How sharp is too sharp?

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EricEricEric

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It really depends on the steel itself, some of the knifes may not be able to hold an ultra fine edge for very long if they’re too soft or too brittle, however if the knife is hard enough and durable enough it can hold a much finer usable edge and for a much longer time

That’s the reason we use these special types of knives and why they are so expensive (generally speaking, looking at you vendors who double or more the price)
 

Benuser

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Few strokes. Just enough to make sure the apex meets. On blue steel tosa nakiri.
Sure, but why with such an extremely coarse stone? I know quite some steels benefit from a few strokes on a coarse stone to start the progression with, but have rather 320-500 in mind.
 

M1k3

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Sure, but why with such an extremely coarse stone? I know quite some steels benefit from a few strokes on a coarse stone to start the progression with, but have rather 320-500 in mind.
By accident really. Got interrupted sharpening. Packed it up, went to work. Decided to try it out and was surprised.
 

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i never go below 1k. thats coarse enough imo. its almost like a saw as it is.

well except one time.. i had to cut up some rock wool insulation, and here i found the glass 500 edge to be perfect.
 
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I only read the first page so forgive me if I'm repeating anything said already.

I'll start with this, and I may be getting into semantics a bit, but I still feel it's worth mentioning. A Finer finish does not equate to a sharper blade. If someone is able to manage pressure, keep their stone clean, take very accurate strokes, and deburr well. Then a very fine apex can be achieved at fairly low grits.

On the topic of a finer edge not having bite needed for use in the kitchen. I have a theory that many people accidentally roll their apexes, or round them with either too much pressure on hard finishing stones, or by not keeping a steady angle. A properly sharp blade off of any stone should more or less have a bitey feeling to it. If someone makes a mistake on a finer stone though, it wont impact sharpness as much as on something coarser. So people end up with smoothed over feeling edges. That are more a result of bad sharpening, than going too fine.

With all that said. I just like to go to a mid grit (400 fepa venev resin bonded diamond), and I use 1 micron diamond spray on a strop. It's pretty fine. Has a bit of shine to it, but it's not that crazy.
 

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Yeah I always thought that muddied the waters a lot in these debates. Just imagining the sharpening stone as a field of rocks I can imagine getting significantly finer results from barely skimming the top with a light touch than you would just pushing it in with hard pressure.
 

Kawa

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I only read the first page so forgive me if I'm repeating anything said already.

I'll start with this, and I may be getting into semantics a bit, but I still feel it's worth mentioning. A Finer finish does not equate to a sharper blade. If someone is able to manage pressure, keep their stone clean, take very accurate strokes, and deburr well. Then a very fine apex can be achieved at fairly low grits.

On the topic of a finer edge not having bite needed for use in the kitchen. I have a theory that many people accidentally roll their apexes, or round them with either too much pressure on hard finishing stones, or by not keeping a steady angle. A properly sharp blade off of any stone should more or less have a bitey feeling to it. If someone makes a mistake on a finer stone though, it wont impact sharpness as much as on something coarser. So people end up with smoothed over feeling edges. That are more a result of bad sharpening, than going too fine.

With all that said. I just like to go to a mid grit (400 fepa venev resin bonded diamond), and I use 1 micron diamond spray on a strop. It's pretty fine. Has a bit of shine to it, but it's not that crazy.

Lets be honest. What you are saying here is: when your technique is flawless and you have expert sharpening skills, then a finer stone doesnt give you a sharper edge per se.

For most people for the first years of practising and getting better, generally speaking a higher gritt stone gives you a sharper knive.

It's no use to keep on tyring to get a 800 gritt edge as sharp as a 4000 gritt edge for the first al lot of attempts. Your skills simply arent there to achieve that.

So, yes you are absolutely right.
But in my own experience, since I'm nowhere near expert level, it's way easier to get a screaming sharp knive of a high gritt stone then of a +/- 1000 gritt stone.
I'm sure that counts for a lot of beginners and even semi-advanced sharpeners.
 
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Lets be honest. What you are saying here is: when your technique is flawless and you have expert sharpening skills, then a finer stone doesnt give you a sharper edge per se.

For most people for the first years of practising and getting better, generally speaking a higher gritt stone gives you a sharper knive.

It's no use to keep on tyring to get a 800 gritt edge as sharp as a 4000 gritt edge for the first al lot of attempts. Your skills simply arent there to achieve that.

So, yes you are absolutely right.
But in my own experience, since I'm nowhere near expert level, it's way easier to get a screaming sharp knive of a high gritt stone then of a +/- 1000 gritt stone.
I'm sure that counts for a lot of beginners and even semi-advanced sharpeners
I'm just saying finer doesn't need to equal sharper. Of course it depends on the person sharpening as well.

Also like I brought up in my post. I think the arguements a lot of people bring up for using low to medium grit as the stone they finish on is flawed as well. Because I believe they are likely messing up their edge when going up to the higher grit stones,(by messing up, I mean making mistakes, like using too much pressure or inconsistent angle) because that explains the " smoothed over edge" that a lot of them complain of when polishing to a high grit.

I'm in no way saying what someone should or shouldn't finish their knives on. I'm just pointing out what I've noticed.
 

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The most befuddling aspect of this whole discussion is that everyone's constantly talking about teeth, toothy edge, toothy finish etc, while I have yet to see any high magnification photos of such a thing actually physically existing.
 
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It really depends on the steel itself, some of the knifes may not be able to hold an ultra fine edge for very long if they’re too soft or too brittle, however if the knife is hard enough and durable enough it can hold a much finer usable edge and for a much longer time

That’s the reason we use these special types of knives and why they are so expensive (generally speaking, looking at you vendors who double or more the price)
This is the reason I really advocate for getting some of the steels we don't see too much on kitchen knives to start being used on them. We see people verify that zdp-189, and hap40, do in fact hold edges for a long time on kitchen knives, but for some reason people don't like the idea of using similar western steels, that would likely do even better.

Something like 10v, or maybe s125v or 15v if you want to get really crazy. Heat treated for optimum edge stability. I think will really do amazing holding a fine apex. The hardness, plus the large amount of vanadium cardides together.

I really wish I had the kind of money that would let me support a maker like @Deadboxhero because those guys are really what is going to keep the knife (kitchen or edc) community moving towards better things in the future. In my beliefs.
 
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The most befuddling aspect of this whole discussion is that everyone's constantly talking about teeth, toothy edge, toothy finish etc, while I have yet to see any high magnification photos of such a thing actually physically existing.
Yep. Same lol. I honestly don't even entertain the conversation about that aspect anymore. The "microserrations" I've seen on high magnification photos are basically nonexistent when you get above much rougher stones than anyone except appearatly @M1k3 (lol) finishes on.

I mean I get the bitey description. Because you should feel something biting in when you touch the edge of a sharp knife, but I believe that has nothing to do with their being teeth at the apex.
 

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Then what is it?

I believe it's the apex touching my nail. So what else can I feel than difference in teethsize/height.

Any scratch is a tooth at apex level I think? Even a 100k polished golden ring has scratches when looking in the right light, making it '100k teeth' when you apex that thing?
 

M1k3

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Yep. Same lol. I honestly don't even entertain the conversation about that aspect anymore. The "microserrations" I've seen on high magnification photos are basically nonexistent when you get above much rougher stones than anyone except appearatly @M1k3 (lol) finishes on.

I mean I get the bitey description. Because you should feel something biting in when you touch the edge of a sharp knife, but I believe that has nothing to do with their being teeth at the apex.
Well, the SP 120 is almost to the point of needing refreshing. So it does act a bit finer than it's grit. I forget who it was, but someone passed the HHT challenge off of one.
 
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Then what is it?

I believe it's the apex touching my nail. So what else can I feel than difference in teethsize/height.

Any scratch is a tooth at apex level I think? Even a 100k polished golden ring has scratches when looking in the right light, making it '100k teeth' when you apex that thing?
I think it's most likely the drag felt by the fine apex digging into the material.

Looking at the super high magnification images of edges available. You can see some scratches making it to an apex, and effecting its height, but for the most part it looks almost more random and jagged than the scratch pattern itself. As if the very shape of the very apex is more determined by the way the burr is broken off leaving behind the fine, or not so fine edge at the end.


That's just my guess at the results I see when looking at the images.
 

inferno

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I only read the first page so forgive me if I'm repeating anything said already.

I'll start with this, and I may be getting into semantics a bit, but I still feel it's worth mentioning. A Finer finish does not equate to a sharper blade. If someone is able to manage pressure, keep their stone clean, take very accurate strokes, and deburr well. Then a very fine apex can be achieved at fairly low grits.

from what i have seen on scienceofsharp up to 4k the bevel gets thinner/lower angle, and then after that the apex gets smaller.
so yes finer stones make stuff sharper. not a surprise really. if this was not true there would be no use for fine stones.
people would be shaving off 220ies etc. and this is not happening.
 

inferno

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The most befuddling aspect of this whole discussion is that everyone's constantly talking about teeth, toothy edge, toothy finish etc, while I have yet to see any high magnification photos of such a thing actually physically existing.
here you go sir

 
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here you go sir

The science of sharp photos were the ones I was thinking of when I made my last post. These ones from the article are a good example of exactly what i was mentioning. The peaks and valleys I'm seeing, don't really match up in a way that seems to relate much to the scratch pattern of the abrasive. I mean, you do catch a rare deep scratch that makes an impact on the apex, but not in the whole microserrstion way.

And yes. It is physically easier grind a finer apex with finer abrasives. Especially when someone is using the stones correctly. It still doesn't mean finer abrasive= equals sharper edge/finer apex as a blanket statement.
 
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Been watching this thread with interest.

I agree with @jwthaparc:

I'll start with this, and I may be getting into semantics a bit, but I still feel it's worth mentioning. A Finer finish does not equate to a sharper blade. If someone is able to manage pressure, keep their stone clean, take very accurate strokes, and deburr well. Then a very fine apex can be achieved at fairly low grits.

For colour, I prefer to be a little less eloquent: "you can't polish a turd".

There is no point progressing to the next highest grit until you have finished working on the current grit. If you follow that chain to the beginning... it means the most important work is done at lower grits. It has been a long time since I spent time on razor forums... but from memory they emphasised the importance of 'bevel setting' more than KKF?? I may have that memory wrong. Either way, it is no less true with kitchen knives. You have to do a good job at the low grits, otherwise you are wasting your time at the higher grits!


Well, the SP 120 is almost to the point of needing refreshing. So it does act a bit finer than it's grit. I forget who it was, but someone passed the HHT challenge off of one.

I guess I'll toot my own horn.... that was me.

Ignoring all the caveats about passing the HHT and sharpness, it is a good motivating tool. @captaincaed's challenge (Just Another Dam Project - Pass HHT on your kitchen knife) is an interesting one to take. But it is even more interesting to extend the challenge. Once you are able to pass the HHT... try to do it on the next lowest grit.... and so on... I believe it helps you learn a lot about pressure, angle control and consistency. The pressure aspect was eye opening for me - low grit stones can leave a surprisingly useful edge.

On the SP120... it is a tale of two stones. When fresh it cuts superfast. I love it for thinning. But 10's of seconds later its speed drops off a cliff and it becomes frustratingly slow (compared to its fresh state). The SP120 is a hard stone and does not release grit eagerly. Once glazed the stone does not cut as fast as you would expect from a '120' stone. Although unconventional... with a light touch you could use it for touch ups.



A final note: steel. I dont really consider myself to be a good sharpener. I am not particularly good with soft steels. I also 'cheat' by zeroing out edges with thinning. All that said, I find it easier to get good results with hard steels. Wear resistance is also a good feature. They are more resistant and forgiving of inconsistent angles. I think this makes it is easier to use a 'light touch' by relative standards... the steel can take a little bit of abuse and maintain its edge geometry. Soft steels are more fragile... you need a very, very light touch indeed otherwise you may roll the edge. I think that makes them harder to learn on....
 
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The "microserrations" I've seen on high magnification photos are basically nonexistent when you get above much rougher stones than anyone except appearatly @M1k3 (lol) finishes on.
The peaks and valleys I'm seeing, don't really match up in a way that seems to relate much to the scratch pattern of the abrasive. I mean, you do catch a rare deep scratch that makes an impact on the apex, but not in the whole microserrstion way.

And again... pressure and steel qualities affect this. If you back the pressure off, the abrasive cuts will penetrate the steel less.

In the 120 HHT thread I made the remark:

Even so... the 120 grit is probably around 100-150μm?? Rough for a polish but still relatively small scale!

I think that is consistent with what you are saying. It is a horrible finish (aesthetically).... but is 150μm still very, very small!! It is hard to imagine that affecting a kitchen knife. Again; if you back off the pressure on a glazed stone, I am sure the abrasives will cut even finer than 150μm.
 

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it appears the scratch pattern is only a few % depth of the abrasive particle size.
diamond and SiC seems to plow deeper scratches than alox stones

 

KingShapton

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There is no point progressing to the next highest grit until you have finished working on the current grit. If you follow that chain to the beginning... it means the most important work is done at lower grits. It has been a long time since I spent time on razor forums... but from memory they emphasised the importance of 'bevel setting' more than KKF?? I may have that memory wrong. Either way, it is no less true with kitchen knives. You have to do a good job at the low grits, otherwise you are wasting your time at the higher grits!
Agree completely!


The pressure aspect was eye opening for me - low grit stones can leave a surprisingly useful edge.
Agree completely!

And I agree completely with @jwthaparc
 
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I remember that thread too @Luftmensch I was in the middle of replying to m1ke but I got busy that the fact that it's easy to glaze the 120 over likely made much easier. Not to say it wasn't impressive.

Off topic. I've seen you talk about your 120 glazing quickly when thinning. I highly recommend you increase your pressure. By A LOT especially when thinning. I never had that particular problem with the 120. Once you get enough pressure going for it to release abrasive, you would be surprised how fast the stone eats metal. It could be helped even more if the stone was freshly conditioned with 36 grit sic powder. You honestly don't need to worry about too much pressure when thinning on the shapton 120 in my experience. Short of snapping the stone in half.


Back on topic. Steel 1000% makes sharpening easier. That plus thinness behind the edge. The ideal IMO is a very hard, very wear resistant steel, that is very thin. Short of the edge getting chipped because it was used in the wrong application it get sharper easier, and hold an edge much longer than a softer, thicker counterpart.

Thinness behind the edge makes such a huge difference. I think it is understated. I can argue a super thin maxamet, or 10v knife will sharpen with less effort (with proper abrasives) than a big thick carbon steel knife.
 
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So true....

You can go very far with a 'blunt' knife that is thin behind the edge....
Yeah. I remember seeing a video triple b put out cutting up items with a test blade. It had absolutely no apex, but was so thin behind the edge it was slicing through stuff.


At least I think it was him that put that video out.
 

Kawa

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I consider myself a factual person. I've seen enough arguments to conclude a finer stone doesn't mean a sharper edge (per se?).

But then my own observation..
Why do all of my knives feel and act sharper of a higher gritt stone then of a low or medium gritt stone?

I'm not talking about 'best use in kitchen environment', thats a different discussion.
 
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