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A thought about burrs

Because this is the kind of nonsense I think about...

To say that when you hone a razor you don't create burrs isn't quite correct. If you have a perfectly set bevel then any further stroke, leading or trailing, on any abrasive stone will create a burr, however small, on the other side. There is a hypothetical scenario in which it is only with the final two strokes on a finishing stone that the bevel finally becomes set, but in practice nobody's actually doing this I don't imagine.

When honing a razor you do create burrs. What you don't do is create noticeable burrs - it's just a matter of perception and definition. And further - the definition of a burr or wire edge probably actually changes depending on what you're cutting with the blade...

---

Last night as an experiment I used a 0.1 pasted balsa strop on an Aogami 2 kitchen knife with a 'zero bevel', which is analogous to the edge of a razor. And I did it in the way you would a razor - using a mixture of strokes including x-strokes and pull strokes to make sure the edge was properly 'de-burred' of any kind of fin or wire edge. And afterwards the very edge felt exactly like that of a razor.

Except it wasn't de-burred, I could tell that by feel. And when I cut something on a board the very edge crumpled, and felt different afterwards. It doesn't really make a difference in use because the wire edge was so fine that it's not strong enough to fold/roll. It just went away - in effect deburring the knife to an extent that the remaining edge - still incredibly sharp - was strong enough to hold up to board work.

When you shave with a straight razor you're using a blade that has what on a kitchen knife I would consider a very small wire edge. Except on a razor it's not a wire edge because you're not cutting things on a board, but try dicing an onion with a 'shave-ready' SR and see if it still is at the end.

---

All of which is only to say that I think talking and thinking about burrs in regards to SRs can be slightly reductive, if done in absolute black-and-white terms. Obviously it is possible to create a wire edge fine and thin enough that a SR won't shave well (I've done that too). But if you really want to understand it, and why it happens, then it's probably better to think about this kind of thing as a spectrum with a significant number variables both internal - to do with the steel, and external - to do with it's application.

---

[NB. Just to state the obvious - wire edges, fin edges, burrs, &c. are all basically the same thing. You just tend to call it a 'burr' when it's thick enough to be noticeably pushed to one side and still cling on.]
 
A razor has what, on a knife, one would consider a wire edge. That is why it is so sharp.

When you look at a razor edge under high magnification it looks perfect after a good honing. After a shave it is beaten to @#$%, and looks like a serrated knife.

Then we strop it, which draws the microscopically bent steel back out into that even "wire" edge, though it is never quite as perfect as it was after the honing.

We repeat that process until the edge is so damaged that the stropping cannot repair the edge enough to deliver a comfy shave, then we hone again.
 
A razor has what, on a knife, one would consider a wire edge. That is why it is so sharp.

Yeah, I'd never really thought about it like this before. Then playing around with a zero bevel knife on a diamond strop last night, made it quite obvious. You could feel the fragility and flex at the very edge with your fingertips, and it didn't paper cut like a knife without a wire edge would have.

(But perhaps what I've said above is all very obvious to most people!)


When you look at a razor edge under high magnification it looks perfect after a good honing. After a shave it is beaten to @#$%, and looks like a serrated knife.

I didn't know this, that's interesting too.
 
I think the issue might be one of terminology.

When I say "wire" edge in this context, I really mean a super fine, fragile edge, not a flaky fin.

I once sharpened a Japanese kitchen knife to the point I could shave my face with it. I basically used razor hones and then pastes to sharpen it until it would shave reasonably comfortably. To be clear, all my kitchen and pocket knives will shave arm hair, but it is another level to shave a beard.

Now, I still dont think that knife had a burr or wire edge, as such. And it was sharp enough to try out some tricky tomato cuts for YouTube, and so on. But the moment that edge hit a cutting board it was not a face shaving edge anymore.

So there is a burr/fin, silly sharp, and practical sharp, and they are all different things.

A burr/fin is no good, it just falls off when touched. A silly sharp edge might be good for cutting whiskers or microscopy specimens, but will fail quickly in the kitchen. That’s your razor. And practical sharp will be robust enough to cut food, or use for chores. It might have micro serrations or “teeth”, and be not so refined, but it will bite into a chicken breast or squishy tomato. The second two have an apex, the first does not.

My recent big epiphany when it came to knife sharpening came when I stopped trying to turn knives into razors, and realised that different edges work better for different tasks, and that there are different types of sharp.
 
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Because this is the kind of nonsense I think about...

To say that when you hone a razor you don't create burrs isn't quite correct. If you have a perfectly set bevel then any further stroke, leading or trailing, on any abrasive stone will create a burr, however small, on the other side. There is a hypothetical scenario in which it is only with the final two strokes on a finishing stone that the bevel finally becomes set, but in practice nobody's actually doing this I don't imagine.

When honing a razor you do create burrs. What you don't do is create noticeable burrs - it's just a matter of perception and definition. And further - the definition of a burr or wire edge probably actually changes depending on what you're cutting with the blade...

---

Last night as an experiment I used a 0.1 pasted balsa strop on an Aogami 2 kitchen knife with a 'zero bevel', which is analogous to the edge of a razor. And I did it in the way you would a razor - using a mixture of strokes including x-strokes and pull strokes to make sure the edge was properly 'de-burred' of any kind of fin or wire edge. And afterwards the very edge felt exactly like that of a razor.

Except it wasn't de-burred, I could tell that by feel. And when I cut something on a board the very edge crumpled, and felt different afterwards. It doesn't really make a difference in use because the wire edge was so fine that it's not strong enough to fold/roll. It just went away - in effect deburring the knife to an extent that the remaining edge - still incredibly sharp - was strong enough to hold up to board work.

When you shave with a straight razor you're using a blade that has what on a kitchen knife I would consider a very small wire edge. Except on a razor it's not a wire edge because you're not cutting things on a board, but try dicing an onion with a 'shave-ready' SR and see if it still is at the end.

---

All of which is only to say that I think talking and thinking about burrs in regards to SRs can be slightly reductive, if done in absolute black-and-white terms. Obviously it is possible to create a wire edge fine and thin enough that a SR won't shave well (I've done that too). But if you really want to understand it, and why it happens, then it's probably better to think about this kind of thing as a spectrum with a significant number variables both internal - to do with the steel, and external - to do with it's application.

---

[NB. Just to state the obvious - wire edges, fin edges, burrs, &c. are all basically the same thing. You just tend to call it a 'burr' when it's thick enough to be noticeably pushed to one side and still cling on.]
I think the hardness of your stones play a big role in the amount of micro burr you end up with. When i sharpen knifes i usually do a combination of push and pull strokes (japanese style) and finish with stropping strokes and maybe some edge leading strokes if i finish on a hard stone.
I think it is a really difficult balance to hit. A soft stone will reduce the amount of burr you end up with, but it will also take out most of the "bite" in your edge. I guess someone with a better technique then my could probably do well on any stones. I prefer what i consider medium hard stones, like the the Shapton glass stones and Naniwa pro.

Recently i got a set of Morihei stones. These are synthetic stones with a mix of natural stone particles. They cut differently then most of my other stones. They are soft (the 9k is hard), but even at a 9k level they leave a little bite in the edge. They also do not create the same burr i get on my Naniwa pro and Shapton stones.
So stone hardness, binder and abrasive particle type also plays a role. Someone with experience just adapts to the stone, but i definitely end up with different results.
 
I think the issue might be one of terminology.

When I say "wire" edge in this context, I really mean a super fine, fragile edge, not a flaky fin.

I once sharpened a Japanese kitchen knife to the point I could shave my face with it. I basically used razor hones and then pastes to sharpen it until it would shave reasonably comfortably. To be clear, all my kitchen and pocket knives will shave arm hair, but it is another level to shave a beard.

Now, I still dont think that knife had a burr or wire edge, as such. And it was sharp enough to try out some tricky tomato cuts for YouTube, and so on. But the moment that edge hit a cutting board it was not a face shaving edge anymore.

So there is a burr/fin, silly sharp, and practical sharp, and they are all different things.

A burr/fin is no good, it just falls off when touched. A silly sharp edge might be good for cutting whiskers or microscopy specimens, but will fail quickly in the kitchen. That’s your razor. And practical sharp will be robust enough to cut food, or use for chores. It might have micro serrations or “teeth”, and be not so refined, but it will bite into a chicken breast or squishy tomato. The second two have an apex, the first does not.

My recent big epiphany when it came to knife sharpening came when I stopped trying to turn knives into razors, and realised that different edges work better for different tasks, and that there are different types of sharp.
Not trying to hijack the thread but your point about knives is spot on. A hair whittling edge is good only if the purpose of the knife is to whittle hair. Sharp enough for the task. And I will say the same about razors. Burs or wires imo are why we strop thoroughly after a honing and this is why imo a razor shaves so much better after the strop.
 
I think the issue might be one of terminology.

When I say "wire" edge in this context, I really mean a super fine, fragile edge, not a flaky fin.

I once sharpened a Japanese kitchen knife to the point I could shave my face with it. I basically used razor hones and then pastes to sharpen it until it would shave reasonably comfortably. To be clear, all my kitchen and pocket knives will shave arm hair, but it is another level to shave a beard.

Now, I still dont think that knife had a burr or wire edge, as such. And it was sharp enough to try out some tricky tomato cuts for YouTube, and so on. But the moment that edge hit a cutting board it was not a face shaving edge anymore.

So there is a burr/fin, silly sharp, and practical sharp, and they are all different things.

A burr/fin is no good, it just falls off when touched. A silly sharp edge might be good for cutting whiskers or microscopy specimens, but will fail quickly in the kitchen. That’s your razor. And practical sharp will be robust enough to cut food, or use for chores. It might have micro serrations or “teeth”, and be not so refined, but it will bite into a chicken breast or squishy tomato. The second two have an apex, the first does not.

My recent big epiphany when it came to knife sharpening came when I stopped trying to turn knives into razors, and realised that different edges work better for different tasks, and that there are different types of sharp.

Indeed... the terminology itself is somewhat blurry, and is probably used in different ways by different people for different things. But that's because the things probably all exist on a spectrum, so trying to draw hard distinctions is difficult or reductive. At what point does the steel at the edge of an apex become so thin or fatigued that it's no longer an edge, but is now a wire edge? And when does a wire edge become a fin edge? It probably depends mostly on its application, and who's got the pencil and drawing the lines.

The knife I balsa stropped last night had what I would call a wire edge. It felt and behaved exactly like a wire edge, though it was so fine it crumbled rather than rolled. It was basically exactly like a razor edge, except on a knife I'd call it a wire edge.

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I think you've sent me your tomato video before, very impressive! It inspired me afterwards to do one of my own, with a slight twist... halving a blueberry by spitting it at a Mazaki. Turns out my spitting aim is quite good! I'll see if I can dig it out...

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You may do this already, and I've probably mentioned before, but if not (and for the benefit of others) - cutting paper is one of the most important tests you can do when sharpening a knife. Not for sharpness - even a relatively blunt knife should cut paper - but the feel of it will tell you an awful lot about the state of the edge with regards to any remaining burr or wire edge. In a way that the thumb nail or three finger tests can't. Do it every time you sharpen any knife blade and it quickly becomes a very useful test. Doesn't matter what kind of paper; newspaper, printer paper, kitchen roll, &c. will all do, it just needs to be the same type every time and you get a feel for how it should be.
 
I think the hardness of your stones play a big role in the amount of micro burr you end up with. When i sharpen knifes i usually do a combination of push and pull strokes (japanese style) and finish with stropping strokes and maybe some edge leading strokes if i finish on a hard stone.
I think it is a really difficult balance to hit. A soft stone will reduce the amount of burr you end up with, but it will also take out most of the "bite" in your edge. I guess someone with a better technique then my could probably do well on any stones. I prefer what i consider medium hard stones, like the the Shapton glass stones and Naniwa pro.

Recently i got a set of Morihei stones. These are synthetic stones with a mix of natural stone particles. They cut differently then most of my other stones. They are soft (the 9k is hard), but even at a 9k level they leave a little bite in the edge. They also do not create the same burr i get on my Naniwa pro and Shapton stones.
So stone hardness, binder and abrasive particle type also plays a role. Someone with experience just adapts to the stone, but i definitely end up with different results.

Yeah certainly easier to deburr on softer stones. Though as you say it can have the potential reduce final bite or sharpness. I guess this is something that plays into what people call 'slurry dulling' in terms of SRs (?). If I'm having real trouble deburring I've started using what on KKF they call the 'Kippington' method, which is basically jointing. I don't think I'd ever do it on a razor, but on a knife it can work quite nicely.

Interesting that you finish with trailing strokes. I always finish leading, though I do tend to finish on quite hard stones - usually novaculites.

I've not used any of the Morihei stones ever, though they sound interesting, and from your description I think might rather like them.
 
Yeah certainly easier to deburr on softer stones. Though as you say it can have the potential reduce final bite or sharpness. I guess this is something that plays into what people call 'slurry dulling' in terms of SRs (?). If I'm having real trouble deburring I've started using what on KKF they call the 'Kippington' method, which is basically jointing. I don't think I'd ever do it on a razor, but on a knife it can work quite nicely.

Interesting that you finish with trailing strokes. I always finish leading, though I do tend to finish on quite hard stones - usually novaculites.

I've not used any of the Morihei stones ever, though they sound interesting, and from your description I think might rather like them.
If i finish on harder stones i deburr edge leading, but on softer stones i have not mastered the skill of deburring edge leading. I might add that i do not own any higher end kitchen knifes with an acute bevel angle. It is probably easier on more acute bevel angles. It also helps if you are working with better steel then i am.
You can actually get some micro convexity on softer stones when you hone SR. I do not use them with slurry, so i guess other factors effect this as well.
These Morihei stones are grate in my my opinion. The 4k and the 9k is really nice. I am not sure about the 1k and the 12k yet. The 1k is not usable for SR in my opinion. I have a Shiro Suita that actually feels quite close to these stones. I Think they have achieved the goal of giving you the feel of a natural stone. They are advertised as being able to give contrast between hard and soft steel. I do not have the knifes to test this. The feedback of these are just something else
 
A razor has what, on a knife, one would consider a wire edge. That is why it is so sharp.

When you look at a razor edge under high magnification it looks perfect after a good honing. After a shave it is beaten to @#$%, and looks like a serrated knife.

Then we strop it, which draws the microscopically bent steel back out into that even "wire" edge, though it is never quite as perfect as it was after the honing.

We repeat that process until the edge is so damaged that the stropping cannot repair the edge enough to deliver a comfy shave, then we hone again.

At what magnification would you expect to see a seriously beaten-up edge after a shave or two?

I know it's not 180x, the top optical setting of my microscope, which, after a shave or two, shows only a few tiny dings. That's of course with my beard, and after I learned to do good prep, and keep the angle low at all times. My edges used to get really beaten up fast when my angle was too high.

What I've seen, using nothing higher than 180x, is that a shave produces little dings; more shaves produce more dings. At some point, you notice the effect on comfort. Or you don't, until there are enough dings that the edge starts catching and tugging on hairs.
 
A few months ago I used the toilet paper cutting test + HHT, to understand the edge state, After removing the "micro chips" or "burr", it will leave a vertex, creating a

new smooth shaving edge, will not cut the toilet paper, reduce the damage to

the skin, pass the edge test of your own habits, and shave smoothly.
 

Steve56

Ask me about shaving naked!
Iwasaki would ‘debur’ the finished edge with CrOx on wool fabric. I don’t really think that‘s what he was doing, but I’ll hold my tongue since there’s only conjecture..

Something that I don’t see discussed is steel quality/characteristics. Some steel makes a burr easily, other steel doesn’t. I have several really old English cast steel razors and they will take a straight, even edge even off a mellow DMT after corrective honing. The same DMT will tear up a Gold Dollar (or Solingen) edge, though you have to do this sometimes to correct geometry. Average SR steel can make a burr fairly easily, it’s more difficult if the steel is hard and fine grained. That said, you can force a burr of some size on anything if that’s your goal.

As far as edge longevity goes, I can get 60+ shaves out of almost any quality razor, and reached 57 on a Japanese Rifuto today, image in the SR forum SOTD. I’m using linen and leather only, no pastes.

Cape 1000 - 63 shaves
Filarmonica Doble Temple - 67 shaves
Filarmonica Sub Cero - 153 shaves
Vintage Thiers Issard 133/134 shaves by Alfredo @Doc226 - there’s a thread on this here that includes my Sub Cero test.
 
A few months ago I used the toilet paper cutting test + HHT, to understand the edge state, After removing the "micro chips" or "burr", it will leave a vertex, creating a

new smooth shaving edge, will not cut the toilet paper, reduce the damage to

the skin, pass the edge test of your own habits, and shave smoothly.

Part of the reason I was thinking about what I said in my original post was that I saw your video and the reaction to it on SRP.

FWIW - I strop a razor less aggressively and with less slack in the strop than you do. But there were certainly (I think) people there who fundamentally misunderstood a valid point that you were making about how an edge will cut, or not cut, different things. And a well honed razor is absolutely about making sure that it won't cut some things well - your skin being the obvious example as you pointed out.

I'll add to this thread later with some more detailed explanation of the physics behind this. But basically yeah - the theory behind your paper test is sound.
 
If i finish on harder stones i deburr edge leading, but on softer stones i have not mastered the skill of deburring edge leading. I might add that i do not own any higher end kitchen knifes with an acute bevel angle. It is probably easier on more acute bevel angles. It also helps if you are working with better steel then i am.
You can actually get some micro convexity on softer stones when you hone SR. I do not use them with slurry, so i guess other factors effect this as well.
These Morihei stones are grate in my my opinion. The 4k and the 9k is really nice. I am not sure about the 1k and the 12k yet. The 1k is not usable for SR in my opinion. I have a Shiro Suita that actually feels quite close to these stones. I Think they have achieved the goal of giving you the feel of a natural stone. They are advertised as being able to give contrast between hard and soft steel. I do not have the knifes to test this. The feedback of these are just something else

You're right - deburring knives with harder steels and lower angle edges is easier. At least in part because you can more easily play around with using microbevels for deburring.

I remember you got a Maruoyama SS :). You definitely need to get a posh Japanese san-mai knife now... those things are extraordinary for bevel polishing!
 
我之所以考慮我在原始帖子中所說的話,部分原因是我在 SRP 上看到了您的視頻以及對它的反應。

FWIW - 我比你更不積極地劃動剃須刀,而且劃動的鬆弛度也比你少。但肯定有(我認為)那裡的人從根本上誤解了你所說的關於邊緣將如何切割或不切割不同事物的有效觀點。一把磨好的剃須刀絕對是為了確保它不會很好地切割一些東西——你的皮膚

稍後我將在此線程中添加一些更詳細的物理解釋。但基本上是的 - 你的紙筆測試背後的理論是合理的。

So I shot this video with the palm of my hand.
 
Because this is the kind of nonsense I think about...

To say that when you hone a razor you don't create burrs isn't quite correct. If you have a perfectly set bevel then any further stroke, leading or trailing, on any abrasive stone will create a burr, however small, on the other side. There is a hypothetical scenario in which it is only with the final two strokes on a finishing stone that the bevel finally becomes set, but in practice nobody's actually doing this I don't imagine.

When honing a razor you do create burrs. What you don't do is create noticeable burrs - it's just a matter of perception and definition. And further - the definition of a burr or wire edge probably actually changes depending on what you're cutting with the blade...

---

Last night as an experiment I used a 0.1 pasted balsa strop on an Aogami 2 kitchen knife with a 'zero bevel', which is analogous to the edge of a razor. And I did it in the way you would a razor - using a mixture of strokes including x-strokes and pull strokes to make sure the edge was properly 'de-burred' of any kind of fin or wire edge. And afterwards the very edge felt exactly like that of a razor.

Except it wasn't de-burred, I could tell that by feel. And when I cut something on a board the very edge crumpled, and felt different afterwards. It doesn't really make a difference in use because the wire edge was so fine that it's not strong enough to fold/roll. It just went away - in effect deburring the knife to an extent that the remaining edge - still incredibly sharp - was strong enough to hold up to board work.

When you shave with a straight razor you're using a blade that has what on a kitchen knife I would consider a very small wire edge. Except on a razor it's not a wire edge because you're not cutting things on a board, but try dicing an onion with a 'shave-ready' SR and see if it still is at the end.

---

All of which is only to say that I think talking and thinking about burrs in regards to SRs can be slightly reductive, if done in absolute black-and-white terms. Obviously it is possible to create a wire edge fine and thin enough that a SR won't shave well (I've done that too). But if you really want to understand it, and why it happens, then it's probably better to think about this kind of thing as a spectrum with a significant number variables both internal - to do with the steel, and external - to do with it's application.

---

[NB. Just to state the obvious - wire edges, fin edges, burrs, &c. are all basically the same thing. You just tend to call it a 'burr' when it's thick enough to be noticeably pushed to one side and still cling on.]
Your brain works like mine does it seems, im on the spectrum, it can be an enormous inconvenience and a pain in the @$$. I've gone down this line of reasoning before and what I could gather is... that's why we strop, everything. I think any type of fin would be pulled off then the remaining teeth straightened when stropping with canvas/firehose/linen/denim/ flesh-side of leather, followed by English bridle/ Latigo/ Hermann Oak and you can get even the most aggressive edges nearly like a very keen coticule. I only strop knives on denim(my jean covered leg) or the Ibrahim of the tail on my belt. Those teeth being straight as opposed to sheered off is far more valuable for knives, especially kitchen/ work knives. I like a fine washita to flesh side of leather for work knives the most.
 
Iwasaki would ‘debur’ the finished edge with CrOx on wool fabric. I don’t really think that‘s what he was doing, but I’ll hold my tongue since there’s only conjecture..

Something that I don’t see discussed is steel quality/characteristics. Some steel makes a burr easily, other steel doesn’t. I have several really old English cast steel razors and they will take a straight, even edge even off a mellow DMT after corrective honing. The same DMT will tear up a Gold Dollar (or Solingen) edge, though you have to do this sometimes to correct geometry. Average SR steel can make a burr fairly easily, it’s more difficult if the steel is hard and fine grained. That said, you can force a burr of some size on anything if that’s your goal.

As far as edge longevity goes, I can get 60+ shaves out of almost any quality razor, and reached 57 on a Japanese Rifuto today, image in the SR forum SOTD. I’m using linen and leather only, no pastes.

Cape 1000 - 63 shaves
Filarmonica Doble Temple - 67 shaves
Filarmonica Sub Cero - 153 shaves
Vintage Thiers Issard 133/134 shaves by Alfredo @Doc226 - there’s a thread on this here that includes my Sub Cero test.

I've read people say before that they can get very good razor edges off DMT, which surprised me to say the least. I would've thought it'd just tear a SR to shreds, as you say.

I don't know so much about the HRC hardness of razor steels. Though I understand that many are at the top end, or higher than, the HTs of Hitatchi steels used in knifemaking for instance...?

I've sharpened a few knives made out of some of these modern 'super-steels' and they can be blindingly difficult to raise burrs on, even with considerable pressure. Especially if using natural stones. Though I guess that if you really know what you're about in terms of razor honing (unlike me!), then that can tie into what you were saying a while back on another thread, about really not needing to use the 'burr method' of bevel setting. Or at least that with very hard steels - that any 'burr' created is just so infinitesimally small that no-one could actually consider it a burr (?)

---

This might interest you Steve... the reason I was buggering about with diamond pasted balsa and knives is that I wanted to see if it'd work on top of a stone finish for kasumi. If I could use it to brighten the hagane, while preserving the haze on the cladding. This was just a couple of minutes polish on BBW, then a couple of minutes on 0.25 then 0.1 pasted balsa strops, but I think has potential.

Before diamond balsa:

IMG-5520.jpg


And after:

IMG-5525.JPG


IMG-5521.jpg


I was pretty impressed with that for a first try tbh! I think something about the give in the balsa means it doesn't start overly polishing or burnishing the soft steel, so maintains the stone finish on that. Also potentially useful for polishing more convexed bevels.
 

Steve56

Ask me about shaving naked!
Not bad! Not all that jigane is the same, even in the same brand. I have a Takeda sasanoa that’s difficult to get a good ji/ha on, and a bunka and a funayuki thats really easy to get good ji/ha.

Mostly it’s the stone though I think.Alex Gilmore said that when he finds a stone that does the slam dunk on the ji/ha, he sets those aside for the knife guys.
 
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