What's wrong with my Shibata Kotetsu AS 210mm gyuto?

[Carl Kotte]

Yeah this really happened. I have a video it on my phone. I will try to upload it somewhere.

Wow, this sounds exciting!!!

 

[Gregmega]

These knives are so thin it’s not the geometry. Heat treat maybe??

 

[Tonsku38]

Yeah this really happened. I have a video it on my phone. I will try to upload it somewhere.

 

[Carl Kotte]

That mighty pinch of yours really deflected the blade [emoji23]

 

[Tonsku38]

That mighty pinch of yours really deflected the blade [emoji23]

I might have used some extra power to make my point but it also bended in normal use.

 

[Kippington]

My guess is that someone used a dodgy method to insert (and hold) the tang in the handle.
I might be wrong but it looks to me like the blade is staying straight. You can use a ruler to check if the metal itself is bending, or if the problem is happening inside the handle.

 

[Tonsku38]

My guess is that someone used a dodgy method to insert (and hold) the tang in the handle.
I might be wrong but it looks to me like the blade is staying straight. You can use a ruler to check if the metal itself is bending, or if the problem is happening inside the handle.

First I thought that handle was just loose but I'm pretty sure that the blade bended near handle.

Few years ago I also had this kind of thing with Kohetsu AS gyuto. At first the blade also bended near handle but then it was like this.

https://www.instagram.com/p/82N1MIpftc/?igshid=aqh5gemgrksv

 

[Kippington]

Yeah it definitely could be the steel bending. It's a risk you face with thin san-mai blades. Monosteel doesn't have this problem as the knife is more like a spring - they're also much harder to straighten.
Interestingly, the more you bend san-mai, the more difficult it becomes to bend.
There's also the chance you'll crack it, like bending a bit of wire back and forth.

There's a stress concentration where the tang transitions into the machi/neck of the knife. It's very likely the location where all the force is getting directed.

 

[Tonsku38]

I sended the video to Shibata himself and he haven't ever seen it doing like that. Luckily I got mine two bad one returned and got finally good one.

 

[Carl Kotte]

What happened to this knife? Are there any pictures of it yet? I hope it’s cutting like never before!

 

[stephen129]

Sorry, I realised I never updated what happened about this.

So I looked at the choil more carefully and compared it to other choil pictures online and to my Moritaka. It instantly became obvious that the knife had actually been sharpened quite a lot.

My theory is the original owner used it, possibly chipped it by a mm or so, sharpened it all back and then returned it, claiming that the only thing wrong with it was a tiny scratch. Or just used it for an extended period of time, then returned it. I don't know how long you'd have to use a knife to have to sharpen away a few mm.

Cuttingedgeknives obviously failed to actually check the knife for anything else and then resold it as a return. I then returned it and got a refund and bought a new one. Hopefully they didn't try to sell it again. On one hand I can see why they didn't check the knife, if you're told it has a scratch that's all you're looking for. On the other hand I feel like they should have checked the knife in its entirety before reselling it. The new one is worlds apart and is my favourite knife in my small collection.