At What Stone Grit Does a Blade Apex Stop Being Considered Toothy?

000Robert

000Robert

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I wondered about that question a few times and I imagine different people may have different opinions about it. Lately, I have been taking most blades that I want a toothy edge on to 1000 grit. But I wonder at what point would most of you consider an edge apex to be considered polished, as opposed to being toothy.
 
Great question. I have diamond stones in my lansky guided sharpener kit. Also a dmt fine diamond plate to free hand on. Toothy for me is stopping at the medium Lansky stone. Not sure the grit size.

I’m expecting this subject to be interpreted by other to their own standard of toothy. It’ll be interesting to see others perspective.
 
A 1200 (EF) plated diamond hone (think of DMT's EF hone) can still leave a toothy bite in most steels. That has a lot to do with how much harder and deeper-cutting diamond is, relative to the steel's hardness. Diamond cuts much deeper at lighter pressure, relative to it's rated grit size, because it's nearly 10X as hard as hardened cutlery steel and nearly 3X as hard as the hardest of the carbides found in cutlery steels.

Once the relative hardness gap begins to narrow between the abrasive and the steel, even a coarse stone might not cut the steel as deeply and will therefore leave a finer finish than the stone's grit rating would imply. And a worn or glazed coarse stone might not cut it at all. This means it's effect on the steel will tend more towards burnishing/polishing, instead of cutting with aggressive metal removal. And very wear-resistant, carbide-rich steels will limit how much some stones can do. Trying to grind something like D2 on a natural stone, or sometimes even 440C, can be an exercise in frustration, no matter how coarse the natural stone might be. And the carbides in the steel will themselves polish ('glaze') the stone's grit, so the stone becomes even less aggressive as it's used.

Long story short, it depends on the steel, it's hardness and it's carbide content, vs the type of stone and abrasive doing the work.
 
Realysm42 said:
I guess one thing to be mindful of here is the differing ratings between systems. For me 650 / 1100 is where things start to change with Matrix diamond stones.
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Yeah. I use my Wicked Edge 130 and it's diamond stones most of the time. But I have some stones that I can freehand sharpen with on softer steels. They just say course, medium, and fine on them. I found a chart that lists the grit of different stone makers. I'm not sure how accurate that it is.

Sharpening Abrasives chart.png
 
Obsessed with Edges said:
A 1200 (EF) plated diamond hone (think of DMT's EF hone) can still leave a toothy bite in most steels. That has a lot to do with how much harder and deeper-cutting diamond is, relative to the steel's hardness. Diamond cuts much deeper at lighter pressure, relative to it's rated grit size, because it's nearly 10X as hard as hardened cutlery steel and nearly 3X as hard as the hardest of the carbides found in cutlery steels.

Once the relative hardness gap begins to narrow between the abrasive and the steel, even a coarse stone might not cut the steel as deeply and will therefore leave a finer finish than the stone's grit rating would imply. And a worn or glazed coarse stone might not cut it at all. This means it's effect on the steel will tend more towards burnishing/polishing, instead of cutting with aggressive metal removal. And very wear-resistant, carbide-rich steels will limit how much some stones can do. Trying to grind something like D2 on a natural stone, or sometimes even 440C, can be an exercise in frustration, no matter how coarse the natural stone might be. And the carbides in the steel will themselves polish ('glaze') the stone's grit, so the stone becomes even less aggressive as it's used.

Long story short, it depends on the steel, it's hardness and it's carbide content, vs the type of stone and abrasive doing the work.
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My Buck 301 has 425M steel and my Arkansas stones wouldn't even scratch the steel. I had to break out my DMT to sharpen it. Now, I use my Wicked Edge 130 most of the time to sharpen blades.
Maybe what is going to be cut has something to say about what toothiness is? Toothiness to a tomato skin, for instance, may be a courser grit than toothiness would be to my 2" HD Poly strap.
 
To me, the answer is almost entirely subjective:
What is "toothy" to you vs. what is "toothy" to another?
Is it purely visual (mirrored bevel), or is it performance based?
Can anyone adequately describe what a toothy edge is like, visually or functionally, compared to a non-toothy edge?

(If we tried to answer this too objectively, it would depend on our ability to accurately see the apex itself, and under high enough magnification the apex will always be "toothy", and that would never provide an answer to the original question. I recently saw some SEM images of sharpened edges and most were remarkably jagged.)

I apologize if I am over thinking this, it's early, and the coffee is strong....
 
000Robert said:
My Buck 301 has 425M steel and my Arkansas stones wouldn't even scratch the steel. I had to break out my DMT to sharpen it. Now, I use my Wicked Edge 130 most of the time to sharpen blades.
Maybe what is going to be cut has something to say about what toothiness is? Toothiness to a tomato skin, for instance, may be a courser grit than toothiness would be to my 2" HD Poly strap.
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Regarding Buck's 425M steel:

I have an older '4-dot' Buck 112 in 425M. As an example of how it can be left at least somewhat toothy on relatively fine hones, I've usually done my touchups for this blade on a medium Spyderco ceramic (Sharpmaker rods). It leaves just enough 'bite' to immediately grab & hold the edge or the face of a piece of phonebook paper. Also just toothy enough to detect via the '3-finger sticky' test on the fingertips. Anything beyond that medium Spyderco ceramic tends more to a polished finish on that particular blade in that particular steel. I get nearly identical results sharpening 420HC the same way, either in Buck's current blades or in those from Case. And many/most mainstream stainless kitchen knives will finish out the same way, by the same means, as those steels are very similar in makeup to 420HC in general terms. It's also how I maintain most of the kitchen knives I use.

In terms of the finish left by a medium Spyderco ceramic, I've often found it similar to that produced by some NEW 1200-grit SiC sandpaper, used on the same steels as mentioned above. I specify NEW sandpaper, because SiC sandpaper is known to get much finer in finish pretty fast, as the grit breaks down and the paper loads up with swarf. More worn/loaded 1200-grit SiC paper would produce more of a polish and less toothy bite.
 
Obsessed, is the Medium Spyderco ceramic the brown rod in the Sharpmaker kit? Is that what you are referring to?

Thanks. :)
 
karnaknives said:
To me, the answer is almost entirely subjective:
What is "toothy" to you vs. what is "toothy" to another?
Is it purely visual (mirrored bevel), or is it performance based?
Can anyone adequately describe what a toothy edge is like, visually or functionally, compared to a non-toothy edge?

(If we tried to answer this too objectively, it would depend on our ability to accurately see the apex itself, and under high enough magnification the apex will always be "toothy", and that would never provide an answer to the original question. I recently saw some SEM images of sharpened edges and most were remarkably jagged.)

I apologize if I am over thinking this, it's early, and the coffee is strong....
Click to expand...

Under magnification even a highly polished blade will look toothy. I guess the medium that is being cut could have much to say about the toothiness of the blade's edge.
 
I consider an edge 'toothy' if I can either see it (very coarse grind lines) or otherwise feel it - either directly on the skin or via the zipper-like 'buzz' detected when cutting something like paper. And as I mentioned above, I also perceive toothiness in how well an edge will grab, without sliding linearly along the length of the cutting edge, on first contact with material being cut. That's generally the last line of toothiness I perceive, after which anything finer won't have that same 'grab & hold' effect on material being cut. Cutting paper towels or tissue paper is an easy way to see where that line is, for me. Any 'tooth' or bite left in the edge finish will immediately snag & pull fibers from such paper, whereas a really polished finished tends to slide across or through, without pulling those fibers from the paper.

Even a very polished finish on an edge will still look somewhat toothy under high magnification, at the apex. So I don't rely on the visuals too much to see 'tooth' in an edge, unless I'm seeing it by the naked eye at very coarse edge finish, when it can't be ignored.
 
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Toothy depends on context.

I've made and used toothy 400 grit edges on pocketknives used for things like cutting up cardboard. There, toothy means "noticeably raspy, like a little saw." 800 vitrified diamond stone - still toothy. 1K Shapton Glass - not all that toothy.

But for kitchen knives of hard Japanese steel, what toothy means to me is "it will easily slice through tomato skin, and keep doing it even after lots of contact with a cutting board." That kind of toothy edge I can get from some of my JNats (suitas) that top out in the 6000-1000 range (total guess), but which also have enough larger particles to leave some toothy bite.
 
For me toothy is very coarse. Anything above 200 grit is less toothy than I like. The DMT C plate at ~325 still makes toothy edges. But not as toothy as I like them. I have not tried my rolled newspaper cut test on a DMT C sharpened blade, but I suspect it would pass. With a 180 grit belt, blades pass the rolled newspaper test with aplomb. They just mow through it, while polished edges (600 grit belt) almost can't do the job. Almost.

Toothy also grabs skin. When doing the Murray Carter style "three finger sticky" test, a really toothy edge will grab so hard that as you try to move your fingers, the skin remains "stuck" to the blade and you can see the flesh of your fingers staying still on the blade as you *slightly* move your fingers back and forth.

At about 600 grit, I think a blade is no longer noticeably toothy. A blade sharpened on a Spyderco Medium has only a little bit of tooth. On a DMT EF, almost no tooth at all. Both blades would do terribly at the rolled newspaper test.

Just my experiences and opinions.

Brian.
 
Obsessed with Edges said:
I consider an edge 'toothy' if I can either see it (very coarse grind lines) or otherwise feel it - either directly on the skin or via the zipper-like 'buzz' detected when cutting something like paper. And as I mentioned above, I also perceive toothiness in how well an edge will grab, without sliding linearly along the length of the cutting edge, on first contact with material being cut. That's generally the last line of toothiness I perceive, after which anything finer won't have that same 'grab & hold' effect on material being cut. Cutting paper towels or tissue paper is an easy way to see where that line is, for me. Any 'tooth' or bite left in the edge finish will immediately snag & pull fibers from such paper, whereas a really polished finished tends to slide across or through, without pulling those fibers from the paper.

Even a very polished finish on an edge will still look somewhat toothy under high magnification, at the apex. So I don't rely on the visuals too much to see 'tooth' in an edge, unless I'm seeing it by the naked eye at very coarse edge finish, when it can't be ignored.
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What stone grits are you talking about?
 
000Robert said:
What stone grits are you talking about?
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If diamond -> anything up to and including 1200 can be perceptably toothy. Anything beyond that, not as much.

If ceramic -> again, the medium Spyderco is the upper limit of 'toothy' in my perception. As to what its real 'grit' rating might be, that's subjective and varies, depending on whom you ask. As I mentioned earlier, it compares pretty closely to fresh 1200-grit wet/dry SiC sandpaper, in my uses.

But again, a lot depends on what steels you're sharpening and with what abrasive or stone types. Some steels take a toothy bite better than others at a somewhat higher grit, whereas other steels may tend to polish more at the same grit rating. Even blades of one steel type, but at different hardness, can behave differently in this regard. I've noticed this in comparing 420HC from Buck & Case. At somewhat higher hardness, the Buck blade tends to polish a bit more at a given grit, whereas the Case blade retains more 'toothy bite' at the same grit. I noticed this difference in sharpening each on the medium Spyderco, for example. I attribute this to the fine micro-teeth being a little more brittle on the harder blade (the Buck), therefore a little more prone to breaking away and leaving the edge a little more burnished. The micro-teeth on the somewhat less hard Case blade are more ductile and will bend around a bit - but they also tend to hang on a bit longer and can be realigned in touching up the edge, as with a polished kitchen steel.
 
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Grit size is only one of many factors that contribute to toothiness of an edge, and so the question is one that inherently cannot be answered on those grounds alone even if "toothy" were not so subjective a term.
 
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