How sharp is sharp?

[Ken S]

You are quite correct, Jan, that BESS is based on a (new) double edged razor blade. I see the logic in that. The sharpness of new double edged razor blades is quite consistant, not perfect, not much closer than other sharp edges. The dullness of the broken edge is consistently dull. Again, not quite perfect, but perfect enough. That gives us benchmarks for both sharpness and dullness. To me, that seems an excellent beginning point.

While BESS may not be optimized for kitchen knives, they seem to fall within a useful range. The BESS readings provide useful information, and they are "within tolerance" , to use my favorite old  machinist term.

Ken

[brettgrant99]

You are quite correct, Jan, that BESS is based on a (new) double edged razor blade. I see the logic in that. The sharpness of new double edged razor blades is quite consistant, not perfect, not much closer than other sharp edges. The dullness of the broken edge is consistently dull. Again, not quite perfect, but perfect enough. That gives us benchmarks for both sharpness and dullness. To me, that seems an excellent beginning point.
...

Unfortunately I am not in the stage of life where I wake up at 4 am and am coherent.  I think that perhaps because I am an engineer, this whole discussion irks me.  I am trying to figure out what irks me, and I think it is calling this a standard.  It just doesn't feel like a standard to me.  But how does one say what a standard feels like?  I really don't know what to say, and am bumbling about.  I feel like this is written in an aggressive way, and I don't mean that.

From an overall standpoint, I like the discussion, but the details are what irk me.  When I think about details, I feel like more questions are created than answered.  And then I wonder, does it even really matter?  I think that we all agree that having a way to measure "sharpness" is desired.  And I think that we all agree that a perfect edge just doesn't exist. 

As we observe an edge, it will become less perfect the more that we magnify it.  Where does the magnification end?  At a number that makes sense, like 2x, 10x, 1000x, 1 million magnification?  Or perhaps it is to a scale, 10 nanometers, 10 picometers, or 10 femtometers?  Really those are the same thing, but at some point it becomes difficult to conceptualize how small (or big) something is, so it is human nature to put a comparison on something.  If we could go down to see individual atoms, we would see that steel is really mostly empty space.  Of course at life size, steel is a nice solid, and I think that there is no need to look at it down at the atomic level.

I believe that I had read that sharpening and honing is really the removal of metal grains from the edge.  Does it make sense to magnify down to grain size?  At this point we are talking about procedures and concepts that are not really practical for most of us.  This practicality is one of the reasons that I don't think the conceptual is really very important.  This leads me to think about what is practical?  And I really don't think that a DE razor is really practical for a standard.  I mean sure, they are easy to get, and they seem sharp, but sharp is just a comparison.

Ken mentioned that DE razors are consistent.  What does that even mean?  I shave with a DE safety razor.  I would not consider DE razors to be consistent.  I've used blades made in Russia, Israel, Turkey, India, and Germany.  They all cut different.  DE razor folks consider Feather blades to be the sharpest.  They are made in Japan and I have never used them.  My mother-in-law was scared of knives.  For her, anything sharper than a butter knife was too sharp.  Many people think that a single edge razor is sharp.  Brubacher thinks that a DE razor is sharp.  Go over to some of the shaving forums, and they start to differentiate between brands of DE razors.  Derby's and Crystals aren't as sharp as Mekeur and Feathers.  I haven't even bothered to think about straight razors and how they compare to double edge razors.  How do DE razors compare to scalpels?  What about convex scissors?  Are there other tools that are sharp?  I found an IEEE Abstract for a micro knife that is 500 nanometers thick.  That probably makes a DE razor look like a plate steel.  But again I've fallen into an area of unpracticality.

What then become practical?  I don't think any of us would want to sharpen a DE razor when it is dull.  The sharpest item that I can think of that is sharpened is a straight razor.  Single & Double edge razors are considered disposable.  I suspect that scalpels are no longer sharpened.  Are there knives that may be sharper than DE razors.  Should they be on the scale?  Have they even been tested?

Items that are manufactured are going to fall within tolerances.  Testing enough samples, the results should be gaussian (or normal, or a bell curve).  Has this been proven with DE razors?

Now, let us talk about the other end, the broken end of the DE razor.  How is it broken?  The website says snap.  It then goes on to say that there is no clear apex.  This ignores the mechanisms of fracture mechanics in steel.  From the naked eye, it may appear to be a "clean" break (whatever that means), but upon magnification, how do we know that it is a perpendicular plane and two cutting edges are present.  Perhaps one edge has a smaller area, which would mean higher pressures for the same force, hence it would be "sharper".  I have no proof of this, but neither does the standard disprove this.

What about the test media?  I have never seen it, so these are my guesses.  To me it appears to be a some sort of line, perhaps monofilament?  Perhaps braided?  I don't see a way to measure or ensure a consistent tension in the media.  Perhaps that is part of the spooling mechanism.  A standard would discuss this tension and give generics on its physical properties.

These are just a few thoughts.  This whole process sounds like something another engineer told me once, measure with a micrometer, mark with a crayon.  Ultra precision towards some items and not all items does not lead to precision.

I am pretty sure that the argument used that "sharp as a razor" is in our lexicon is a logical fallacy, as is the appeal that we know what cold is without a thermometer.  To a hydrogen atom, 0C isn't very cold.  But alas, I studied engineering and not philosophic logic, so if they aren't feel free to let me know.

Brett

[Ken S]

Brett,

If we dismiss BESS as a sharpness standard for knife edges, what do we put in its place? While I appreciate the enormous benefits standardization of measurement has brought to all of us, in this case all I really want to do is keep my kitchen knives sharp enough to cut vegetables.

What would be a better term for "standard", given that most standards are not exact?

Ken

[Jan]

Brett, as I have already mentioned, I understand all your reservations. For me the BESS approach is surely not a new universal physical scale of sharpness. Sharpness is a mechanical property of a blade and current physics has sufficient tools and quantities to describe it. The problem is that sharpness is too complex issue.

For me the BESS approach aspires to be a simplified engineering procedure similar to some tests of concrete properties. E.g. the concrete slump test which is an empirical test that measures the consistency of fresh concrete. The test is popular because it is cheap, the procedure is simple and suitable for field conditions. Despite of many simplifying assumptions the slump test is able to guarantee uniformity of concrete from different batches.

My feeling is that the BESS approach is not mature yet. It reminds me the famous Volta and Galvani frog's leg galvanoscope, which was so sensitive that it was used even after the invention of volt and ammeters. 



Jan

[Herman Trivilino]

Promoters of the BESS scale could try, with high-speed photography, to measure the time it takes to break the thread; or whatever it that's cut in the knife test. The product of the force applied and the time of application would give you the impulse, which could and maybe should be measured in newton-seconds. Strictly speaking you'd have to integrate the force with respect to time, which is equivalent to finding the area under the force-time graph. Should be doable with high-speed force sensors, in which case there'd be no need for the photography in the measuring process, but it might be good for marketing promotions.

[Ken S]

Interesting ideas, Herman.

Ken

[Jan]

Herman, I am wondering how you intend to utilize the impulse of force concept to improve the BESS measurements.

During the BESS measurement, the applied force is very slowly increasing, until the pressure at the edge breaks the molecular bonds in the test material and cuts through it. The sharpness in the BESS concept is described by the size of the minimal applied force necessary to cut through the test media. Each BESS unit corresponds to 0.01N (1 centinewton) of applied force.

Jan

[brettgrant99]

Brett,

If we dismiss BESS as a sharpness standard for knife edges, what do we put in its place? While I appreciate the enormous benefits standardization of measurement has brought to all of us, in this case all I really want to do is keep my kitchen knives sharp enough to cut vegetables.

What would be a better term for "standard", given that most standards are not exact?

Ken

I'm not saying that we should dismiss it as a tool, just as a standard.  I'm not really talking about exactness, rather completeness.  Of course, without certifications, standards are really kind of meaningless.

I am actually kind of surprised that a standard doesn't already exist.  My issue is that BESS is at best a tool, and not a standard.  Calling it a standard doesn't make it one.  Even here, others are calling it a procedure or an approach.

Brett

[brettgrant99]

...
For me the BESS approach aspires to be a simplified engineering procedure similar to some tests of concrete properties. E.g. the concrete slump test which is an empirical test that measures the consistency of fresh concrete. The test is popular because it is cheap, the procedure is simple and suitable for field conditions. Despite of many simplifying assumptions the slump test is able to guarantee uniformity of concrete from different batches ...

The concrete slump test is backed by more extensive standards and published by acknowledged standards certification agency, ASTM.  I'm not sure which  agency should own knife sharpness.

Perhaps you all are privy to additional information, but as far as I can tell, bessu.org is owned by Mr. Brubacher, and the only contact info is a gmail account.  This just reinforces in my mind that bessu is a marketing tool for Edge on Up.

I don't have any problem with the testers or the test method.  The owners are allowed to market things the way they want.  The idea isn't bad, it just that it isn't a standard.

Brett

[brettgrant99]

Promoters of the BESS scale could try, with high-speed photography, to measure the time it takes to break the thread; or whatever it that's cut in the knife test. The product of the force applied and the time of application would give you the impulse, which could and maybe should be measured in newton-seconds. Strictly speaking you'd have to integrate the force with respect to time, which is equivalent to finding the area under the force-time graph. Should be doable with high-speed force sensors, in which case there'd be no need for the photography in the measuring process, but it might be good for marketing promotions.

Not bad ideas, but that would make the testers even more expensive.  Perhaps a new thread should be opened up, What I would like to see in a standard, or Less empirical ways to measure sharpness, or Different ways to measure sharpness, or something like that.

I like the discussion.  I think that discussing how to measure these properties is important.  Actually the more that I think about it, perhaps the Edge on Up testers are more akin to the concrete slump test, and different tests would be used to measure whole edge sharpness, edge retention, etc.

Brett.

[wootz]

I love this forum, among others it stands out by its intelligence and constructive criticism.
I have enjoyed Brett's topic on BESS, cleverly formulated, and sobering, and entertaining reading.

Having read Brett's, I re-visited the BESS Universal standard webpage and re-read to stay disillusioned. It is oversimplified to a degree that readers with technical background can't take it seriously. It's not near scientific, nor technical. I am just puzzled why I didn't see it last time, I guess I was reading my expectations, not the actual text.

As to the tool (I use PT50), both thumbs up. A priory I also thought the test media would require controlled tension, but as the media is practically unstretchable by hand, tension control is not needed for the given instrument tolerance.

[Jan]

Brett, I can easy live without the word "standard" attached to the BESS approach.   

Medieval German proverb says "Don't throw the baby out with the bathwater". We should not reject the essential along with the inessential.

Jan

[stevebot]

Today scalpels by and large are not re-sharpened, but they were in my grandfather's day. He learned to sharpen them in medical school and it was he who taught be to sharpen. There is one exception and I had occasion to sharpen one recently. I used only my Tormek, unlike my regular kitchen knife method. Curious, I measured it on a KT20 at 100 on the BESS C scale.  A top notch double edged razor blade measures 50 on this scale, so I have a ways to improve. The scalpel? Let's just say it is used by the rabbi for a certain ceremony.

[Ken S]

A familiar quote of Clausewitz is, "The enemy of a good plan is the dream of a perfect plan." If BESS is not a standard for sharpness, what is the standard?

If there is such a standard, where would one go to test an edge with the laboratory equipment necessary? Perhaps one of the national bureau of standards or one of the top universities?

When a customer asks an honest sharpener if the knife is sharp, does he reply, "I don't really know. We have no way to determine that, as we have no certified sharpness standard . We do have some traditional anecdotal indicators that an edge might appear to be sharp what we carelessly call "sharp"?

Ken

[grepper]

While there is not something like an ISO definition of sharpness, if there is a more or less "standard" I would say that it is this simply due to its longevity:

http://www.catra.org/pages/products/kniveslevel1/st.htm