRC_64 said:


> the JDM shops do restoration work all the time,
> my guess is JKI or similar is also equipped either in house
> or with contacts to do it.
> 
> ...



haha good idea, YouTube always saves the Day.


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