How sharp is sharp?

[Jan]

Recently I read the definition of the BESS scale and BESS unit and I got the impression that there is a need to improve the purity of physical terminology. 

http://www.bessu.org/ states: "The BESS scale ranges from 0 to 2000 units. Each unit represents one gram of pressure. BESS certified test media requires 50 grams of pressure to sever when measuring the edge of a DE blade, so with the BESS and when measuring DE blades, 50 grams of pressure is the BESS "0" point. "

Gram is SI derived unit of mass (g).
Pressure is given by a force per unit area, SI unit of pressure is pascal (Pa).
Caution is needed when we want to compare or relate different physical quantities.

In physical terminology the test media is exposed to a pressure given by concentration of the applied force onto the small edge area. The size of the applied force is described by the weight of some mass (50 to 2000 g).

Jan

P.S.: Assuming the gravity acceleration is 10 m/s², than the BESS scale ranges from 0 to 20 N and each BESS unit corresponds to 0.01N (1 centinewton) of applied force. 

[brettgrant99]

I first read about BESS, maybe three days ago.  I am still trying to process it, but to me it is more marketing trying to sell itself as a standard, then a standard.  There is no information about the BESSU organization that I can find.  Perhaps I am missing something.

Perhaps something to be discussed in a new thread.  I'll mull it over some more.

[Ken S]

I believe we are making this overly complicated. Water freezes at a certain temperature and boils at another. Whether we call it celsius or Fahrenheit, it is the same temperature. In the case of knife edge sharpness, a certain amount of pressure on a knife is required  to break a test media. BESS uses a scale of weight on the edge. Fifty grams will cause a new double edge razor blade to cut through the test media. Two thousand grams will break the test media with the broken edge of the razor blade.

A new knife with a reading of three hundred grams has become keener after sharpening if the new BESS reading is two hundred grams. If, after much use, the edge reads six hundred grams BESS, the edge needs sharpening.

Granted, this reading reflects the spot on the edge where the reading is made. This accuracy can be increased with readings at several locations on the edge. How much accuracy do we really need? If we insist on readings for the entire blade edge and throughout the entire process of use, we will require laboratory equipment of considerably more cost and size.

Yes, BESS is not a universally accepted standard like Fahrenheit. However, at one time, Fahrenheit was just a newly conceived idea for measuring temperature. How fortunate we are to be living at the time when BESS is in its first days. Someday we will regale our grandchildren with tales of the early days of BESS!

Ken

Ken

[wootz]

I first read about BESS, maybe three days ago.  I am still trying to process it, but to me it is more marketing trying to sell itself as a standard, then a standard.  There is no information about the BESSU organization that I can find.  Perhaps I am missing something.

Perhaps something to be discussed in a new thread.  I'll mull it over some more.

Well, you can equally say that wireless standard is no more than marketing to sell mobile phones internationally.

BESS was first published in 2014, we are witnessing an attempt to introduce a global standard at its early stage.
It is independent of sharpness tester make.
The idea is that readings of different brands could be translated into a globally accepted unit of measurement, as a means of communicating sharpness values in an unambiguous manner.

I learned more about BESS from discussion with one of the board members here:
http://www.bladeforums.com/forums/showthread.php/1282984-Knife-Sharpness-Scale

And Jan is absolutely right, when you introduce a new standard scale, terminology must be accurate, you can't substitute weight to pressure, even if grams is the only reading you need to tell about the pressure.
Jan's remark is so to the point that if came to my mind, I'd write to Mike.

Mike Brubacher has funds, resources and passion, and it won't take him long to popularize the BESS standard over the globe.
I feel pretty much like Ken said, "How fortunate we are to be living at the time when BESS is in its first days."
Even discussing it here gives me a silly but happy feeling of being a part of the history making.

[Ken S]

Wootz,

I read your link after submitting my last post. I was unaware of the bladeforum reference to water temperature. I think it is a good reference, just not original with me.

Ken

[wootz]

Dear Ken, Mendeleev wasn't first to notice elements periodicity, but who cares about those first?

[Ken S]

Good point, Wootz. I learned something. I am embarressed to admit that neither my high school or college science included any chemistry. In hindsight, not a wise decision. I googled Mendeleev. I must learn more about him. My online personal study has been mostly ancient history recently. I have much to learn.

I think it is important not to overlook a basic function of edge testing. The paper test method can be very subjective. The edgeonup HT-50 provides the new Tormek user with a simple means to consistently determine if his edges are sharp. The BESS readings can be compared with the before sharpening readings, whether with a new knife of a veteran kitchen knife.  This easily solves one of the frustrating mysteries of sharpening, how sharp are my edges? This giant step places the new or not so new sharpener much closer to mastering the craft.

If these BESS readings are recorded, the sharpener can note his progress over time. That's a great confidence builder.

Ken

[Jan]

I have sent a copy of my post also to Mike B. He answered promptly, thanked for the suggestions and promised to forward it to Bernie at BEESU. Mike mentioned that BESSU's web probably reflects the simplistic approach, while now they are pushed to express the BESS in more specific and generally accepted engineering terms. 

I understand all the reservation expressed by Brett and Magnus. Edge sharpness is very complex issue and the BESS approach addresses only some aspects of it, however it seems to be cheap and repeatable. My intention was to help them to describe it aptly and physically correctly. 

Wootz, thanks for your support and the link to the interesting bladeforum.

Ken, I am sorry if it looks overly complicated, but "a perfect formulation of a problem is already half its solution". Please be so kind and try to digest the annoying physical terminology. May be also my wording makes it difficult, sorry for that. 

Jan

[Ken S]

Jan,

I enjoy your posts! You would be a good professor guiding your students. You are quite correct in saying that we need accurate vocabulary. I will spend some quiet time this weekend digesting your ideas.

BESS shares the same difficulty our jig designs have. We need the mathematical logic and precision beyond the everyday use requirements to keep things "within tolerance". We also need the product, be it a jig or BESS to be simple enough for those less trained in mathematics to comprehend.Dutchman's grinding angles booklet comes to mind. I think Ton (Dutchman) did a fine job and produced a very useful work. It is the foundation stone of my kenjig projects, and, in my opinion, has much more untapped value. It did require some concentrated thought and effort for me to be able to use it. I think my mental effort was well repaid. I tried to made Ton's ideas "stone simple" with my wooden jigs. The simple jig can easily be made in a home shop in just a few minutes with scrap lumber and no math beyond basic measuring. Sadly, Ton's fine work seems beyond the interest of most of the forum. Math can be intimidating for those of us who work in jobs which are less math centered.
,
Like the kenjig, the edge testers and testing using BESS standards are straightforward and easily mastered. The basis is well developed math and logic. The presentation is "pro publica". We need both.

Do not worry about being critical of me. I know your intentions are only good and I grow from being challenged to do better.

Keep up the good work!

Ken

[Jan]

Ken, thanks for your feedback. I certainly am professionally deformed after lecturing for a couple of years.

I have never wanted to be critical of you, my intention was to encourage you to an effort necessary to adopt the accurate vocabulary for the BESS approach description. You have a potential for it and it will be well repaid. Mike B. has written to me "... now though, there has been a push made from several different areas of industry to express the BESS in more specific and generally accepted engineering terms."

Jan

[Ken S]

Jan,

I have always interpreted your comments as encouragement rather than criticism. As one of our members says, "One man sharpens another".

Ken

[Jan]

Touché, Ken! 

Jan

[Ken S]

 

[Ken S]

I have reread Jan's reply number thirty. I am usually up by four am. This is my quiet study time of the day.

Jan, you are correct in differentiating force by unit area. What comes to mind for me are chisels. Given the same driving force, a quarter inch (6 mm) wide chisel will penetrate wood deeper than a two inch (50mm) width chisel. I often grind wide chisels with a slightly more acute bevel angle. The force of the mallet is distributed over a wider area.

With a knife edge using a BESS tester, the only part of the edge involved is the portion of the edge which contacts the test media. In chisel terms, this would be like using a wide chisel to chamfer an edge, where only a fraction of the edge makes contact with the wood.

What would impact the BESS reading more directly would be the bevel angle of the edge. The very acute bevel angle of a paring chisel or knife would give a lower reading than the more obtuse angle of a meat cleaver or mortise chisel. A skilled sharpener should be aware of this.

In my case, the primary purpose of using BESS measurements is to determine how sharp an edge is compared to when the knife was new, or to measure the effect of sharpening, honing and polishing procedures on the sharpness of the edge before and after. This can measure steps along the way as well as in entirety. We must factor in the intended use for the tool. Our most useful comparison for the edge of a meat cleaver is how sharp the sharpened edge is compared to how it was after use in the kitchen. We should not be ignorant of how this reading compares with a paring or fillet knife, however, we should realize that this is like comparing apples with oranges.

As a telephone repairman, customers would often tell me there was a short on the line.  "A short on the line" was their catchall term for trouble. Given my training, for me a short was low electrical resistance between the two conductors of the pair of wires which composed their line. This was different than a cross, which was low resistance between conductors of different pairs; a ground fault, which was low resistance between one or both conductors and the earth; or an open circuit where one or both conductors had high resistance (often a complete break).

The customer did not really need to know the difference. (Ideally he would know.) As a troubleshooter, I did need to know.

I look at BESS readings the same way I see other measurements. My scoop of coffee in my Melitta filter earlier this morning was not terribly precise. When I developed photographic film, I measured the water and chemicals in grams and milliliters. I needed to be more precise. In my opinion, one of the benefits of BESS is being able to work quickly and to be more precise when desired. Jeff Farris made a good comparison between the Tormek leather honing wheel and using different grits of very fine waterstones, the Tormek leather honing wheel gives ninety percent of the benefit in twenty percent of the time. Jeff's point is well made, even if the percentages are not precise.

I can make BESS readings of an edge with a relatively inexpensive test set up in a very time efficient manner. I can share them and have them understood and repeated. I can use more exacting individual measurements or use a quicker "go-no go" method where if the test media is not cut with a certain gram weight, the edge is no go.

We do need precise terminology. Thanks, Jan, for reminding us.

Ken

[Jan]

Congratulations Ken, you have famously retold the BESS approach. 

You are correct, the driving force per unit area (pressure) is the most important factor by cutting, because this describes the concentration of the applied force. If this concentration (pressure) is high enough, than the edge breaks the bonds in the material and cuts through it. 

Mike B. wrote me, that BESSU is able to express the physical dimensions of the "standard" cutting edge of a razor blade in terms apex width and radius in nanometers.

Jan