Question of where the EOU edge sharpness testers can be used and where not, has popped up too often through the last weeks for me not to bring it up here.
People seem to confuse edge sharpness and cutting performance testing.
Though there are other makes, a classic cutting performance evaluation tester is the CATRA Tester .

Here's how I see the difference in areas of use between the edge sharpness and cutting performance testers - and will appreciate your input.

Edge sharpness testers use a thin line test media, and the testing action is a point cut.
Cutting performance evaluation testers use a thick sheet test media with a wearing effect on the edge, and the testing action is a depth cut.

An edge sharpness tester tells you how sharp the edge is, which reflects only the 1st phase of cutting - penetration.
Edge sharpness tester scores have no bearing on the blade angle and profile because of that.
A cutting performance tester also tells you how effective the edge angle and blade profile is.

Edge sharpness testers have two primary purposes:
- monitor edge durability of the same blade over time;
- improve and streamline sharpening protocols.

Edge sharpness testers cannot be used to compare cutting performance of blades of varying geometry, and determine which one is superior to another.
Edge sharpness testers can be used to compare performance of blades of similar geometry but made of different steel.

I can put the same sharp hair-splitting edge on blades from 12 to 50 included angle, but they won't cut the same, and an edge sharpness tester can't tell me which will cut better.
Or can?

Picture: PAUL HOGAN "CROCODILE DUNDEE"

Hello everyone. We just received information from our master distributor in Australia/New Zealand (KnifeGrinders) that the Adelaide Knife Show will be convening soon. If you're interested in seeing a preview of some of the beautiful work that will be seen at the Adelaide show,  please follow this link; https://www.facebook.com/theadelaideknifeshow/  There are some very talented people down in that corner of our world. 

How about we all pitch in for gas money so that  our own Mark Reich with Reich Precision can travel to the show as our BESS Exchange representative?  Does anyone know how long it takes to drive from the Black Hills to Australia? We might have to come up with lunch money as well. Anyway, Mark would certainly give them all a run for their money with his beautiful knife creations.

One of our PT50As will, once again, be serving as judge for the sharpest knife competition at an international show. A big THANK YOU to KnifeGrinders and Australian Knife Magazine for organizing and sponsoring the competition.

For the BESS community it is important to understand the relationship between edge sharpness, BESS readings and thinness of the edge apex. Because the edge width of a DE razor blade is only 1/10 th of one micron we have no direct personal experience with such a very thin piece of metal.

On the other hand from personal experience we know that the sun light may be separated by prism into spectral colours. Each spectral colour can be associated with some wavelength of light. The wavelength of violet colour is approximately equal to the edge width of a sharp knife.
   

The visible spectrum goes from violet colour which has a wavelength of some 0.4 micron to red colours with some 0.7 micron.
   

When we measure BESS 200 gf on a sharp knife, we know that the edge width should be some 0.4 micron*. This edge width is equal to the wavelength of a violet colour!

Similarly, when we measure BESS 300 gf on a knife we know that the edge width should be some 0.5 micron, which is equal to the wavelength of a blue colour.

Jan

*P.S.: I.e. 4 times more than DE razor blade which has 0.1 micron edge width and 50 gf BESS.

Gees. I feel kinda silly for not thinking of this sooner. By far, the most common single bevel edges are... Scissors! Everyone has lots of single bevels right under their noses!

For the stickler, I use the words "scissors" and "shears" interchangeably simply because almost everyone does. Hair cutting scissors are most often erroneously called "hair shears", so that alone totally skews the field. At any rate, I don't mean to make any distinction. I guess "shear" is easier to spell than "scissor", and most people probably think "shear" sounds more professional than "scissor".   

Hair scissors can be very expensive, and sharpeners usually get $20-$30 per scissor, which makes them one of the most lucrative items to sharpen. Hair cutters know absolutely nothing about sharpening, but they sure can tell if their scissors are less than perfectly sharp within about two snips.

Once upon a time, I wanted to be a professional sharpener. Miraculously, I ran into Mr Rupert, the man who would prove to have the greatest influence on all of my sharpening related items of interest. With a lot of Mr Rupert's help and guidance, I traveled thousands of miles to learn to sharpen hair scissors from the likes of Bob Crilly, and learn firsthand from several more successful, dedicated sharpeners. 

It's almost a secret that professional scissor sharpeners never touch the flat side of the scissor. They know how important it is to keep the flat side "factory flat" for the life of the tool. They "deburr" (I would say "distress") on a popsicle stick or whatever. 

Now, case in point. A Master Gardener friend brought her manual hedge trimming shear in for a sharpening yesterday. It was a well used tool, but it had been pretty carefully maintained with a file. It wouldn't cut anything Cleanly though, because the flat was not flat all the way to the edge. 

I made a single, slow pass with a used 60 grit belt to reprofile the bevels. I needed to remove enough of the edge to get rid of the "unflat", which means I needed to grind the bevel back a full 1/16". I ground the bevel edge leading on the vertical platen, with the flat facing me, so I could see when the edge was ground back to the flat plane.

This produced a pretty big burr on the flat side of the blades. If one is very careful about placing the flat on a flat stone, it is possible to remove the burr while maintaining the flat. I used an Atoma 400, so it took less than 10 seconds to deburr both blades. I pronounced them "sharp", stepped out onto the lawn, and tried them on grass. Wow! They cut beautifully, especially for a 90 second sharpening job. I thought I better make the most of it.

Just for fun, I told the Master Gardener that only a master sharpener could make hedge trimmers sharp enough for a haircut, to which she heartily agreed. I got my hank of human hair, and made several snips along the whole length of the blades. I might as well have had a $1000 pair of Japanese hair shears. Honestly. 

I have to admit this was a good showing of a fresh edge, but pretty typical for any single bevel. With decent carbon steel and good stones or plates of medium grit, there is no deburring. That's my definition of efficient. 

Many Japanese blades take it a step further by hollow grinding whenever they can, so keeping a flat side flat is easier.

I start with the conclusion, and then list arguments; you can do your own analysis of the sources I give, or just take my word for it:

50 BESS approximates to 0.1 micron in the razor range of the BESS scale (10-100).

Sources

Chase Anderson's raw data of DE razors sharpness by PT50A, including that of Feather, Gillette, Wilkinson, Kai, and Derby brands.
https://www.refinedshave.com/razor-blade...s-testing/
Thoroughness of his measurements is worthy of respect.

Todd of the scienceofsharp.wordpress.com also known as ToddS on bladeforums.com and fuzzychops on straightrazorplace.com
Todd, a professional with access to SEM microscope, gave edge apex width for Feather, Gillette, Wilkinson, Kai, and Derby DE razors.
http://straightrazorplace.com/honing/968...rop-5.html
https://bladeforums.com/threads/how-low-...402/page-2
https://scienceofsharp.wordpress.com/

Correlation

avg. 32 BESS, Feather (variation 30%) - 0.05 micron 
avg. 46 BESS, Gillette & Wilkinson Sword (variation 15%-47%) - 0.075 micron (I took an average of the 0.05-0.1 given by Todd)
avg. 53 BESS, Kai & Derby (variation 16-33%) - 0.1 micron 

Approximations

As seen from the raw data at http://www.refinedshave.com, where BESS measurements are taken at 4 points along each razor edge, variation in BESS scores is huge, up to as much as 47%.
This is because the razor edge itself is far not that even in width as one would expect a priori.
Test clips used in that measurements vs BESS-certified media have difference in readings less than the dispersion on razor edges, and can therefore be neglected.

SEM measurements depend on the person expertise and subjective judgement.
Even with fully trusted SEM numbers, we know they were not taken on the same razors that were BESS-tested, let alone not on precisely the same points of their edges - we therefore can expect at least the same variation in results as we see in BESS scores along the edge.

CONCLUSION
I know it is oversimplified, yet to a first approximation it can be taken that with the step of 25 BESS, this correlation might be linear.

25 BESS = 0.05 micron edge apex width
50 BESS = 0.1 micron edge apex width
75 BESS = 0.15 micron edge apex width
100 BESS = 0.2 micron edge apex width

This is in line with Mike Brubacher's findings, summarized in the "The Science Behind Edge On Up Instrumentation and BESS Test Media" section of the "Support Document for All Edge Tester Models" available in the EdgeOnUp library.

This is an excerpt from my article in the Australian Knife Magazine.
Australian Knife Magazine is a printed magazine, and I seriously doubt anyone in the US will ever have a copy unless I send them, but I won't.
I therefore thought making this data available to the BESS forumers. 

Knife community uses a set of fanciful terms to describe sharpness.
These terms, although not academically endorsed, are full of meaning as they come from real life, flesh and blood cut off our fingers.
They may sound vague and not clearly defined, but are discriminating enough for us. We readily distinguish a work sharp edge from shaving sharp, and will never confuse a scary sharp knife with crazy sharp.

Sharpness reflects the very edge itself, not overall performance of a knife, which is subject to cutting tests and not discussed here.

On the one hand, we have our informal classification of sharpness, like working edge - sharp edge - fine edge etc (I am listing the full terminology in a paragraph);
on the other hand, we have a set of tests telling us how sharp the knife is, like thumb pad test - fingernail test - shaving test etc, and again I will give a complete list of these tests further on as they are so inventive that can capture imagination.

Armed with a BESS PT50 edge sharpness tester and a few hundred knives from our rental pool and my collection, started I my study, full of curiosity and apprehension.

DEGREE OF SHARPNESS
Dull - an edge over 500 BESS.

Butter knife is a classic example of ultimate dullness.
Plastic knife from the last Sydney Knife Show cafe scored 1750 BESS;
Plastic knives they give us at airlines are 2000+ BESS.
An edge over 500 on BESS scale requires sharpening.

Sharpness in the range of 200-400 BESS.
Working edge, real world sharp is within 300-450 BESS.
Sharp we call an edge at 250-300 BESS. Quality cutlery out of the box comes that sharp.
Very sharp - most people consider it an edge between 130-200 BESS.

Fine knife edge takes us to the quarter of a micron level, 100-150 on BESS scale.
Shaving sharp - edge starts scraping shaving at 160 BESS - and we will discuss all the gradations in the Sharpness Tests section later.
Nuts sharp referred by knife lovers is an edge at 0.2-0.3 micron, 100-150 BESS.
Scary sharp edge is at 0.2 micron or scores 100 BESS.

Further to the submicron level, under 100 BESS, we start talking of keenness rather than sharpness. 
Not many people have the skill, knowledge, or equipment to reproduce this edge.
Crazy sharp starts just under 0.2 micron, from around 90 BESS.
Razor sharp – for example, a double-edge Schick razor from Woolworths is 30 BESS.
Knife edges in this range have insane-this-should-be-illegal levels of sharp.
Wickedly sharp is a term reserved for edges under 0.3 micron, which is less than thickness of a human hair cuticle.

And finally, esoteric sharpness.
A silk scarf dropped on the edge cuts in half by itself.
Sharp enough to shave a gnat’s ballbag.

SHARPNESS TESTS or HOW TO KNOW HOW SHARP IS YOUR KNIFE

Now that we have the edge sharpness tester from Mike, these tests are no more than historical for me, but I will always be feeling sentimental about them as they've been the only means guiding my sharpening for decades.
Values I give further is the earliest attained sharpness (from the dullness end of the range) when the test can be performed cleanly.

Thumb Pad Test - feeling the edge crosswise with the ball of your moistened thumb. Draw your thumb across, not along, the edge to feel how it grips into your thumb print. If the edge tickles your thumb the knife is not dead dull. This is a widespread belief; our tests, however, show it is false.
Just today an electrician brought me his knife to sharpen, which scored 795 BESS, yet it still tickled my thumb.
Too subjective to be a useful test.

Fingernail Test - resting the edge with its own weight on your nail check if it catches. When it sticks, it is sharp. If the edge glides over your nail, it is dull.
I’ve tested a dozen of knives from 800 BESS edge down to 200 with a 50 BESS step to determine the catching point, and the fingernail test becomes positive at 350 BESS.
This one is a truly useful test as it tells you have a working edge.


Whittles soft wood (e.g. pine) – becomes positive at 150 BESS.
This is shaving range, which has a number of well-defined gradations that we will discuss at great length after the paper tests.

Paper Tests

Roughens & tears paper – a knife starts tearing paper at 600 BESS, not duller.
Obviously, such a knife requires sharpening.

Slices 80gsm printer paper – a knife can do it at 450 BESS, which is the upper limit of the working edge.
Not a very clean cut initially, but already effortless; the sharper the edge the cleaner the cut.

Slices newsprint – this is somewhat more demanding, and indicates an edge within a good working range, at minimum 400 BESS.

Slices a sales docket/receipt – as these dockets are very thin, the test is even more demanding for sharpness, and becomes positive at 300 BESS.
When positive, this test takes the edge from just working to sharp.

Filleting printer paper, i.e. shaving off layers of 80gsm paper not cutting through, first demonstrated by Sal Glesser in his Spyderco Sharpmaker video.
I’ve tested a good dozen of knives slightly differing in sharpness to precisely determine how sharp must be an edge to be able to shave paper – at 130 BESS or a quarter of a micron.
Pretty sensitive and precise test, indicating a very sharp fine edge.
Only knife that sharp will cut a circle in light printer paper.


Toilet paper test - push through then slice down a single ply toilet paper. Possible at 50 BESS.
The main challenge of this test I found was to harvest that single ply. Unfortunately, nowadays this test is losing its standardization power since the test media is losing the line of distinction with the facial tissue.

Shaving Tests

Scraping shaving – a toothy edge is capable of catching hairs on the skin, but instead of cutting them it “rips” them out of your skin: 160 BESS or about 0.3 micron.

Shave against the skin - won't shave arm hair above skin, but shaves touching the skin without trouble.
This test has two gradations:
- with the grain of hair – 140 BESS; and
- against the grain, which requires way better sharpness in the vicinity of 0.2 micron, 95-100 BESS.

This is the level of sharpness the knife community refer to as “nuts” and “scary sharp”. You can recognize an owner of that sharp knife by "the bald patch of glory" on his forearm.

Shave without touching the skin, cutting hair at the base of the strand. Becomes possible at 40-50 BESS or about 0.1 micron edge.
Such a knife is not just shaving sharp, it is razor sharp.

Tree topping – where you can run the edge down above the skin and cut free standing hairs in the middle.
I spent an hour maybe to precisely determine the edge width capable of top trimming. After I ran out of forearm hair, I turned to my thighs, and funnily enough discovered two gradations:
- tree-topping on the leg is achieved easier, at 35-40 BESS;
- tree-topping on the forearm requires sharpness under 0.1 micron, 25-30 BESS.
With a knife that sharp you can smooth shave your face without pulling on the whiskers.

Hanging Hair Tests

Human hair cuticles average 0.3-0.5 micron in thickness layered like roof shingles. Cutting edge must be within this range of thickness to penetrate between them.
Due to the fact that there are up to 10 layers of cuticles, it is possible not only to split the hair lengthwise, but also whittle curls off a hair.
The test is performed with the edge angled to the root side of a hair for the edge to catch between the cuticles, at about 2cm out from where your fingers grip the hair.

Violin sign - the hair doesn't cut, but it "plays violin" with the edge.
This is due to the hair cuticles catching the edge, which is not sharp enough to penetrate. You can sense the violin-like vibrations, and with certain blades even can hear a faint ringing sound.
I’ve been testing edges over and over again at 10 BESS steps until firmly determined that your knife starts playing violin at 115 BESS or 0.2 micron.
This one is a highly precise test.
From this point you are ready to delve into the true razor-sharp level, not just shaving-sharp.

Cut a free hanging hair - becomes possible at 70 BESS or 0.15 micron.
You cannot split the hair yet, but already can slice it. Note that at this stage it is not a popping cut, you have to slice the hair.

Split hair - the edge catches the hair between cuticles and splits it lengthwise.
60 on BESS scale is where the edge starts splitting a hair.


Hair popping - the severed hair part will jump away as soon as it touches the edge.
Requires at least 30 BESS or under 0.1 micron edge. I couldn’t make hair pop with 35 and 40 BESS edge.

Whittle hair (cut curls off a hair) – becomes possible at 25-30 BESS.


Silent slicer - at 20 BESS or under the hair falls effortlessly as soon as it touches the edge; not jumping away like with popping, just silently falls.

And finally, Tongue test – a sharp knife tastes like metal, and really sharp like blood.

Thanks to Mr Grepper's amazing narrative, I don't think there are many details left unturned about the M3, so I'd just like to pass along my general impressions.

As a stand alone product, I like the quality of the diamond and ceramic rods. The angle guides on the handle are a great idea for a diamond or ceramic rod sharpener, but they were cumbersome until I started turning the handle from side to side.  

I was most impressed with the edges from the diamond rod. They would normally measure about 250gf, but they cut rope like crazy compared to edges finished on the ceramic. 

Going strictly by the directions, I found no redeeming value to micro-forging. I read about the testing at Benchmade's facility, and I found that to be pretty accurate. When they were testing, micro forging dulled the blade, but after what sounded like quite a bit of use, the micro-forged edge caught up.

The "catching up point" didn't materialize for me. It was too far beyond "dull".

The whole idea of sharpening a blade just so you can destroy the edge and almost get it sharp again is beyond me, but IMHO this must be geared toward light home kitchen use on soft steel.

If any type of gadget helps the average person think about sharpening their knives, that's a good thing.

I had the pleasure of a long telephone conversation with Rupert recently. Rupert has long experience converting belt grinders. He is also very generous in spirit, and wants to share the benefits of his experience with other sharpeners. We talked about making the benefits of the "Generation III" Viel belt grinder available to bessex exchange members at a reasonable price. None of us are in this venture to make money. Here are two options:

Either option requires purchasing a basic Viel belt grinder (without a motor) and a variable speed motor kit (from Penn State Industries).

The first option would be suitable for a "home workshop" person. I would have opted for this if it had been available when I started. The kit includes an already drilled aluminum bracket, a smaller Viel pulley already bored to fit the PSI motor, the misc. hardware needed, a paper template, and instructions. Two hours of shop time should see the project completed or well along. The price of this has yet to be determined and will depend on material costs and the number ordered. More orders lowers the cost per unit.

The second option can also be completed in a more complete home workshop. I did mine with a battery drill and a bandsaw. A drill press would be useful, but not mandatory for this option. This option consists of a downloadable paper drilling template and instructions. This would be downloadable from the bess exchange at no cost. The user would need to purchase a smaller Viel pulley bored or needing to be bored, and an aluminum bracket plus the misc. hardware locally.

More information will be posted on this bess exchange later. Those who are interested in either option should post their (non binding) interest on this topic. Questions are welcome.

The modified Viel is a very useful, versatile tool. We really like it!

Ken (for Rupert and Henry)

I recently rebuilt my Viel grinder with a smaller (3 1/2” instead of 6”pulley). The driven, top pulley is the original 3 1/2”.

Many years ago I purchased a right angle adaptor for my electric drill. The adaptor could be installed two different ways: one gave higher speed and lower torque; the other gave lower speed and higher torque.

For ease of calculation, let's round the pulley diameters to three and six inch diameters and use 1000RPM. My gut feeling is that the smaller pulley, with lower surface feet per minute will produce more torque, however, my gut feelings are not always very scientific. Once again, my high school math background from fifty yeats ago is not up to the task. 

Help will be most appreviated. What is the effect on torque from using the smaller pulley?

Thanks,

Ken

What is the "P" grit rating for the diamond sharpening wheel?

What is the "P" grit rating for the pre loaded honing wheel?

Tormek validates? that two grits will get kitchen knives sharp.

The T-2 knife guide/jig may be adaptable to the Viel and or Kalamazoo SM 1?

Rupert