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+--- Thread: What is proper sharpness? (/showthread.php?tid=323)
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What is proper sharpness? - SHARPCO - 05-13-2018
I believe that whatever is appropriate is the best.
What about the sharpness of the knife?
DE razor sharp blade is the best?(50 BESS)
What is the most ideal BESS value you think?
Of course, this will depend on which knife is used for what purpose.
RE: What is proper sharpness? - Mark Reich - 05-13-2018
I agree that everything should be sharpened Appropriately. To me that only means one thing- what grit you finish with.
Mr. Grepper's affinity for coarse edges lead me to try to finish on the coarsest Atoma (140 grit), rather than than the 400 grit.
That makes quite a difference in BESS numbers. If I finish on an Atoma alone, 400 grit finishes about BESS 120. Atoma 140 grit finishes about 160.
I don't normally quit there though. Distressing is critical IMHO. I want proven edges, and that usually adds 20-40 points. If I want those points back, it takes very precise dinking around on the Atomas, or just a very small amount of honing on coarse PDP diamond on leather. If I spend more time honing, I can loose aggressiveness and sometimes edge retention (depending on what you're cutting), but significantly lower the BESS score.
Losing aggressiveness isn't all bad, especially at 140 grit. IMHO, that level of coarseness is overkill for a few reasons. First, it's way easier to load the edge with whatever you're cutting. Most fibrous stuff like paper, cardboard, rope, leather and animal tissue and fat can stick to the teeth. Generally, a little stropping on my hand or jeans removes it.
Super coarse edges leave a very rough cut, and have a lot more drag, so ease of slicing is affected. When preparing food, I want much more refinement. A telling exercise is cutting an onion. Coarse edges will make you cry more. Cutting apples, you will see that coarse cuts oxidize (turn brown) faster. Practically all food is like this.
In my experience (virtually always with hard carbon steel), a 140 grit edge will cut more rope. Yes, there's more drag for sure, but very good steel will stay sharper longer. Medium stainless steel isn't strong enough to support very coarse edges, and dulls faster in my experience.
So really, Mr. Sharpco, you answered your own question. BESS sharpness depends on type of steel and usage. I can't say there is something like an optimal sharpness number, but IMHO, most steels at 400-1K grit and BESS 120 to 85 cuts most stuff most easily, and shaves arm hair well, which is the standard most people use most often.
RE: What is proper sharpness? - Bud - 05-13-2018
Very well put Mr. Mark. I think that Thomas speaks to this quite well also. Sharpen for the task at hand. I think we may all be chasing this sharp thing a bit too much. It just makes sense that thin edges will roll more and wear more than thick. If your task doesn't require a thin edge then don't sharpen for one. A 250 edge with tooth will slice the dickens out of a tomato. Wouldn't use it in the morning to shave with though. Too toothy and too dull.
RE: What is proper sharpness? - KnifeGrinders - 05-14-2018
The "proper sharpness" discussion obviously comes from the common observation that thinner edges roll from heavy use.
Firstly, shall we not confuse over-thinned vs properly angled edge with sharpness as such.
Secondly, shall we not confuse toothy vs polished edge with sharpness as such.
Then look at this 'proper sharpness' through Cliff Stamp's "thinnest possible edge for the task" and our experimental data that the best stability to rolling has the lowest possible angle for the steel with the best initial sharpness - and you immediately see that the whole 'proper sharpness' and 'sharpness for the task' concept is untenable.
Sharpness shall always be the best achievable for the given steel sharpened at the acutest angle fitting the task. We do not "sharpen for the task" - we "angle for the task", and angled for the task edge should be sharpened to the sharpest apex you can.
Mike B. has helped me visualize why the sharpest edge is always to the good:
try seeing the rolled edge with your mental vision, see this edge bend and the sharp apex at its end - the stuff it cuts wraps over the bend until it contacts the edge apex where it is severed; when the apex is sharper even the rolled edge cuts with better efficiency. In other words, the sharper edge mitigates edge rolling.
Sharp apex does not predispose the edge to rolling - over-thinning the edge past the angle at which it deforms in cutting certain stuff does.
We could have remembered that a properly sharpened felling axe must shave, to see that the 'proper sharpness' concept is untenable.
"Always check the ax for sharpness... If you followed procedures, your edge should be sharp enough to shave with." Page 31 of the An Ax to Grind. A Practical Ax Manual.
RE: What is proper sharpness? - Mark Reich - 05-17-2018
Mr. KG, I don't understand why you assume Mr. Sharpco's question is about thinning the bevel. I think he would have worded it differently, but maybe I'm the one with the wrong impression.
(Quote, Mr. KG)
"Firstly, shall we not confuse over-thinned vs properly angled edge with sharpness as such.
Secondly, shall we not confuse toothy vs polished edge with sharpness as such. (Unquote)
I'm not sure what constitutes "over-thinned vs properly angled". That's highly subjective, and primarily based on usage. Your experience shows that the difference between "over-thinned" and "properly angled" is only 2 dps, which is astounding.
I'm not sure how to take level of refinement out of the equation. I mean that is probably the most significant quality of an edge. One thing I'm wondering is if coarse edges roll like refined edges.
I recognize Mr. Cliff Stamp's name, but I'm not very familiar with him at all. I understand he can be rather polarizing, but he has a lot of experience. From what little I've seen, he is a proponent of thinning edges pretty dramatically, but he also micro-bevels at a standard 15 dps, so that adds another unqualified variable to the equation. I understand you had no luck with micro-bevels, and my experience is the same.
Of course a common observation about thin primary bevels is that they roll, dent, chip or crinkle relatively easily. It's hard to argue simple physics. The only question is if it will withstand your usage.
If your Normal use is the Maximum that you are willing to use the knife for, it becomes easier to tailor the angle specifically.
A good example is the way you are able to sharpen at 10 dps for inexpensive, medium carbon, stainless, "meat cutting" blades. Meat is extremely soft and totally non-abrasive. In addition, meat cutters are not only experts at carefully using their knives, they also expertly maintain these 10 dps edges constantly.
However, I understand that you can't measure the sharpness of these blades with BESS media at 8 dps, because the test media actually disrupts the edge at that angle. To me, that is both unexpected and very revealing. It's pretty surprising that an edge with maximum performance is only two degrees away from an edge that fails on test media.
Inexpensive meat cutting knives are pretty much opposite expensive, EDC knives. In my experience, less than about 15 dps is too easily damaged, no matter what steel. I've certainly been down this road plenty of times, with lots of different knives.
These are identical blades. They are both Benchmade 710s in M390. The first is very close to the factory edge. It measures 18 dps, with a primary bevel width of < .040".
![[Image: m94HXEI.jpg]](https://i.imgur.com/m94HXEI.jpg)
Here is the exact same blade thinned with an EdgePro to about 8 dps. The width of the primary bevel is now about .20". Approximately 5x as wide.
![[Image: PCa6b1V.jpg]](https://i.imgur.com/PCa6b1V.jpg)
At 8 dps, the edge is very fragile. It takes practically nothing to chip or dent the edge. If I put a .020" dent in the edge, and have to remove... say a .010" thick layer off a bevel that is .20" wide and 3" long. That comes to .006 cubic inches/side.
The 18 dps blade is exponentially harder to chip, which is why it's not a linear equation IMHO, although I would certainly take Mr. Jan's advisement. I'm not sure if I would still have to remove a the same amount off a .040" wide surface 3" long, but that would be .0012 cubic inches/side, which happens to be 5x less. When you're talking hard, wear resistant steel, that means it takes an extraordinary amount of time to sharpen the wide bevel.
The big difference is at 8 dps, M390 is too fragile for typical EDC. It does hold up to BESS media with no damage at all, and it's exceedingly sharp. Actual sharpness was an afterthought, but like any polished EP edge (even regular 20 dps), it passed hair whittling easily.
Like every exotic steel blade I've ever thinned, which is a good pile of knives, by far the biggest affect on these blades is significantly reducing the amount of steel in the blade. It doesn't take long to remove years worth of steel, and I've got all kinds of puny blades to prove it. That is the main reason I just don't thin bevels much anymore.
At 18 dps, M390 cuts practically anything for a long time. I did not hesitate to cut the thick, dirt filled burlap sack holding the root ball of a 12' maple yesterday. I kept cutting the burlap for a minute, seeing if it would get dull. It definitely took the fine edge off, but it kept cutting the burlap very easily. There was no visible damage at all.
I didn't think to measure sharpness before I touched it up. 710 blades are hard to sharpen, with a recurve and long point, but after about 10 minutes on a 1k stone and a few passes on 8µ PDP, it was not consistent, but 79-122. For my purposes that's barely sharp enough for a refined edge, I just didn't want to spend more time on it.
Another fact IMHO is that it's virtually impossible for me to tell much difference between 8 dps and 18 dps in normal use. I'm sorry, but tooth/level of refinement has a much greater affect IMHO. That's something I can actually feel practically every time I cut anything.
My solution is to carry more than one blade, but I end up using a 400 grit, 18 dps blade way more than a 2k grit 10 dps blade by a very wide margin. It is always fun to use a super sharp blade when the need arrises, so I don't mind carrying one.
RE: What is proper sharpness? - Mark Reich - 05-18-2018
Since it seems like it's been a long time since I've seen low numbers on a knife, I decided to see what I could get out of a more refined edge yesterday.
I sharpened a vintage Gerber Balance Plus 4" paring knife on the Kallys. I picked up a pretty complete set when I was Ebaying vintage Gerbers many years ago, and I've always liked them a lot. Balance Plus knives only say "High Carbon Stainless". The only information I've seen is the steel is either 440A or 420HC. I haven't been able to tell much difference among the knives I have, but the steel is very good.
The bevel was set on a Blaze 120 grit with two passes/side. I didn't measure the angle, but a little under 15 dps I reckon. Refined on a Deerfos 800 grit with 2 passes per side, then deburred on a leather belt with 4µ pdp. I need to clean and reload the leather, because it took Way too many passes, like 12-15, to get a clean edge.
I brought the knife in and checked- consistent low 60s. About 10 passes on 1µ PDP on a hone, good. 47-48 all along the edge. Easily hanging hair splitting.
I measured the knife this morning to see how much it lost overnight- back up to 55-60. Shoot. Another 10-12 passes on 1µ PDP- Nice, 43-44.
That's about what I was hoping for. Since I've been spending so much time with coarser edges, it's good to know that more refinement still works, no muss no fuss, for quick low numbers.
The three finger test immediately verified that 1µ PDP is not slick at all, and still shaved my face without harshness.
RE: What is proper sharpness? - Edgepal - 05-21-2018
There is a lot of old traditional knifes out there - and each one of them are designed out of needs and out of use. The fact that one of the oldest knifes we find here in Scandinavia is razors tells that other knifes shall not be as sharp as razors... When a knife become as sharp as a razor - it have become a razor.
City people work in hard dry materials as dry wood, plastic, nylon, cardboard, paper and so on - and they need edges that hold for this type of materials. In the same time, they are romantik and longing for outdoor life, and some days, or weekends, per year, they take their city edged knife and whittle a barberque stick or two, make up fire, baton som firewood - and feel like old trappers that survive for years in Rocky Mountains...
The fact that 90% of humans in the industrial world today lives in citys - and that city knifes have developed edges around 40 degrees to hold for hard dry materials - are not so known... Most City people belive that all knifes hold angles on 40 degrees and that is a normal edge angle on all knifes, world wide.
It is not. Most edges on knifes in the world hold around 18-26 degrees.
In the same time...modern steel are made harder and harder = modern steel is brittle, and today edges chip, before they could role, they never chip. So, to make this hard brittle steel work - edges must be around 40 degrees... That means that they penetrate material badly - compare to edges adound 18-26 degrees.
Traditionals talk about that they wish that their edge shall hold for skin and butcher both a moose and her calf. What can city people meassure their edges with? How many meter cardboard it can cut? How much plastic it can cut?
In my mind, they can only measure sharpness becouse it can not really be meassured by most people - so they slice paper of different kind, they whittle in hair, and ao on - showing how good they can sharpen their edge - in the same time, they have not a clue about how many degrees their edge have...
For me - this tells that the only thing they can perform is that they are good to get the edges two sides to meet properly in a low angle and that they have understand that fine sharpeners gives sharper edges. For me, this is not really sharpening, it is misstreatning a knife = they make all their knifes to razors.
For me, a knife shall only be as sharp it need to be for its purpouse - this becouse that sharpness must allways be balanced against retention. This becouse the edge shall hold as long rime as possible in real use. This becouse of that is the reason to have a functional knife in first place...
Hard words - but I write with a smile and with love.
In Scandinavia we use flat edges in total 18 degrees, singel bevel, for whittling in wet fresh soft wood. If the wood is dry we use higher angle, is it real dry we use a veey thin micro bevel on the cutting edge and try to keep a thin edge so that the edge still penetrate the wood good, ans the micro bevel make that the edge hold for the work.
It can also be balanced with the grit on the last sharpener last in use. Or - balanced by first making a smooth edge - and then make a tothy cutting edge by make teath with a lower grit, or example, sharpen an edge in 10 micron and then make teath with a 30 or 40 micron sharpener with only one passing on the edge in a slightly higher angle.
The three most important things with a edge is: edge angle, edge angle and edge angle. Still - most people have not a clue what edge angle they have on their knifes - and on all forums yiu can read that people write that the angle is not ao important, the important thing is that the knfe works for you...and, of cause, people that sharpen their own knifes are proude of what they have done - and, of cause, the edge they have done work perfect for them.
This is a bad circle. A very bad circle. They can only make the two sides to meet eachother. Nothing more. They do not know in what edge angle. They can not compare two edges with eachother becouse they have different, unknown edge angles. So, what can be learned from not knowing what they just have done to the edge? What can be learn when working with a knife with a unknown edge angle in wood?
The answer is: nothing can be learn. And - they will allways start from scratch everyting they sharpen a knife.
What can be learn when using a knife with a edge angle in total 18 degrees whittling in dry wood? A lot of things can be learned, how a edge in 18 degrees work for just you - and how long this edge holds its sharpness. Then can this edge be sharpened in 20 degrees and you can learn how this edge works for you compared with the edge in 18 degrees - and how much more force you need to use, and how much longer this edge abgle holds for you - and NOW you starts to understand the Basic knowledge of sharpening, different edge angles - and what you have learn now you will allways carry with you for the rest of your life - and you will never more start from scratch again. You will learn new things every time you sharpen your knife with a known new edge angle.
You will also learn how hard different types of wood are, if there is sand in the wood, and so on. After a rather short time you WILL understand what to do to the edge to reach the result you need to have - and you WILL know the result of the change of the edge allready before you have make the change - and for me - THIS is sharpening knowledge.
So, the answer is to understand how edges in different degrees works in different materials - and to use the correct knife with the correct edge angle for the job.
Its alo means that you shall never chop with a knife. If you need to chop, use a axe. Axes are designd for chopping = use your knife to what they are designed for to do.
RE: What is proper sharpness? - Ken S - 05-22-2018
As always, these replies make me think. Thanks to all.
Ken
RE: What is proper sharpness? - Edgepal - 05-23-2018
I have just seen a video where a barber (?) in a barbershop cut womans hair with an axe. He also cut two womans hair with one axe in each hand... He chops the hair of against wood planks.
This video points at some of the things I talk about above. In citys develops new ways off how to absolutley not use edged tools - in traditionals eyes.
We all know that when the axe cutting edge is so sharp that it cuts hair - it do not hold to be chopped down hard in dry wood - it destroy the cutting edge.
I have tryed to copy this video and place IT-chefen dor you to se - but I failed to do that...sorry.
Perhaps this link works... https://www.facebook.com/MetDaanCreative/posts/2303672969863311
Thomas
RE: What is proper sharpness? - KnifeGrinders - 05-23-2018
@Edgepal - yours is such a powerful argumentation, but unfortunately too often all the arguments fall on deaf ears.
I am not talking now of the fellow forumers, but of myself.
Not so long ago I was in the tenants of the same popular fallacies.
But now I am absolutely confident that, no matter what task it is for, the knife benefits from the sharpest edge apex you are able to put on the steel it is made of, while the cutting task determines how much "meat" it needs behind the apex i.e. what the edge angle should be.
The only exception I can think of is skinning a valuable fur with a duller knife as a precaution not to cut it through.