Oh #$@% - Macro chip on a rather pricey knife

I think some of you guys might find this interesting.
So at work yesterday I was cutting a big wedge of Parmesan cheese in half when I hear a *tink* sound, aaaannnnddddd...


(mildly interesting note: you can see micro and macro chipping in this image)

Ohhhh man
The initial damage to it actually goes a few months back - I received the knife on my birthday and consequently cracked in the blade on the first day due to playing with my new toy while drunk (I'm sure I am not the only person that does that sort of thing on this forum haha!)
The initial damage to the knife was the part of the chip that goes straight up, the curved part of the chip-out is where the lateral force pulled a good chunk out a few months later.



The knife is a Sukenari ZDP-189 Wa Gyuto 270mm at 66-67 HRC. The high hardness of this steel is gonna piss me off now that I gotta take a rather large bit of metal off the knife to remove the chip. I'll try to document my repair progress and post it here if anyone is interested.
Also, before I start repairs, I would happily oblige if anyone has a request for me to test the knife against something they think could potentially damage the edge. I have two of these ZDP-189 knives and they perform very well, so I'd be more then happy to run tests on the edge for you guys so that this thread doesn't give the wrong impression that the steel is too chippy or brittle.

Let me know!

That knife looks quite thin to begin with , for tasks like cutting Parmesan cheese or tough tasks I use an old beater German knife ( a.k.a the kitchens knife at work) or cleaver , sorry to hear about the chip,with the hardness of the steel I recommend you sending it to pro sharpeners ( Jon or Dave) I had a zdp189 knife that had to be thinned , it was PITA, good luck

Or if you repeat the process, in a few years you will have yourself a truly amazing bread knife.

ya i would let someone with a belt fix that for me but im interested to see your work in progress and tools you use to work it over.
before the chip that looks like a great profile. when i first started reading i was thinking no way parm cheese did that but makes way more sense with a previous ding. anywho stuff happens and this will definitely test your resolve. mostly i appreciate you sharing the process

I've always heard not to cut something called winter squash with J-Knives, maybe that would be a good test. Also frozen food.

sadly, I would also not cut cheese with anything over 61hrc

dough said:

ya i would let someone with a belt fix that for me but im interested to see your work in progress and tools you use to work it over.
before the chip that looks like a great profile. when i first started reading i was thinking no way parm cheese did that but makes way more sense with a previous ding. anywho stuff happens and this will definitely test your resolve. mostly i appreciate you sharing the process

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I do have a cheap belt grinder which I will be using for for a good amount of the work. I may as well get most of the job done quickly on the belts, then finish the finer details by hand.

And yeah, I'm pretty certain parmesan cheese would've done no damage to the blade if it was in perfect condition. A previous accidental encounter with concrete is what turned the odds vastly against it holding up to the hard cheese. :O
Funnily enough, my other ZDP gyuto (same knife but in 240mm) fell out of its "friction fit" saya as I was running across the road and hit the tarmac hard. Luckily and surprisingly, no damage to that one at all.
I might be wrong, but going off my experience using and sharpening these two knives I think one of them is at the higher end of the bladesmith's target hardness and the other is at the lower end (they're advertised at 66 to 67HRC). Testing will be done on the harder one of the two, assuming I'm correct.

Fritzkrieg said:

I've always heard not to cut something called winter squash with J-Knives, maybe that would be a good test. Also frozen food.

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I'm not sure about the availability of winter squash here in Australia, but I can definitely find some hard pumpkin. As for frozen food, I honestly can't even imagine a realistic scenario where I would want to do that. Can someone please suggest to me a food item to freeze then attempt to cut? All I can think of is frozen solid chicken thighs, which I already know I will have to resort to using the knife like an axe. Not pleasant.

ptolemy said:

sadly, I would also not cut cheese with anything over 61hrc

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I'll add cheese to the test list too. Although I already know it will pass that test as I've 'risked' hard cheese many times, and the only damage occurred on an already damaged spot. Even with the damaged spot it took many sessions of 'cheese abuse' for the cracked area to chip.


Already there have been some good ideas - keep the suggestions coming! I'll make a stress test video as soon as I can then I will begin repairs (assuming I don't end up snapping the knife! :bigeek: )

Winter squash = japanese pumpkin
Butternut squash = butternut pumpkin in down under

Yikes

I can't think of anything that anyone would realistically cut while frozen. How about really crusty BBQ or hard bread?

Salo (Ukrainian pig fat - a bit like lardo) cuts when frozen.

chefcomesback said:

Winter squash = japanese pumpkin
Butternut squash = butternut pumpkin in down under

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I always use thinner knives for squash or pumpkins, like my 240 Gesshin Ginga. No problems.

Kippington said:

The knife is a Sukenari ZDP-189 Wa Gyuto 270mm at 66-67 HRC. The high hardness of this steel is gonna piss me off now that I gotta take a rather large bit of metal off the knife to remove the chip. I'll try to document my repair progress and post it here if anyone is interested.
Also, before I start repairs, I would happily oblige if anyone has a request for me to test the knife against something they think could potentially damage the edge. I have two of these ZDP-189 knives and they perform very well, so I'd be more then happy to run tests on the edge for you guys so that this thread doesn't give the wrong impression that the steel is too chippy or brittle.

Let me know!

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I have the exact same knife sans macro chip as well as the 240mm W#1 Honyaki gyuto. That's a bummer what happened (I remember the price tag). I've heard it said that Sukenari knives are thin behind the edge, and this supports that statement.

I'll be following this thread as I'm curious to see the progress of the repair.

tjangula said:

I have the exact same knife sans macro chip as well as the 240mm W#1 Honyaki gyuto. That's a bummer what happened (I remember the price tag). I've heard it said that Sukenari knives are thin behind the edge, and this supports that statement.

I'll be following this thread as I'm curious to see the progress of the repair.

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Interesting, I never considered this knife to be that thin, but you're probably right. I guess it's all relative.


Left to right: Sukenari 240mm, Sukenari 270mm (w/ chip), Richmond GT Artifex 210mm (thinned).

And thanks for the info chefcomesback. It will help with the shopping.
I'll try to record a stress test video tonight.

Kippington said:

Interesting, I never considered this knife to be that thin, but you're probably right. I guess it's all relative.

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To be honest I agree with you as I consider my Carter and Takamura knives thin. I know I didn't read that at KKF as there seems to be little info on the Honyaki/ZDP ones here. I like the Honyaki one I have but kind of wish I got the Masamoto HS-3124 instead, but it's been unavailable forever.

that gonna be one hell of a job

This happened to me last year, while halving acorn squash. About six in when I noticed three decent chunks missing from the edge. I went back through the squash, found the "missing pieces" and discarded the squash just to be safe. I was a little pissed but took it in stride and spent a couple days re-grinding and re-profiling the knife. The heel lost about 1.5mm and the belly lost about 3mm +/-. But I was able to maintain the profile of the tip (to about 70mm in). It took some work, but a great learning experience all around.

I also learned that round chips, like the ones in this pic, are a sign of the knife not being over hardened, whereas sharp chips may be a sign to the contrary.

Marc, what knife/maker/steel/HRC was that knife? What do people use for such jobs?

Kato?

mhlee said:

I always use thinner knives for squash or pumpkins, like my 240 Gesshin Ginga. No problems.

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+1. I love how the Ginga slides through butternut squash.

mhlee said:

I always use thinner knives for squash or pumpkins, like my 240 Gesshin Ginga. No problems.

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Sorry I didn't elaborate enough, thin and very hard was what I wanted to say .

That is his Kato western I believe

sadness

marc4pt0 said:

This happened to me last year, while halving acorn squash. About six in when I noticed three decent chunks missing from the edge. I went back through the squash, found the "missing pieces" and discarded the squash just to be safe. I was a little pissed but took it in stride and spent a couple days re-grinding and re-profiling the knife. The heel lost about 1.5mm and the belly lost about 3mm +/-. But I was able to maintain the profile of the tip (to about 70mm in). It took some work, but a great learning experience all around.

I also learned that round chips, like the ones in this pic, are a sign of the knife not being over hardened, whereas sharp chips may be a sign to the contrary.

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well,
if you're in the shits in a pro kitchen, there can be a lot of things you have to cut while half frozen because you or someone else did not thaw it and now theres no time.

Fritzkrieg said:

I can't think of anything that anyone would realistically cut while frozen. How about really crusty BBQ or hard bread?

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I use a mallet and and the boss's knife.

Dardeau said:

I use a mallet and and the boss's knife.

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I actually laughed out when I read this. Haha!

toddnmd said:

Marc, what knife/maker/steel/HRC was that knife? What do people use for such jobs?

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Kato Western handle Workhorse. It was pretty thin behind the edge. But after fixing it, nothing got in it's way. One of those serendipitous kind of sufferings if you will.

I should take a picture of his knife for yall. It is a hattori forum with what may be best described as a whimsical sharpening job. In reality we keep a Henckles around for the mallet jobs.

I just got home from work and I'm too tired to edit a proper video from the footage I've recorded today.

Here's an unedited teaser for what I've got in store. I'll do some proper editing tomorrow.
[video=youtube;1efKHUpCGQA]https://www.youtube.com/watch?v=1efKHUpCGQA&feature=youtu.be[/video]

Dang. I imagine that felt kinda good