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Hair vs. tomatoes...

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mateo

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I've been sharpening now for about 2.5 years as a home cook... and I feel my edges are getting better all the time. I can make a very sharp edge, I'm currently hunting for retention (I can make a nice sharp edge, but it's "gone" after 2-4 cutting sessions -- as in noticeably deteriorates, it's still sharp by most people standards).

Beyond that, though, I've been having an issue. My knives can easily shave hair but won't fall through a tomato. No matter what condition they're in -- if I just finished a sharpening session, they won't and if it's been a month or so, they just sit right on top and laugh at me, but they can still shave. What's going on here? Anyone have a bloody clue? It also doesn't matter which knife I'm using.
 

jm2hill

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I'll take a ponder and firstly ask, why knives are you using? I'd imagine if it wasn't thin behind the edge its not going to fall through a tomato!
 

JohnnyChance

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What is your sharpening process? What stone do you finish on? Do you strop, if so, on what? What knives/steels are you using?
 

tk59

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Two things are particularly important here: bevel angles and the alignment of the teeth on your edge. You need low angles and very light stropping and you'll be fine, as long as you're just kissing the edge.
 

Eamon Burke

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Yeah, we need mas informacion. Knives you are using, the sharpening progression and your cutting board.
 

tk59

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I was talking about the tomato part. I forgot the edge retention part. That is more complicated.
 

stevenStefano

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Sounds intriguing. If the blade was slipping off the tomato that would be an easy fix but if it won't cut it well that's different. Perhaps you're sharpening at too high an angle? Guess we won't know until you give a little more info
 

Peco

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Can someone please explain why they need knifes that sharp? I just sharpened my knife using 1000 grit, 5000 grit and raw leather as stropping. Result: a very sharp gyuto that worked extremely well in my kitchen.
 

deanb

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Can someone please explain why they need knifes that sharp? I just sharpened my knife using 1000 grit, 5000 grit and raw leather as stropping. Result: a very sharp gyuto that worked extremely well in my kitchen.
It's the difference between "need" and "want". I want to have knives that sharp. I like to sharpen and the tomato test is a good one.
 

Peco

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It's the difference between "need" and "want". I want to have knives that sharp. I like to sharpen and the tomato test is a good one.
Well you can do the tomato test, slicing thin without gripping it - with a 5K finish + stropping. I just wonder how fragile the edge is when thinning that much? I just received a knife sharpened by Carter, edge were maybe 0,5 milimeter in height and it was razor sharp. Just looking at his edge learned me a lot. After some use I took it to the stones and put a tiny edge on the knife ... became razor sharp again. After some use I used a hone and the edge became toothy which worked well cutting both veggies and protein.

Don't get me wrong, I like my knife sharp too. Sometimes I just wonder why one would go thru tons of grits, diamondsprayed strops etc. when you really don't have to. Of course if it's pure interest or hobby I understand, but for everyday use I can't see why one needs to? Am I wrong saying it's almost overkill?
 

memorael

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To the OP, shaving hair is really not hard at all. I know it sounds like I am exaggerating but the truth is a cinder block and cardboard will take an edge to shaving sharp. If you want to shave to see if it is sharp or not I suggest shaving your beard, anything that pulls, or is painful will pretty much not be "sharp" (take this in perspective to what we are used to around here). Tomatoes on the other hand have a retarded skin that is actually super tough and even more retarded, in my experience, is full grown artichoke skin NOW THAT IS A TEST THERE.

To Peco, you would be amazed at what a ultra sharp knife edge can do in the right hands, forget about brunoise and all that other mambo jambo, I know of someone who's knife was sharpest out of all the ones I have seen (it literally fell through stuff with absolutely no pressure). On the other hand you are thinking well yeah that edge probably lasted one second, and so did I till he was done with all the cutting and the edge was still pristine. Extremely surreal if you ask me, but what was even more surreal was all the cuts he did, they were all perfect, the sides of carrots seemed velvety smooth. So I guess some people do "need" not want an edge that is ultra fine.
 

Peco

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To Peco, you would be amazed at what a ultra sharp knife edge can do in the right hands, forget about brunoise and all that other mambo jambo, I know of someone who's knife was sharpest out of all the ones I have seen (it literally fell through stuff with absolutely no pressure). On the other hand you are thinking well yeah that edge probably lasted one second, and so did I till he was done with all the cutting and the edge was still pristine. Extremely surreal if you ask me, but what was even more surreal was all the cuts he did, they were all perfect, the sides of carrots seemed velvety smooth. So I guess some people do "need" not want an edge that is ultra fine.
That's how I feel when cutting, maybe it's because I made a switch from German knifes :dontknow:
 

tk59

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...Sometimes I just wonder why one would go thru tons of grits, diamondsprayed strops etc. when you really don't have to...
I have some ultrafine compounds. They are useless. I use 1k to resharpen, a min on 5k, a few strokes on 8k and a few strokes on a strop with 1 micron diamond and I can pass all the sharpness tests. I can go months without resharpening if I had to so it isn't that fragile.
 

stevenStefano

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Don't get me wrong, I like my knife sharp too. Sometimes I just wonder why one would go thru tons of grits, diamondsprayed strops etc. when you really don't have to. Of course if it's pure interest or hobby I understand, but for everyday use I can't see why one needs to? Am I wrong saying it's almost overkill?
I think I agree. I know knives and sharpening is a hobby for many people, but I think there is a point of diminishing returns when it comes to sharpening. After I sharpen I spend maybe 5 mins stropping on 0.5 chromium on felt. I don't see the point in going much further than that with incredibly fine compounds, I think the time it takes to use them and notice a difference is better spent doing other things
 

Cadillac J

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I have some ultrafine compounds. They are useless. I use 1k to resharpen, a min on 5k, a few strokes on 8k and a few strokes on a strop with 1 micron diamond and I can pass all the sharpness tests. I can go months without resharpening if I had to so it isn't that fragile.
This. All I use is a 600-1K-5K and usually 1micron strop(or not), and it is all anyone will ever need for double-bevels without any compromise in sharpness/cutting capabilities.
 

mateo

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Sorry guys! Working today...

My usual progression is 1200/8k combo King stone, finish on 0.5 micron diamond on leather strop. I have a Bester 700 that I don't use all the much. Sharpening depends on the knife. My most recent acquisition is a Konosuke Chuka in White #2. This blade I did a rather time consuming multi-stage edge (like single bevel... only I can't think of the word right now) with two different angles on the bevel grind, then a micro-bevel at about 30-35* (I can check this more accurately if needed); for the micro-bevel I went with a visual evaluation on this -- I was recommended that this bevel should be able the width of a hair, so I increased my angle until I hit that width.

Second main knife is my Yoshikane gyuto, SKD tool steel core. This has about a 30/70 (right hand bias -- so 30% is on the left, 70% on the right) blade grind, and what I've found I like is reversing the edge grind to a 70/30; making the bevel much wider on the right side of the knife... which is contrary to the norm, but I find the edge is really nice then... except, of course, on tomatoes. No micro bevel. If I had to guess angles I say left bevel is about 20-25* and the right about 10.

Third is a Takagi nakiri in Blue #2. This knife is hard to sharpen... I haven't honestly been that impressed with my edges. Of all the blade I thought would drop through tomatoes, this one, to me is the most surprising it doesn't. This has about a 40/60 (left/right) bevel grind, with a 15* or so edge bevel. I actually tried to grind the knife like I do the Chuka with a two-stage bevel grind and a very small micro-bevel, but good lord this steel is HARD.

That's what I'm rolling with... I guess what I'm looking for are suggestions here. I know the steel/knives can do it, that's not the question. This is 100% user error... I just am not sure what that error is? Wire edge? Burrs? Not actually forming a proper edge? I'd be happy to post photos, videos, etc.
 

tk59

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I don't get the 70/30 thing. All of my edges have a large bevel on the right side and I'm right handed. Have you tried going without the leather strop? What happens to your edge retention then? When you notice your edge isn't cutting great, can you see light reflecting off the edge when it's pointed right at you?

As for the tomato thing, 25 deg is WAY too big. Go to 15 deg. It isn't wire edge/burr either because one can pass the tomato test with a wire edge, no problem.
 

allumirati

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1st thing is to find the right angle for the knife. Usually I'll try to go as thin as I can go, then I have problems with it, then I put a micro-bevel that is to high and becomes to big over time so it's very sharp but not scary sharp. So then next step is to go a step down from there. Which is medium angle usually about 15* per side. I also like asymetric sharpening but that gets a bit more complicated for me (if I'm trying to make a DURABLE edge). I like to play with different angles a lot at this point and I'm always changing my methods but medium angles are a good place to start.

2nd thing. I know this is contrary to instinct and to 99.9% others' advice but...use as much pressure as possible. This will ensure you're removing the weak metal and actually sharpening the metal you're going to be cutting with, not the metal you're going to be removing later.

3rd thing either don't polish too much (more than 4k-6k) or get a natural stone which most of the time give you highly polished but "bitey" edges.

4th thing if doing a symetrical grind you can count down (alternating sides) strokes for instance I use 3,2,1, 1/2. 1/2 meaning only grinding from heel to tip or tip to heel, 1 meaning both ways. If you do single strokes you can start with a higher number. Of course that takes more time then which some of us don't have much. Obviously if you want asymetrical you can switch numbers like 6-4, 7-3, etc. Basically you want to make sure you're using each stone to it's full potential by making sure you're refining the edge to it's max on that particular stone.

Good luck :p
 

allumirati

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Forgot another thing...if you want to thin the edge try not to go all the way to the edge when sharpening at extremely low angles otherwise you'll weaken the edge. I know it's tempting to get the lowest possible angle on a knife. But an ultra acute edge that's rolled is way worse than a crisp medium angled edge.
 

memorael

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Its sexy isn't it when the carrot doesn't bleed and the mouth feel is all crunchy and velvety.
 

bikehunter

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..... and even more retarded, in my experience, is full grown artichoke skin NOW THAT IS A TEST THERE.
In my experience, prepping artichokes is very close to the ultimate, edge holding stress test for any kitchen knife. <G>
 

heirkb

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...When you notice your edge isn't cutting great, can you see light reflecting off the edge when it's pointed right at you?...
What would it mean if one were to see this? That one has a wire edge that has rolled? I've seen this on segments of my edges before, but I'm pretty sure that was because of me stupidly banging the edge on something.
 

tk59

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...use as much pressure as possible. This will ensure you're removing the weak metal and actually sharpening the metal you're going to be cutting with, not the metal you're going to be removing later...
The only thing tons of pressure assures you of is making a more concave edge. If that's what you want, fine. In smaller bevels and thinner blade geometries, the edge will be weaker but thinner very close to the edge and thickening up dramatically as you reach the shoulder on your bevel. If you go lighter, you can drop your angle and get the same edge strength. If you want to be assured you are removing all the weak metal, you just need to make sure you have a significant burr at some point OR you can make a microbevel OR you can do a 90 deg deburr, etc. That part has absolutely nothing at all to do with pressure.
 

tk59

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What would it mean if one were to see this? That one has a wire edge that has rolled? I've seen this on segments of my edges before, but I'm pretty sure that was because of me stupidly banging the edge on something.
Some people say they can get through a complete shift on a wire edge. To me that's really just a thin, weak edge. To me, a wire edge is one that folds over after one tomato slice or so. If substantial parts of the edge have rolled over after one slice, it's a wire edge. If it takes a lot of slices then maybe the edge is just a bit thin and I would have recommended thickening up or decreasing pressure or putting a micro on, etc.
 

heirkb

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Thanks for the response. I guess it was me accidentally banging the edge, then.
 

allumirati

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The only thing tons of pressure assures you of is making a more concave edge. If that's what you want, fine. In smaller bevels and thinner blade geometries, the edge will be weaker but thinner very close to the edge and thickening up dramatically as you reach the shoulder on your bevel. If you go lighter, you can drop your angle and get the same edge strength. If you want to be assured you are removing all the weak metal, you just need to make sure you have a significant burr at some point OR you can make a microbevel OR you can do a 90 deg deburr, etc. That part has absolutely nothing at all to do with pressure.

I knew nobody was going to agree with me on this, but take it for what you will. I just know that when I sharpen this way my edges last longer and I put them through a lot 6 days a week and I don't have to hit anything below 8 or 4k a day for a week. And when I do I don't really have to I just like thinning. Anyways it's not about getting rid of the metal that you can see coming off, it's about removing the metal that you used to make thousands of cuts during the week so it makes clean hundreds of cuts a night and almost everything I cut is tougher than tomatoes. And the whole thing about bringing a burr on each stone makes sense in theory, but in practice if you don't use enough pressure you're only flipping the burr that was created by the first stone rather than pushing it off into the stone so the stone can go to work on the edge below that. So your left with a nice shiny uber sharp wire edge. And no amount of "deburring" after this point is going to leave you with as clean an edge as you could have.
 

memorael

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I knew nobody was going to agree with me on this, but take it for what you will. I just know that when I sharpen this way my edges last longer and I put them through a lot 6 days a week and I don't have to hit anything below 8 or 4k a day for a week. And when I do I don't really have to I just like thinning. Anyways it's not about getting rid of the metal that you can see coming off, it's about removing the metal that you used to make thousands of cuts during the week so it makes clean hundreds of cuts a night and almost everything I cut is tougher than tomatoes. And the whole thing about bringing a burr on each stone makes sense in theory, but in practice if you don't use enough pressure you're only flipping the burr that was created by the first stone rather than pushing it off into the stone so the stone can go to work on the edge below that. So your left with a nice shiny uber sharp wire edge. And no amount of "deburring" after this point is going to leave you with as clean an edge as you could have.
This is completely false. Saying you put a lot of pressure doesn't really mean anything concrete. Anyway if you put a LOT of pressure you will create mini grantons on a very small scale on every finger that you put pressure on. This will create a weak edge and at the end of the day all you get is a week edge. Also 4k and 8k are two very different stones so I get a bit confused on this too. If you get over a whole week with little to no work on your knife kudos, I am just sure it isn't because of your explanation, something else is at work there.
 

Cadillac J

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I do agree that you have to make sure you removed all the fatigued metal in order to have edge longevity, but you don't need extreme pressure to do this...just have to make sure you spend a bit more time grinding after you first feel the burr form.

Everyone here that is a good sharpener has their own way of doing things--we might not all agree with each other on specifics, but if you are getting results that make you happy, good for you.
 
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