What is “Sharp”

[Leo Barr]

The tin is fully open now we will be able to discuss this add infinitum I do think that geometry leads over edge refinement for apparent sharpness if we think of the pure physics of this perhaps one way to prove this would be to take two identical edges of reasonable thickness and sharpen one with a single bevel as far as strops and the other with appropriate thinning and then see how they cut.
One fairly good paper test is to put the knife into an open palm and then draw the paper across the blade without gripping the knife I think this helps to show a truly sharp edge or back to Clay’s edge tester I think the length of material to cut through is relevant since this shows how easily the blade slips through the medium it is cutting where as a thin medium to cut is not so useful for showing the cutting ability of the blade.
Leo Nav

[Leo James Mitchell]

That would be a very interesting test. To define such a test might be difficult but it sure would be something to watch and quantify the results yes?! :woohoo:

Leo

[Gib Curry]

Thanks for the replies. It still confuses me a bit as I sharpen away. Since the whole process is fairly new to me, I’m probably getting better at it without realizing it. I do believe that many of my early sharpening processes were hurried, i.e., not done sufficiently or correctly which may be showing more now that I have some experience, albeit minor, with the WE.

A friend from Portland came to visit last weekend and brought four of her kitchen knives. Two were 8″ Chicago Cutlery chefs. Two were Henckels: one 8″ and one 3″ paring.

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For me, it seems in my current experience, that if I’m not 100% sure I got a burr on both sides at the 400 grit level, then my blades just won’t be what I want them to be.

So, if I’m not sure, I keep stroking/caressing until I am sure. Then, I progress. I’m working to develop the sensitivity to sense the burr at 600. But, as long as I’m sure at 400, then the rest of the progression simply requires me to pay attention and give each side equal care.

For example: the 3″ Henckel paring. The other three blades I got the burr, progressed through the grits and Wow. The paring? There was one little 3/4″ segment that I could never feel a distinct burr. It was kinda, sorta there but not reassuringly definite.

I had left it for last; was hurried a bit so left it that way.

Trying to weave two points together — what my friend hadn’t see was my prior experimentation on her blades.

Fortunately, I had noticed that while the two Chicago Cutlery initially looked identical, they had different “serial” numbers on the blade near the handle. By observation I saw that one had a wider, thinner bevel and one had a narrower, thicker bevel. Didn’t find a lot about it online but it appears the narrower, thicker bevel is for chopping. The wider, thinner bevel for slicing.

My friend also didn’t see that I worked the blade up through the Fine Ceramics and stropped. I am still startled when a blade simply falls through paper — brings a smile to my lips…

But, then I tried to slice a tomato, cucumber and carrot and simply wasn’t happy.

So, I went down to the 800/1000 and “roughed” the edge back up. Then, gave it few strokes each with the Course/Fine ceramics. Good on paper; not my favorite (for these particular blades) on veggies.

Did it again with just the 800/1000 and was happy. Actually did quite well on paper but on those veggies!!!???!!! Cutting tomato & cucumber was like cutting air. Cutting carrot like cutting butter. It still startles me when a blade just falls through a veggie.

And that darn paring knife. Draw the paring knife through paper and it was butter — except that little 3/4″ section I wasn’t sure of.

Now, on the veggies? The paring knife was near perfect. Couldn’t even feel the sticky spot….. (even though I know it is still there.)

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Get the burr…..

One of the real tricks the experts here teach is that you are really tuning the sharpening process to the person, the blade and the task. Putting, at least, those things together and people will be stunned with the edge you give.

(I believe there is, at least, as much Art as there is Science in this sharpening gig.)

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For Now,

Gib

Φ

"Everyday edge for the bevel headed"

"Things work out best for those who make the best out of the way things work out."

[Leo Barr]

My gut feeling is along with you on this a toothy edge is more appropriate for EDC this is I am sure true . I do however feel that geometry is also very important I believe Josh would support this .
I am also unsure as to the need for this with superior steels which I am currently unsure of the real answer for this and hope that eventually we come up with a real irrevocable answer to this.

Leo Nav

[Leo James Mitchell]

Yes Gib I agree…there is a lot of art along with the physics in tuning a blade, as you have discovered. I guess one could write a book titled, Zen and the Art of Sharpening. Using your senses is important.
I keep on using the word ‘caressing’ as you have noted, because to me it says clearly what I should be doing to the edge. I will stop there in my description of caressing so as not to stray into the wrong territory and further embarrass myself! 😆 WHoops! There I go again!

Leo 😉

[Eamon Mc Gowan]

I think in the end, what is sharp, will have to be defined by the end user? When Clay made the sharp edge tester I made one at the same time. We both where running the same test on different edges.
As memory serves me we both came up with a 800 diamond stropped by 14/10 balsa gave the sharpest cut. The problem we found was the test only push cut and the medium to keep it standardized is 3m scotch tape.
Unfortunately the scale does not give real world data? It boiled down to the most “tooth” you can put on the edge is the best push cut.
A 10K chosera edge will not push cut as well as 10um balsa stop. So we are right back to where we started from. You can shave with a 10K chosera, but you can not cut tomatoes, bell peppers, ect. Take the same blade sharpen to 800 diamond, strop with 14/10um and it will cut through the veggies like there not even there!
So the answer in my opinion is the standard answer that Ken Schwartz or Tom Blodgett will tell you “it depends?”
If a list of the best knife sharpeners exist? I think you are going to find Ken Schwartz name in the top ten living knife sharpeners. He has answered with Tom on this forum many a time with ” it depends?”
Maybe we will get lucky and the both of them will see this thread and chime in? I will send PM’s to both and ask that they might add there .02?

[Craig]

All this talk about sharping!!! Time to hit the WE and time to experiment!! Thanks again gentlemen !!

[wickededge]

Great topic, great comments! I think the ultimate definition for sharp begins with edge thickness because effective cutting starts with rupturing the surface of a material. A thinner blade means more concentrated force at the point of contact. There is a physical limit as to how thin an edge can be with steel. I believe it is around .4 microns when the steel has a very fine grain structure. Steels with larger grains cannot reach such a narrow edge thickness. Glass and obsidian can be fractured to much thinner widths. Having micro-teeth is another way to concentrate force at the point of contact such that the knife can still initiate a surface rupture even when it has a larger edge width. Once the surface has been ruptured, other factors like blade geometry come into play. As LeoNav points out, a thick blade with wide shoulders will quickly bog down inside of a cut, creating friction and requiring more force to keep cutting. Thinning and rounding the shoulders helps. I’ve noticed that I can get a knife with a super polished edge to do quite well with tomatoes and such as long as the blade is thin and I’ve sharpened the cutting bevel to a pretty low angle. My thicker blades don’t do as well with a higher polish – they slide right off of zip ties and tomato skins. Thin knives that are highly polished can start a nice cut into a zip tie but don’t have the strength to cut all the way through without significant edge damage.

-Clay

[Leo Barr]

That clarifies some questions one that I am not totally clear on is is a toothy blade more suitable for softer steels like European knives where as harder steels are possible likely to chip ; then also a polished edge on soft steel is possible more likely to roll would I be correct in this assumption?
I read and have refined most of my Japanese chef knives to 3-5K but as Eamon points out a western chef knife will be perceived as wickedly sharp at 600-800 grit.
My best Japanese chef knife an Honyaki Nakira is refined to 16K and slices well .
The deeper we go the more confusing it is .
Then it also struck me is to have a polished bevel with a more toothy bevel so I had a play on some cheap knives and combined a flat bevel asymmetric with a convex more polished bevel the results you can see below I need to play around a bit more and maybe polish the convex side a little more it is polished at the edge since the convex was steeper at the edge and polished that with 5K the other side is 1K

it seems to cut quite well but I have just done it quickly.

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[Eamon Mc Gowan]

Great topic, great comments! I think the ultimate definition for sharp begins with edge thickness because effective cutting starts with rupturing the surface of a material. A thinner blade means more concentrated force at the point of contact. There is a physical limit as to how thin an edge can be with steel. I believe it is around .4 microns when the steel has a very fine grain structure. Steels with larger grains cannot reach such a narrow edge thickness. Glass and obsidian can be fractured to much thinner widths. Having micro-teeth is another way to concentrate force at the point of contact such that the knife can still initiate a surface rupture even when it has a larger edge width. Once the surface has been ruptured, other factors like blade geometry come into play. As LeoNav points out, a thick blade with wide shoulders will quickly bog down inside of a cut, creating friction and requiring more force to keep cutting. Thinning and rounding the shoulders helps. I’ve noticed that I can get a knife with a super polished edge to do quite well with tomatoes and such as long as the blade is thin and I’ve sharpened the cutting bevel to a pretty low angle. My thicker blades don’t do as well with a higher polish – they slide right off of zip ties and tomato skins. Thin knives that are highly polished can start a nice cut into a zip tie but don’t have the strength to cut all the way through without significant edge damage.

Clay, You are the Master!! :woohoo:

[Leo Barr]

I am not a metallurgist and there is an awful lot of technical material to read on the subject; but for instance if I shear a piece of steel would I be correct in the assumption that the bigger the grain- crystalline structure the lower the quality of the steel ?

If this a correct assumption then I see why if the blade on a cheap steel is over refined the edge will soon be lost and a toothy edge with big grains will wear better since the grains breaking away will suit that toothy edge.
A superior steel will support a more refined edge since if pieces brake off the edge they will be so much finer that the edge will endure a not flatten or round as with a cheap knife.

If someone knows more about this I would love to know and I could be wrong in my current understanding perhaps Clay or Anthony could clarify this I am trying to understand the suitable grits for different steels for knives that are used for general purpose in the kitchen or even EDC.
As said in a previous posting I said my forged Honyaki Nakira seems to work well with maximum edge refinement .

[Josh]

Here’s an example of edge geometry from my recent experience. I just thinned down several blades for a home chef… They should perform much better now! It went from around .040″ thick to about .010″. Even though you can’t really see the bevel in the last pic 🙂

Josh

[Gib Curry]

…..It went from around .040″ thick to about .010″. …..

Josh

Very nice.

Just wondering…. do you (and others?) put the micrometer on every blade?

~~~~
For Now,

Gib

Φ

"Everyday edge for the bevel headed"

"Things work out best for those who make the best out of the way things work out."

[Leo Barr]

They should work beautifully for slicing not on crusty bread though they could roll on that .
What make is the western handled Japanese parer ?

[Leo Barr]

I think the important instruments are the mark1 eye ball and the fingers just pinch a blade near the edge to tell what it is good for or whether it needs thinning I imagine Josh has given these measurements to pre-empt the questions that many would like to know.
I firmly believe that it is important to rely on touch and sight as much as possible the more it is used the more useful it becomes I find even with lines or nuts & bolts the more I estimate them the less time is needed and the better the estimation becomes.
Even looking at bevels can be reasonable accurate at least to be able to say if it is
10,15 or a little under 20˚ or under 10˚.
I do of course set bevels on the WE using the Angle cube but it is handy to be able to judge the bevels by sight.

[Author]

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