Razor vs toothy edge

B

Bo-dacious

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Hey guys, I have a question about different degrees of sharpness and what they're good for.
Why do different (toothy to razor) edges cut different things better? For example, why does a toothy edge cut meat better than a razor edge.
And what uses does each degree of sharpness have, Ie. Toothy, semi sharp, sharp, shiny, razor.

Thanks for the help, guys,

Bo
 
Cut to about 4.5 minutes in.

There's a lot of geometry involved as well, but in general it has more to do with the mechanical action of the cutting. A lot of along-the-blade favors a coarse edge, pressing the blade directly into a material favors the finer edge.

What is the material, what is the more effective strategy to break it down, what is the desired finish quality of the cut edge?
 
Toothy = increased edge retention and better bite when slicing, reduced edge retention and bite when push-cutting.

Polished = increased edge retention and better bite when push-cutting, reduced edge retention and bite when slicing.

Most edges exist as a weighted balance between those two poles.
 
Shaving is a push cut and some folks like using this type cutting on most items. Rope cutting and skinning use a stroke style cut a pull. Meat cutting is a pull and push stroke. A lot of vegetables are cut with a push and some use a stroke, a pull. Tailor the edge and geometry to the type cutting you'll be doing. DM
 
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Excellent observations. The type of steel is another factor. Many steels that have large(r) carbides (S30V, D2) cut better with a coarse(r) edge (DMT red or even coarse). Some recent super steels (CPM S35Vn, CPM 20CV, CPM S110V, CTS-XHP) seem to have small(er) carbides and will take a finer edge. Plain old high carbon steels with few(er) carbides typically will take a very fine edge (1070/80/95, 50100, 52100).
 
I'll add to this that a "toothy" edge that really grabs material needs to be formed with a very coarse stone. I've seen a lot of people refer to a Spyderco medium edge as "toothy". To me that edge has very little grab. It's more grabby than a very polished edge, but 800 to 900 grit ANSI is *not* toothy to me.

A 320 grit edge (fine India (AlOx) or coarse DMT) has some really nice grab; the coarse DMT in particular is a great balance of sharp and toothy. A 100 micron Norax belt makes a nice toothy edge; very very toothy in fact.

A lot of people don't realize that an edge like the ones above can shave hair *and* be very grabby on the material you are cutting. Once you get to the point that you can make a shaving sharp, clean edge from a coarse stone, things change and you can really start exploring with edge finishes.

Brian.
 
Thank you guys, some more very useful information. And you guys just gave me another thread to start eventually. The types of steels and their carbide configuration. But that's for another day.

Thanks again fellas,

Bo
 
bgentry said:
I'll add to this that a "toothy" edge that really grabs material needs to be formed with a very coarse stone. I've seen a lot of people refer to a Spyderco medium edge as "toothy". To me that edge has very little grab. It's more grabby than a very polished edge, but 800 to 900 grit ANSI is *not* toothy to me.

A 320 grit edge (fine India (AlOx) or coarse DMT) has some really nice grab; the coarse DMT in particular is a great balance of sharp and toothy. A 100 micron Norax belt makes a nice toothy edge; very very toothy in fact.

A lot of people don't realize that an edge like the ones above can shave hair *and* be very grabby on the material you are cutting. Once you get to the point that you can make a shaving sharp, clean edge from a coarse stone, things change and you can really start exploring with edge finishes.

Brian.
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Agree with this above.^

The Spyderco medium (brown/grey) is sort of what I think of as the last, fleeting remnant of 'toothy' in an edge. For a ceramic, it does have some 'bite' that anything slightly more towards 'polished' won't generally have (like the Spyderco Fine). When I use a ceramic to touch up an edge, I almost never go any further than a brown/grey for this reason. I've often thought of the medium as comparing closely to ~ 1200-grit wet/dry sandpaper in finish and bite (depending on the steel type being worked).

But for me, more classic & obvious 'tooth' comes at/below something like ~ 400 or lower, with the Fine India (320 - 360) being a very good example. Lately, I've been finishing many of my knives in simpler steels on this stone, and I like it.
 
Obsessed: so it's ok to give someone a knife finished with a low grit...doesn't have to be a razor right.

Thanks,

Bo
 
Bo-dacious said:
Obsessed: so it's ok to give someone a knife finished with a low grit...doesn't have to be a razor right.

Thanks,

Bo
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Absolutely. If it were mine, I'd more likely prefer it, assuming it's done right, fully apexed & clean. :thumbsup:

A polished 'razor' is impressive, and if done right, shows skill and attention to detail. So, I don't want to downplay that; it's a good exercise in learning how to sharpen and it teaches patience in doing so. But I find a ~ 320-grit edge to be more useful overall for everyday 'normal' knife tasks. That's why I've settled into that ballpark for most everything I sharpen of my own. Not to mention, such edges are much easier to maintain as such, usually one stone and DONE, without worrying about blemishes on high-polished, razor-finished edges. I tried that for a while, when I first got serious about sharpening. But I found it to be a lot more work & fuss than should be necessary for my uses. I also was reluctant to actually use my knives finished that way, considering all the time I spent in making them so polished. That polished hair-whittling 'razor' edge never lasts long anyway, if any real work is done with it. So, one needs to figure out what works for them, and what the right balance is between time & effort expended and usefulness obtained in the results.
 
Obsessed with Edges said:
Absolutely. If it were mine, I'd more likely prefer it, assuming it's done right, fully apexed & clean. :thumbsup:

A polished 'razor' is impressive, and if done right, shows skill and attention to detail. So, I don't want to downplay that; it's a good exercise in learning how to sharpen and it teaches patience in doing so. But I find a ~ 320-grit edge to be more useful overall for everyday 'normal' knife tasks. That's why I've settled into that ballpark for most everything I sharpen of my own. Not to mention, such edges are much easier to maintain as such, usually one stone and DONE, without worrying about blemishes on high-polished, razor-finished edges. I tried that for a while, when I first got serious about sharpening. But I found it to be a lot more work & fuss than should be necessary for my uses. I also was reluctant to actually use my knives finished that way, considering all the time I spent in making them so polished. That polished hair-whittling 'razor' edge never lasts long anyway, if any real work is done with it. So, one needs to figure out what works for them, and what the right balance is between time & effort expended and usefulness obtained in the results.
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Hello David, Interesting Thread and interesting comment. Would you apply the lower grit to all blade steels to include 'Super Steels'? Does it even matter? Thanks.
 
Rhodies said:
Hello David, Interesting Thread and interesting comment. Would you apply the lower grit to all blade steels to include 'Super Steels'? Does it even matter? Thanks.
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According to preference. I've liked something around 325 - 600 for steels like S30V & S90V (DMT 'Coarse' or 'Fine'). With those, that's literally all I need, a single hone and no stropping. And for some of my kitchen knives used with fruits & vegetables, a thin, polished convex works real well; something like ~ 1000 - 2000 or so. I've also liked a polished convex on D2, though I'm still entertaining doing it in something coarser.
 
Obsessed with Edges said:
Absolutely. If it were mine, I'd more likely prefer it, assuming it's done right, fully apexed & clean. :thumbsup:
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That's really the key here. I spent a lot of years thinking that you *had* to have a fairly fine edge (600+ grit) in order to get sharp. The reason I thought this was, I wasn't very good at sharpening! I was not raising a full length burr on both sides and I was not properly removing the burr. Those three words David used above: Fully apex & clean. Those are the keys.

If you take the time to learn how to form a full length burr, make sure it's there, and then cleanly remove it, your edges will go to another level. You'll get REALLY sharp edges even from "coarse" grits like 320.

Sharp and polished are not the same. ...and coarse edges can be really sharp and really useful. :)

Brian.
 
I just got 2 new stones from Konstatnin the owner of Gritomatic to test and they Venev diamond stones that have a new binder that holds everything together and they are both FEPA 1200 or 4000K Japanese grit and they do a really nice job on S110v and M390 those are the steels I have tried them on so far they are still a bit of a toothy edge and they cut everything really well with the edge they leave and they are still shaving sharp.

Bo-dacious said:
Hey guys, I have a question about different degrees of sharpness and what they're good for.
Why do different (toothy to razor) edges cut different things better? For example, why does a toothy edge cut meat better than a razor edge.
And what uses does each degree of sharpness have, Ie. Toothy, semi sharp, sharp, shiny, razor.

Thanks for the help, guys,

Bo
Click to expand...
 
Great info guys! I really thought a polished edge was crucial. Glad to know I don't have to spend that long.

Thanks a lot,

Bo
 
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