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Angle vs sharpness

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bieniek

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So, its me again with my crazy head. I might again be going after something everybody thinks is BS and crazy, but it makes me wonder so badly...

I mean, the thinking that the knife is sharper with lower angle.

Lets talk edge-wisely strictly.

What I mean is, I started thinking of it, when I could shave face with my ajikiri, which is maybe aorund 40 degrees total, and a yanagi, which would be 15-30 or so.

They are both knives cutting rather soft manner, so Its not about the thickness for me.

Got me thinking, maybe more about precision in sharpening at angle you chosen that the angle itself?
 

GlassEye

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I think precisely sharpening at a less acute angle will be better than poorly sharpening at a more acute angle. We are trying to join two planes, the more precisely this is done, the sharper the edge will be. Now, if you sharpen a 60º edge and 15º edge of same steel with the exact same precision, the 15º is going to cut more easily because it more effectively redirects the force from the material being cut, this would be more evident with denser products. So, the angle one sharpens the edge at will certainly matter for higher performance, but the precision at which that angle is maintained is also important to get the most potential from the chosen angle. Then there is the correlation of durability and angles, but that is another show.
 

bieniek

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jesus dude, 60 degrees... You see whats this forums name?

:D

never managed sharpening kitchen knife at 30 degrees per side, i guess that is out of reasonability?
 

MadMel

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jesus dude, 60 degrees... You see whats this forums name?

:D

never managed sharpening kitchen knife at 30 degrees per side, i guess that is out of reasonability?
hey hey, chef trainers still teach sharpening at a 45 deg angle!!! LOL
 

Citizen Snips

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no they dont, its 45 degrees total. any culinary school teacher will automatically spit out 22.5 degrees and insult the students intelligence by telling them how to come up with that (90 in half is 45 and in half again is 22.5). im not insulting just telling for the sake of my rant.
 

Seth

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Many years ago when I was an artisan type woodworker I read a book by Bruce Hoadley which is apparently still in print:

http://www.amazon.com/dp/1561583588/?tag=skimlinks_replacement-20

He makes exactly this point in his chapters on tool edges. Basically that any rounding due to wobble is dulling an edge not sharpening. If you imagine the tangent line where the two planes meet it is much more obtuse than you would think. IIRC he also said something about not sharpening on anything that has some give or softness as the compression of the, let's say leather, under the edge will create this same effect.
s.
 
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Cadillac J

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Isn't this more of an issue with sharpness versus geometry?

Funny I'm referencing the EP guy Ben Dale on this, but he had a brief video explaining how he can get a machete at 20ish degrees per side to be sharp (as in shave) but it won't cut a carrot or other food products well, while his putty knife has no edge but will fall through a carrot much easier due to how thin it is behind the edge and beyond.

One of the many reasons that shaving with a kitchen knife doesn't mean anything to me--they should all be able to do so--but it doesn't mean they will cut well.
 

hax9215

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I apparently am one of those idiot chef trainers, I teach my students the 22.5 degrees on a side; I believe that this is correct for the stock western knives we issue them. An accurate 22.5 each side is better than most of them will do on their on,plus it is what I was taught thirty years ago by a man named Joe Amendola. I am aware that there is an entire "next level" of knife care in particular with Japanese made high-end cutlery, but if I am incorrect in what I am teaching my students please enlighten me-to learn is to grow.
 

GlassEye

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jesus dude, 60 degrees... You see whats this forums name?

:D

never managed sharpening kitchen knife at 30 degrees per side, i guess that is out of reasonability?
I was just choosing some really wide angle to make my point, I can't think of any application that would require such an edge. Don't worry, my knives all get the most acute edge possible.
 

NO ChoP!

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Mr. Hax, I believe your teachings are spot on for the knives they are probably using. Japanese knives have much harder steal that can hold a more acute edge; simple. Round these parts, it's usually a given we are speaking of said steal, and not German/ French style knives....

I'd bet with thirty years experience, you could teach us all something.....
 

bieniek

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I was just choosing some really wide angle to make my point, I can't think of any application that would require such an edge. Don't worry, my knives all get the most acute edge possible.
Yes, but I meant the difference for a kitchen knife.

One is my yanagi masamoto. I dont really know of the angle but lets say itsno more than 30 degs.
One is the ajikiri I made out of very very cheap blade blank for myself. I wouldve said its no less than 30, propably around its fourties. How thin they are both behind edge, I dont know, but the aji is definitely thicker.
The difference is not a 30 degree, but its there.

Hell, the deba i just got from Jon is way thicker, and get just as sharp.

And what you say of your edges, I dont sharpen on the most obtuse angle I could. I would say its around 15 degrees plus minus 5?
For the sake of the wobble.
But thats why I changed to naturals, I dont want to be a prisoner of any numbers. Not in my hobby.


Cadillac, so what you say? Geometry of the actual edge "point"
 

memorael

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I was thinking about it and sharpening on a smaller angle might provide a better edge. Most people think of edges as being bi-dimensional but if you think of them as three-dimensional then the tip of the edge could form needle like point's which will last less time but cut better. Hard to explain without a drawing but if you have a little imagination you should figure it out.
 

dschonbrun

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I'm very new here, and this is my first post, so I'm hoping you'all will be gentle.

Previous posters have been mainly focused on the secondary bevel angles, but few have discussed the primary bevel. How does the primary bevel impact the overall sharpness and function of the blade?

Thanks,
David
 

Benuser

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The first few milimeters behind the edge are essential; a little thinning behind the edge will boost performance. Any sharpening at a lower angle than that of the very edge will contribute.
 

The hekler

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Going back to the first post, I think you are mistaken in assuming that your whiskers are a relatively soft material on the shave forums I frequent I hear again and again that facial hair is equal to cutting copper wire of the same diameter... Pretty tough stuff in comparison to steak or most veggies... But I agree with your point getting the two sides to meet at an actual edge is much more important then the exact angle in which they do so... Now if only I could only do it with some constancy...
 

Eamon Burke

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Just to the original post...you can shave your face with pretty much anything that has well-aligned pair of bevels that are buffed down considerably and evenly. What's behind the edge barely matters when it comes to cutting hair.

On a kitchen knife, the cutting edge's qualities are just what get you in the door--the rest of the knife does all the work.
 

Benuser

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...were the few mm right behind the edge are essential.
 

bieniek

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Hekler, I wouldnt say that they are soft, and I dont know why I would give that example exactly, but to be fair. Both knives would equally well go thgough bones skin and flesh in sea bass/mountain trout/quail/quinea fowl.

Obviously yanagi has thinner edge and is thinner behind, yet theres no difference in cutting such a substance.

So my question was is angle really most important. And then, how much difference does it make? I mean, How much better can a knife get from changing angle by 3 degrees, if it even is possible? And lets say you would compare two equally thick/thin knives.

And Im saying about the actual sharpness, not the feeling or cutting experience
 

boar_d_laze

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We haven't defined "sharpness" precisely and until we do we're going to have some trouble communicating.

Knives sharpened to more acute angles and at more asymmetric geometries tend to act sharper, everything else being equal. Similarly, knives which are thinner behind the edge also tend to act sharper, everything else being equal.

There's always a tension behind absolute sharpness and durability. More obtuse, more symmetric edges tend to be more durable, everything else being equal.

The best angles and symmetry are often a compromise between absolute or perceived sharpness and durability; but sometimes the best edge rides the edge on one side or another.

In any case, "everything else" is seldom "equal." I wouldn't sharpen my 12" K-Sabatier au carbone (which is only brought out for heavy-duty cutting) to the same angles, geometry or finish level to which sharpen my 300mm Konosuke HD suji, even though they sometimes each end up doing general gyuto stuff.

Both are very frikkin' sharp, thank you very much. But differently sharp. I've rested the big Sab on the end of a chicken wing while paying attention to something else, and gone through the wing without even noticing. That's something the Konosuke, sharpened more acutely, more asymmetrically, and to a higher polish, can't do.

Sharpness is as sharpness does. I don't know about "sharpest," but the best sharpening is fit to the knife and its tasks and it doesn't always involve the most acute angles possible (without instant collapse) or greatest asymmetry (without instant collapse).

BDL
 

bieniek

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Damn, or i cannot write english, or Im considered idiot here. Everything you write about is pretty much natural and reasonable, but it isnt answering my question.

The question was simple.
You have one knife, not a few. It is a kitchen knife, not an axe, razor, meat mincer blade, scissors, coffee grinder blade, whatever else.
And to make it even more precise, it is thick knife. one you use to cut meat,fish. Not vegetables

The level of sharpness you can get out of it, sharpening at your usual angle, is pretty much same every time. Decent. It is a constant. [Cause it seems to me like at my angle I do the same or similar job every time on same knife]

So what happens to your sharpness if you manage to lower the angle by 3 degrees keeping the same stroke consistency? Sharpness of the edge itself. Would you notice change?

I totally understand that lower angle means thinner behind edge, but with meat does that matter all that much?
 

tk59

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Good question. I don't know. I would imagine that it doesn't matter much. I notice it mainly on veggies. I think you should try it and let us know. :)
 

bieniek

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I would like to, but I think you have to have some kind of system to make the effort worth it.

Im not good enough to even tell you approximate of what angle I sharpen at :)

But I thought there would be somebody with the receipt already, I really want to know is there enough pros for changing my routine and angle, which would require crazy lots of effort, isnt it?
Yes, It works for me now, but maybe theres the holy grail there somewhere ??:eek2:
 

bieniek

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Yes, but meditating about sharpening makes me improving my skill. I dont do money on it, nor I want to. But I want to get better than myself from yesterday.

Its the path, i didnt invented it. I guess its about having some kind of target and trying your hardest to get there.

Thats why In almost never happy with my cooking or sharpening.
 

boar_d_laze

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You have one knife, not a few. It is a kitchen knife, not an axe, razor, meat mincer blade, scissors, coffee grinder blade, whatever else.
And to make it even more precise, it is thick knife. one you use to cut meat,fish. Not vegetables

The level of sharpness you can get out of it, sharpening at your usual angle, is pretty much same every time. Decent. It is a constant. [Cause it seems to me like at my angle I do the same or similar job every time on same knife]

So what happens to your sharpness if you manage to lower the angle by 3 degrees keeping the same stroke consistency? Sharpness of the edge itself. Would you notice change?
If the angle isn't very acute to begin with, 3* isn't much; but if it is, 3* is a lot. So...

Is there much difference between 21* and 18*? No. Will you feel it? Probably not.

Is there much difference between 15* and 12*? Yes. Will you feel it? Probably.

As I said, there's always a tension between absolute and perceived sharpness and durability. Whether or not the tighter angles represent more aboslute sharpness is an open question and the answer is probably more definitional than not. At the risk of repeating myself for a third time, making already acute angles still more acute is likely to increase perceived sharpness, but the edge will be more likely to "collapse," and will probably require more steeling if it's a steeling appropriate knife, and more frequent "touch ups" and sharpening if it isn't.

What's the right asymmetry and angle for a given purpose? It depends on the user and the knife. The best way is to find out what works for you and your kit is to keep fooling around until you find something which works for you. The most efficient way to go about it is to start at the most acute angle you think is reasonable, and if it's too acute, sharpen a more obtuse "double bevel" on top of it until you get something appropriate.

There's no single correct answer to your question; and no single best approach to the problem -- other than successive iteration.

Hope this helps,
BDL
 

Benuser

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Im not good enough to even tell you approximate of what angle I sharpen at :)
I think this is the problem. Let me
propose a very simple approach. I hope nobody will be offended by it.
1. Make sure you do know the actual angle at the very edge by measuring it. At which inclination does the edge bite into a board? The actual angle we're looking for is 1 degree lower than we've found.
2. Make sure there isn't a single stroke you make you don't know the angle of. I've made a set of corks with the inclinations which correspond to angles from 5 to 25 degree. The actual value may vary somewhat with the thickness of different knifes, but with a given knife, every stroke becomes repeatable.
3. Verify with the magic marker trick to see where you're abrading exactly.
Don't trust your hand nor eyes. (I wear Varilux glasses, I know what I'm speaking about.)
So you make a bevel a 12 degree, ease the shoulder at 10, thin at 8, make a microbevel at 16. Please write it down. So next time you may do it in exactly the same way - or not. Regards. Bernard
 

SpikeC

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Bernard is right. If you don't know where you are at it does not matter where you go.
 

bieniek

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Thanks to all.

Benuser, Cool if I would have that written down 5 years ago. :D

By saying Im not good enough to judge the angle, I meant I dont care, I just sharpen using my senses, I look, I feel, but I think most importantly I hear where am I.

That is why it is a pleasure. I dont sweat over it.
Please, check the kasumi-hamaguri thread. This might explain it better.

And that is why I said I changed to naturals. There is no numbers. Just you and stone and steel.

But I think its a neverending story. And doesnt matter how well my knife cuts, it could always be better. I want to find better
 
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