Thinness of the edge apex

[admin]

Maintenance post. Please ignore.

[KnifeGrinders]

To what Mike has said above, I want to add that selecting a DE razor as a reference point for the start of the BESS scale was very clever from every point of view - practical, empirical and theoretical.
So clever that bears the impress of genius.
The more scientific data we get around it, SEM, wavelengths, etc, and the more of a collective brain accumulates on this forum that reflects upon it, the more obvious it becomes.

On the other hand, selecting the DE razor blank for the other end of the BESS scale is of course just a practical convenience of handling the same blade.
If they happened to be half that thick, the BESS scale could as well end at 1000.
The BESS scale upper end should change with time, getting tied to some better empirical and theoretical reference point, and since I strongly believe that Mike's BESS scale will outlive us all, the present 2000 BESS end of scale will become no more than of a historical value.

[Jan]

The DE razor blade standard reminded me the history of meter, the base unit of length in the SI.

• Originally meter was defined as 1/10 000 000 of the distance from the North Pole to the equator.
  
• Since 1899 meter was defined as the length of a bar made of special alloy of platinum and iridium at the temperature of melting ice.
  
• Since 1960 meter was defined as a certain number of wavelengths of krypton lamp (0.64 μm, red-orange colour).
  
• Current definition adopted in 1983 uses the speed of light in vacuum.
  

Jan
 
P.S.: National Prototype Meter Bar No. 27, made in 1889 by the International Bureau of Weights and Measures and given to the United States, which served as the standard for defining all units of length in the US from 1893 to 1960. (Source Wikipedia)
   

[KnifeGrinders]

That's a fascinating analogy, Jan!

DE safety razors were first picked by BESS as a standard for a minimal measurable unit because they are the sharpest edge reproducibly manufactured and commonly known.

Following SEM studies, came realization that it is also next to the limit practically achieved of a steel blade with the finest honing, at or under 0.1 micron.

Thanks to Jan, we now also see it as an edge past the limit discernible by a human eye in the visible light of the shortest wavelength.

Nowadays for us it is not just 50 gram-force, but also 0.1 micron edge apex in the order of extreme ultraviolet wavelength.
With all the enriched meaning, it has shaped into a BESS unit that is more than just a number of grams necessary to sever a test media.

An edge score on the BESS scale tells us not only of gram-force, but also of the edge width and something else, and therefore shouldn't it be more appropriate to name the score BESS Unit rather than grams or g-f?
50 BESS or 300 BESS etc, as we already do in Australia.

[EOU]

We think you're right KnifeGrinders. Defining the lower end of the BESS was a breeze. We'll all call BS! when someone reports a BESS score of zero. BESS scores that lie toward the upper end of the scale seem to have importance only with some of our industrial customers. We have industrial customers who sharpen to 600 and replace or resharpen at 900. 

Things do change though and Jan's post is an excellent example. By the way, there was a book that floated around the office here written about a French scientist who was first tasked with defining the length of a meter. As Jan said, first he had to determine how far it was from the pole to the equator. No small task when lacking a tape measure of that length. The English were determined to define  measurement based on some common object, a human body part or the height of a horse. Europeans, especially the French, wanted to base measurements on the physical universe. I have to admit, the French got it right but, nonetheless, we all, here at EOU, have to mentally convert everything presented to us in metric to standard before  we can grasp it. 

The French got one more thing right; the steering wheels of their cars are all on the correct side of the vehicle. Of course, no offense intended to those who have not yet seen the error of their ways.  It would be a simple thing to correct; move the headlights to the rear and the taillights to the front. Then turn all the road signs 180 degrees. Voila! You'd now be driving on the correct (right) side of the road! 

[Jan]

An edge score on the BESS scale tells us not only of gram-force, but also of the edge width, and therefore shouldn't it be more appropriate to name the score BESS Unit rather than grams or g-f?
50 BESS or 300 BESS etc, as we already do in Australia.

The reason why I have recommended to use the gram-force (gf) unit for BESS measurements is the fact, that physical quantities should be expressed as the combination of magnitude (number) and unit.

The standard unit of force in SI system of units is Newton (N), but for BESS purposes it is more convenient to use gram-force (gf) which is a gravitational unit of force. One gram-force is equal to the force exerted by one gram of mass in a standard gravitational field.

In the BESS concept the force necessary to reach the critical contact stress to cut the test medium is a measure of edge sharpness. Under some assumptions this force can be converted to the edge apex width.

For low BESS readings the relationship to edge apex width is linear but for readings near the top end of the BESS scale the relationship is different.

Jan

[KnifeGrinders]

Then shouldn't the dull end be cut off at where it is not linear any more?
1000 BESS or 1 micron edge is a good candidate.

[Jan]

Yes, for the lower part of the BESS scale it would be possible.

Jan

[EOU]

This is a good conversation and we hope not to mess it up. We do have information at hand though that might be considered useful.

So first, a little history on how we express BESS measurements. First, we had a goal; to developed a sharpness scale that was useful and easily understood by everyone, scientist or layman. We also wanted it to be relatable and that's where DE razor blades entered the picture. In the USA, the term "pressure" is readily substituted for the more appropriate term "force".  We are told to apply pressure to open wounds, not force. Any American homechef, in complaining about his/her dull knives, would describe the excessive pressure he/she had to apply in order to sever that evening's  pork loin into chops. When we first introduced the KN100 we spoke in terms of how many grams of pressure were required to sever a test media. Jan was the first to raise this question with us and it became obvious to us that we needed to take a step toward the scientific so that not only Americans felt comfortable with our terminology and descriptions, but everyone else as well. We then adopted Jan's suggestion in our literature. Now, there seems to be  interest in further dissecting this description.

For us this is simply a matter of convention. We calculate in feet and inches around here. Some would say that this is the English method of measurement, others would say it is Standard and yet others might say it is the Imperial system. There are arguments for which is the most correct but we all understand what the other means, feet and inches. At EOU, we speak of "BESS Scores", but typically we just say or write 150, or 234. If pressured to explain further we would simply say "It required 234 grams of force to sever the test media." If someone feels that it is better described as "gu" or "gf" that's fine with us because we understand your meaning. If different conventions arise in different parts of the world, that's just fine with us as long as we continue to understand one another. 

Abbreviating the BESS at 1000? Here's the issue; If you manufacture common axes and hatchets 1000 may not be dull, it might be just right.  If you are trimming composite plastics with circular blades 1000 might be too sharp. Our concern is that we might find that the published  scale doesn't go high enough (although, in a practical sense, that is an instrumentation issue as opposed to a real scale problem). If someone wants to think in terms of the scale ending at 1000, that's fine. I can promise you that many knife sharpeners would be fine with a BESS that ended at 500. 

Just one more item and this is simply a matter of how one sees the world. BESS certified instrumentation and test media, via a process of interpolation and derivation, posits on the  thickness or thinness of an edge. This posited conclusion is then displayed to the user as a BESS Score. It is not displayed as an actual, physical measurement of the edge apex, but rather, a score. Can the two, BESS Score and apex width, be linked? Of course, they have to be linked or the system wouldn't be of value. The value of this linkage is where the question lies and we refer back to our opening comments. If we tell you, or anyone, that an edge is, in fact, as sharp as a razor blade, then that has meaning because they can relate to it. If we tell someone that the edge has a radius of 50nm then what does that mean to the average Jack or Jill?

It's like this though, scientists argued for decades over whether 0C or 32F (can't remember which) should represent the freezing point of water or the melting point of ice. We can't remember who the winners were either but a little good debate on the finer points of the BESS will never hurt anyone and is likely to help.

[grepper]

An interesting factoid is that the original Celsius scale was reversed, “In 1742, Swedish astronomer Anders Celsius (1701–1744) created a temperature scale which was the reverse of the scale now known by the name "Celsius": 0 represented the boiling point of water, while 100 represented the freezing point of water.”
 
“The Celsius scale was based on 0 °C for the freezing point of water and 100 °C for the boiling point of water at 1 atm pressure following a change introduced in 1743 by Jean-Pierre Christin to reverse the Celsius thermometer scale (from water boiling at 0 degrees and ice melting at 100 degrees).”
 
https://en.wikipedia.org/wiki/Celsius
 
I’m glad EOU did not make the BESS scale reversed.  Considering how sharp folks are getting their blades these days we’d have to be talking BESS numbers like 5,000!