question about a sharp knife that cant cut tomatoes well

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r0bz

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I sharpened the knife on an 800 gritstone made burr then deburred on it and then moved to 8000 gritstone and deburred on that stone sharpening angle approx 17degrees, the knife is very sharp it cuts through paper with ease but through tomatoes it doesn't work pretty well

what might be the problem?
thank you for all the help
 
What steel is the knife made from? How much time did you spend on the last stone? Do you have problems cutting tomatoes, straight off the 8k stone, even for a short while?
If this is the case I would guess it's a question about either pressure or angle consistency, creating something akin to a ball point pen edge which can still pop hairs and push cut paper, but would struggle with tomato skin, or a lingering small burr/wire edge. I have been very skilled at achieving both these types of edges ;)..
I agree that for longevity it's much better to finish a knife meant for tomatoes on lower grits than 8k, but with good steel it should still do fine for a while.
 
As stated, to really cut tomatoes well, you need a toothier edge than an 8K stone is likely to leave. I don't sharpen anything over 6K anymore, and I only use that for single bevel knives. Chosera 3K + slight stropping is my finisher for every other good steel and they all go through tomatoes on the weight of the blade alone. The only things I really trust for ensuring usable sharpness are tomatoes, peppers and onion skins.
 
Like others have said you need some teeth on your edge. I don't go past 2k on most of my work knives for this reason
 
Garm said:
What steel is the knife made from? How much time did you spend on the last stone? Do you have problems cutting tomatoes, straight off the 8k stone, even for a short while?
If this is the case I would guess it's a question about either pressure or angle consistency, creating something akin to a ball point pen edge which can still pop hairs and push cut paper, but would struggle with tomato skin, or a lingering small burr/wire edge. I have been very skilled at achieving both these types of edges ;)..
I agree that for longevity it's much better to finish a knife meant for tomatoes on lower grits than 8k, but with good steel it should still do fine for a while.
Click to expand...

i spent quite some time at the higher grit stone
 
Garm said:
What steel is the knife made from? How much time did you spend on the last stone? Do you have problems cutting tomatoes, straight off the 8k stone, even for a short while?
If this is the case I would guess it's a question about either pressure or angle consistency, creating something akin to a ball point pen edge which can still pop hairs and push cut paper, but would struggle with tomato skin, or a lingering small burr/wire edge. I have been very skilled at achieving both these types of edges ;)..
I agree that for longevity it's much better to finish a knife meant for tomatoes on lower grits than 8k, but with good steel it should still do fine for a while.
Click to expand...
 
Garm said:
What steel is the knife made from? How much time did you spend on the last stone? Do you have problems cutting tomatoes, straight off the 8k stone, even for a short while?
If this is the case I would guess it's a question about either pressure or angle consistency, creating something akin to a ball point pen edge which can still pop hairs and push cut paper, but would struggle with tomato skin, or a lingering small burr/wire edge. I have been very skilled at achieving both these types of edges ;)..
I agree that for longevity it's much better to finish a knife meant for tomatoes on lower grits than 8k, but with good steel it should still do fine for a while.
Click to expand...
its 58 Rockwell the hardness
 
58rockwell I would say around 1k grit and stropping should give a good bite. Going much further will only loose the bite and beeing softer steel, it won't hold the edge very long so I wouldn't personally go much higher than 1k
 
r0bz said:
its 58 Rockwell the hardness
i spent quite some time at the higher grit stone
Click to expand...
Particularly when you sharpen softer steels higher grit polishes will wash out the teeth on your edge. Try finishing the knife on the king 800>deburring>stropping on the 8k stone. This should clean up your 800grit edge so it doesn't feel terribly coarse, but leave you with tons of bite for veggie prep.
 
for a knife that is around 58HRC a wusthof steel is probably effective but I would not use that steel to hone knives that are much harder than that
 
Alder26 said:
for a knife that is around 58HRC a wusthof steel is probably effective but I would not use that steel to hone knives that are much harder than that
Click to expand...
at what Rockwell level would you say a knife will be harmed from honing it with this honing rod ?
 
With a knife like the one you're describing, I agree with what others have said above.
If 800 and 8k are your only stones I would focus on getting a clean, toothy edge on the 800 and at most use the 8k for a just few very light refining and deburring strokes. Do some test cuts in tomatoes as you progress, and you'll soon dial in on what you prefer, and what the knife can take when it comes to refinement.
For reference, I rarely use an 8k stone, and only with very hard, fine-grained carbon steel.
 
r0bz said:
i spent quite some time at the higher grit stone
Click to expand...
You should have made your knife sharp on your medium (circa 1k) stone. Higher grits are simply to polish the edge, which is done with light pressure and should not take a long time if you have already made a good apex with a coarser stone.

Another way of saying this is that by far most of the work of sharpening is done on the lowest grit stone that you will use.

It's possible that too much work on a fine stone will remove the micro-serrations left by your medium stone. This could account for your tomato problem.
 
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r0bz said:
I sharpened the knife on an 800 gritstone made burr then deburred on it and then moved to 8000 gritstone and deburred on that stone sharpening angle approx 17degrees, the knife is very sharp it cuts through paper with ease but through tomatoes it doesn't work pretty well

what might be the problem?
thank you for all the help
Click to expand...

Aside from all the good responses so far,,,, I'd be willing to bet that your main issue has to do with using too much pressure on your finish strokes, effectively causing the blade's apex to tilt more to one side than the other. You can quickly check if that's the case by verrrrryyyy lightly dragging the pad of your thumb across the blade edge,,,, left to right,,,, then, right to left. If the blade seems to bite a bit more in one direction compared to the other, then that's a sure sign. If that's the case, try stropping the blade VERY LIGHTLY on your finish stone, no more than 1 pull per side at a time. A few strokes should fix the issue, or at the very least, provide an improvement.

Also, check the entire blade length for tilt,,, because.... depending how you stroked the stone, you may find that one portion of the blade tilts to one side for half the length of the blade, and tilts opposite along the remainder of the blade's length.

And,,,,,,,, get yourself a 2k, or 3k or 4k stone. 800 to 8k is too big a jump.
 
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Bobby2shots said:
Aside from all the good responses so far,,,, I'd be willing to bet that your main issue has to do with using too much pressure on your finish strokes, effectively causing the blade's apex to tilt more to one side than the other. You can quickly check if that's the case by verrrrryyyy lightly dragging the pad of your thumb across the blade edge,,,, left to right,,,, then, right to left. If the blade seems to bite a bit more in one direction compared to the other, then that's a sure sign. If that's the case, try stropping the blade VERY LIGHTLY on your finish stone, no more than 1 pull per side at a time. A few strokes should fix the issue, or at the very least, provide an improvement.

Also, check the entire blade length for tilt,,, because.... depending how you stroked the stone, you may find that one portion of the blade tilts to one side for half the length of the blade, and tilts opposite along the remainder of the blade's length.

And,,,,,,,, get yourself a 2k, or 3k or 4k stone. 800 to 8k is too big a jump.
Click to expand...
on the high gritstone i don't apply any pressure other than the weight of the knife only strop like he is doing in this video
 
r0bz said:
on the high gritstone i don't apply any pressure other than the weight of the knife only strop like he is doing in this video
Click to expand...


and,,,,,, what does your thumb test tell you? Same bite in both directions across the entire length of the blade?
 
Simple answer is that it isn’t as sharp as you think it is.
Super polish done well will fall through tomato skins. Look at a couple of Salty’s videos (the OG of the tomato slice vid)





Just leave it at 800grit if it’s working well off that stone.
 
TB_London said:
Simple answer is that it isn’t as sharp as you think it is.
Super polish done well will fall through tomato skins. Look at a couple of Salty’s videos (the OG of the tomato slice vid)





Just leave it at 800grit if it’s working well off that stone.
Click to expand...

it cuts through printer paper like butter and through magazine paper and newspaper like butter ...
i don't know what other tests should be performed
 
r0bz said:
it cuts through printer paper like butter and through magazine paper and newspaper like butter ...
i don't know what other tests should be performed
Click to expand...
You do not need more testing, but what @lemeneid already wrote... tomato skin is a whole different cookie to cut
 
I think it's just god's punishment for using Burrfection video's as a guide... ;)

I do second the question 'what exactly are you sharpening'. If it's German stainless then you're mostly wasting your time. Even if you can create a perfectly polished super fine edge 8000 grit edge it just won't hold it.
 
Jovidah said:
I think it's just god's punishment for using Burrfection video's as a guide... ;)

I do second the question 'what exactly are you sharpening'. If it's German stainless then you're mostly wasting your time. Even if you can create a perfectly polished super fine edge 8000 grit edge it just won't hold it.
Click to expand...
it's German stainless

and also what's wrong with Ricky's video?
i also watched korin knives a long time ago ...
 
The guy is a confusing mix of good advice, bad advice, and just outright incompetent bumbling. He's basically some guy with no prior experiences who watched a bunch of YT channels (the way most of us started), but then decided to immediately launch his own channel and call himself an expert. Most of all he continuously gives me this feeling that he doesn't actually have a clue what he's talking about.
It's hard to take a guy serious who will release a video titled "Blade Thinning - Why You (probably) NEVER need to".... 🤷‍♂️

For German stainless I'd just end on the 800 grit stone... taking that to the 8000 is IMO just a waste of time. Most people around here tend to finish that on 1000-2000 grit at the most.
 
Jovidah said:
The guy is a confusing mix of good advice, bad advice, and just outright incompetent bumbling. He's basically some guy with no prior experiences who watched a bunch of YT channels (the way most of us started), but then decided to immediately launch his own channel and call himself an expert. Most of all he continuously gives me this feeling that he doesn't actually have a clue what he's talking about.
It's hard to take a guy serious who will release a video titled "Blade Thinning - Why You (probably) NEVER need to".... 🤷‍♂️
Click to expand...
who would you suggest to watch as a competent example?
 
There's a bunch of sources that are IMO more to the point, and most importantly, not filled with misinformation.

I learned most from these (in no particular order):
Japanese Knife Imports
https://www.youtube.com/user/JKnifeImports
You'll have to skim through the catalog because not everything is sharpening related.
There's also a wealth of knowledge posted by him throughout these forums over the years, but it might be hard to access that in an efficient manner since it's like little nuggets everywhere.

Korin

You already mentioned you watched this but I figured I'd list this in case anyone else stumbled upon this because it is a good series.

Murray Carter
https://www.youtube.com/c/CarterCutlery/videos
A bit more problematic because from what I can see there's only small tidbits on his YT channel and it's a mess to find what you actually need.

That's probably the most comprehensive. He had an older series that was originally a paid video series. Those were actually really nice but can be a bit hard to find (I have them floating around somewhere). What's interesting is that he does a lot of slightly different thigns, sometimes has some different techniques, and he focuses a lot on fundamental stuff.
I could only track down one of htem on YT (Advanced Blade Sharpening Fundamentals), but there's also one called "Introduction to Knife Sharpening".


These are the 3 that helped me the most starting out. All 3 of these have had professional training and do this essentially for a living (okay Murray is technically a knifemaker, but close enough). This is by no means a final and exclusive list; I'm sure there's other great sources out there.
The biggest problem with Burrfection is that due to him sort of.. figuring out this whole sharpening thing as he went along, and obviously watching some of these videos to teach himself, his videos are a bit of a confusing mess of truths, half-truths and bad advice. Some of it is good, some of it is bad, but for a novice it's very hard to figure out which is which. On top of that he seems to have no knife skills to speak of and all his 'testing' is based on non-valid materials (paper, rope, etc), so he's someone who's only focused on the edge and not on practical cutting performance as a more holistic concept.
 
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