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

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Dardeau said:
Dang. I imagine that felt kinda good
Click to expand...

Yea it feels kinda like gambling haha

While I'm doing this I'm placing a lot of faith in the maker of this knife, his heat treatment methods, his choice of steel, even my own sharpening abilities to a small degree. But despite all this, there's always that small moment of fear as the blade hits that I've made the wrong bet...
 
You said you have a belt grinder , be careful not to overheat the blade especially near the edge during repair . If you don't have variable speed control you will only have split second on each pass before it turns blue ( blue = bad , very bad)
 
Can I suggest trying frozen cheese cake?
 
Do not use a belt grinder at all. Consider it a lesson in humility. You abused the knife, now endure the abuse of repairing the chip. You are going to lose blade height. There is no way around it.
 
If you are offended with what I'm doing to the knife in this thread, I respect your opinion and understand your attitude.

However...
CutFingers said:
You are going to lose blade height. There is no way around it.
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Repeating this information back to me like its something I wasn't aware of tells me you haven't read or understood the first page and first post of the thread.
 
I have a new video uploading now. It will feature a 4.3kg wedge from a wheel of parmesan cheese.

I'll have a link ready when I get back from work tonight.
 
Short derail...
The boss's knife
ImageUploadedByKitchen Knife Forum1426680871.750531.jpg
He's good at many things, but sharpening isn't one of them.
 
looking at the content of the steel ZDP-189 it's very understandable it can't hold a thin edge very good... 3% carbon:bigeek: and 20% Chromium a little Molybden Wolfram and a tiny pinch of Vanadium of only 0.10% makes the grain size in that steel HUMUNGUS :scared4:

Heat treating such blade before hardening is very important and it might have worked better with a high temp tempering of 500-530Celsius 3x1hour after heat treat due to high Chromium, Molybden and Wolfram content. it would loose some of it's rust inertia tho, a little late for that now:D
 
ptolemy said:
sadly, I would also not cut cheese with anything over 61hrc
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This one's for you!

Parmesan cheese with a 67HRC knife

[video=youtube;bXT9yAPVtac]https://www.youtube.com/watch?v=bXT9yAPVtac[/video]

I'll post more soon.
 
It makes me cringe when I see people cutting cheese without a folded towel over the tip.
Other than that, keep the videos coming!
 
Yeah I needed the folded towel at one stage, but the rest of the time I felt it wasn't a necessity.
270mm makes for a huge surface area to push down on before slippage at the tip becomes an issue. Any smaller and I would've been toweled up for much more of the vid.
 
As you well know some jobs in a kitchen put more stress on a knife. I prefer to save my hard thin edge blades for the type of prep. that does not stress the edge. Cutting big wheels of cheese chance of slight torque on blade which can damage it.

Why don't you get a less expensive 270mm 57-60 hrt. for the grunt work.

Good luck on your repair. With an expensive blade like that I would dip it in a bucket of H2O every couple passes you do not want that edge to overheat at all on a belt sander. You probably know this, but thought I would mention it anyway.
 
I have a coworker that cut halfway through his left wrist like that. I've never seen so much blood in my life. We bought a two handled dexter cheese knife after that, but he referred to the footlong bullnose that cut him as Lord Voldemort and claimed it made his scar hurt to use it or have it on or near his station.
 
Kippington said:
Yeah I needed the folded towel at one stage, but the rest of the time I felt it wasn't a necessity.
270mm makes for a huge surface area to push down on before slippage at the tip becomes an issue. Any smaller and I would've been toweled up for much more of the vid.
Click to expand...

I meant to ask you earlier... How'd you find the F&F on that knife? Mine was decent but there were some small areas where the mirror polishing could have been a bit better. Also a couple scratches on the blade near the tip on one side just above the bevel which didn't really need to be there, they must have tried sharpening it at the factory with a really low angle. Not too big a deal but something you notice when you pay for a product in that price range.
 
I get queasy when I check this out . Each to his own, but I keep thinking to myself, " I bet I could really til my buddies field up with my Audi convertible if I wanted, but I'm sure his tractor is better suited to the task."
 
Dardeau and marc4pt0, I'm not going to forget that story in a long time. Thanks for the warning, I will consider toweling up more often.

keithsaltydog and chefcomesback, thank you both for reminding me of the importance of proper temperature control during high speed grinding tasks. As you've guessed, I was already aware of this and this won't be the first time I have used the belt grinder to modify one of my ZDP knives, after breaking the tip off one of them.

Which brings me to tjangula's question.

I honestly don't have much experience with knives around this price range so I consider the F&F to be fine for what I use them for. I'm not a picky person, but if I was to really try to find issues with the finish, they would be:

- The ZDP logo on one of them has been stamped in slightly lopsided.
- The shape of the tip isn't the best. I had to regrind the tip of one of mine after it snapped off (I dropped it into the dish-sink while washing it), and I like my work on the tip much better then how they came brand new.
- There seem to be some impurities forged into one of the blades in a couple of places. Even taking the surface metal off the offending area won't remove these marks.

kjs6ylb.jpg

My repaired tip on the left and the factory tip on the right. Notice the impurities in the right blade: they don't scratch off.

I personally have no problems with the mirror polish on either blade, but TBH that kind of thing isn't high up on my list of important features.

Mrmnms said:
I get queasy when I check this out . Each to his own, but I keep thinking to myself, " I bet I could really til my buddies field up with my Audi convertible if I wanted, but I'm sure his tractor is better suited to the task."
Click to expand...

I guess this is the point: To show that these knives are not as brittle or fragile as many people think.
But hey, my next video will be showing how I normally use these knives every day. Just so people don't think that these tests are why I bought these nice knives in the first place.
 
Here we go: A video showing a more 'run of the mill' use with one of these knives.

Shout out to Theory, Salty, CGuarin and everyone else that has done similar videos. I wanted to see how much work was involved in making one and its more then I care to do often, for the time being anyway.

Hope you enjoy.

[video=youtube;HrQYDM4QKK0]https://www.youtube.com/watch?v=HrQYDM4QKK0[/video]
 
Thanks for the kind words guys.

I'll do pumpkin and something frozen in the next couple of days then get started on the repairs.
 
Ok here we go.
There was a birthday drinking session going on in the back during the recording. It's a typical Aussie Sunday night, so apologies in advance for the language. I could've muted the audio but I wanted to keep the sound of the knife hitting stuff in the video.

[video=youtube;Nusg5fxVbuM]https://www.youtube.com/watch?v=Nusg5fxVbuM[/video]

After making pumpkin soup, I was getting pretty drunk and decided to go all medieval on the edge. To you guys that thought the cheese vid was bad, you'll love this one.

[video=youtube;17FPrWiXkf0]https://www.youtube.com/watch?v=17FPrWiXkf0[/video]

Sorry for not doing anything frozen, but there's nothing suitable in the freezer and I'm too lazy to go out and buy anything.
I think I will start repairs today.
 
So in conclusion:
The damage to the edge was only minor throughout the entire experiment.
The pumpkin/squash and the cheese did insignificant damage to the cutting edge. You would need a microscope to see the differences before and after, and the edge retention was great. I honestly think more damage was done hitting the cutting board at the end of each cut, rather then cutting the hard foodstuff. In the pumpkin video I try to put a lot of lateral force into the knife with a lot of twisting at the same time as pulling/pushing on the blade (see 0:54 into the vid and you can hear it). I was hoping for some chip out, similar to what happened in the first post of the thread, but nothing happened.

Thrusting the tip of the knife into a metal lid was surprising - I was prepared for some serious damage but the blade held up fine.

Smacking the knife into the bone did the most damage of all the tests in the form of slight micro chipping and rather surprisingly, minor edge misalignment. I didn't expect an edge hardened to 66-67 HRC to bend just as much as it chipped.
But even then, the damage is so minor that it doesn't really show up on the video, and any of us could repair the edge in one average sharpening session.

Overall I'm very happy with how the edge held up. It's much tougher then I thought, and during the repair I might even thin the blade a bit more then it came OOTB as I think it should be able to handle it. But that's one of the many topics I'll be thinking about during the second half of this thread: Repairs and its effects on edge geometry.
 
This damaged knife seams extraordinary as it is. Have you consider not repair it? Then you’ll get a parmesan and pumpkin proof 67HCR knife. On your video I cannot see any functional problem with the chip. And you’ll save 1.5 to 3 mm ZDP189 and a bunch of time.
 
ZDP might take a high hardness but doesnt it have a lot of toughness for those hardnesses, relatively speaking?

Rockstead's trade show guy does bamboo chopping demonstrations with the stuff though being a pocket knife the thickness is significantly higher. Still, I've always liked ZDP from a pocket knife standpoint; it's just hard to find.
 
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