For many years I have had a hobby interest in the history of machine tool technology and measurement. We owe much of our present standard of living and computer age to the nineteenth century pioneers who gave us accurate and repeatable measurement standards.
While mathematician Pierre Vernier lived during the time of the Mayflower pilgrims, the Vernier caliper was not invented until the mid nineteenth century. This, and the micrometer, which was invented around the same time, gave machinists the ability to measure within .001". By the 1890s, with the invention of Johannson measuring blocks in Sweden, we could measure in millionths of an inch.
Today, an engineer can email drawings of parts to machinists throughout the world and expect the parts to fit. The drawings include the acceptable tolerances of size and degree of finish. We have standards for different fits: sliding fits, friction fits; fits for threads, including different fits for the precision or lack of precision of the thread application.
These tolerances can be measured with very sophisticated lab equipment or with tools generally available on the shop floor. Naturally, the shop floor equipment will not have the precision of the lab, but it is usually sufficiently accurate.
Surface roughness can be gaged with sophisticated digital readout equipment with probes. Or, it can be measured on the shop floor by using samples of accurately finished small pieces of metal of known finish roughness.
Do we as knife sharpeners have something which will be more accurate than our fingernails or slicing pieces of paper? How would we communicate to other members of the forum or other sharpeners around the globe how sharp an edge actually is? We do not need several thousand dollars of digital lab equipment. Is there a simple piece of equipment which can produce accurate and repeatable sharpness measurement?
Yes, fortunately, we now have the Brubacher Edge Sharpness Scale (abbreviated BESS). This is an accurate simple standard which measures how much weight is necessary to cut through a polymer thread of known strength with a knife or straight razor edge. This feels very natural to me.
As a telephone installer and repair technician, I routinely measured circuit noise. Listening for noise with only an ear is very primitive. By using test lines and measuring in decibels, I was able to precisely measure and verify if the circuit was within guidelines or needed to be repaired. I was able to do this with a small meter I carried on my shoulder. The BESS system allows knife sharpeners the same precision and repeatability.
I have recently begun working with a BESS machine. I will post my results when I have more experience with it. I believe this advance has much to offer knife sharpeners who work in a home shop instead of a company lab. Stay tuned.
Ken
This spring I tool part in a knife sharpening competition. We had use of two commercial testers plus the subjective opinion of a local chef. The results - 3 tests times 3 knives per sharpener - were overwhelming. I quite agree a simple test method is desirable.
I was the contact person for the CATRA tester from the UK and had two weeks use of a CATRA tester. The CATRA uses a slow motor drive to press the knife into an 8mm rubber rod, which is curved so it parts after cutting to prevent side friction. WAY too complicated.
The KN-100 sharpness tester is a model of simplicity, using gravity to power the cut, simple test media, and a single number (weight) as the test result.
I saved 10 test samples from the CATRA and I was impressed that they showed excellent correlation between the $160 KN-100 and the $12,000 CATRA.
The knife edge sharpness tester I have been using is the model KN100 by Edge on Up. This cleverly designed machine tests the sharpness of an edge by determining how much weight is required for the edge to cut through a polymer thread of known strength.
In many ways, this edge tester reminds me of the Tormek. The Tormek can be used to quickly replicate an existing edge to full sharpness. With a skilled operator, the Tormek can also be utilized to modify edges for individual applications. The versatility of the gouge and drill bit sharpening jigs are examples of this flexibility.
With the KN100 edge tester, it can be set up to quickly decide "pass-fail" for an edge or to acurately determine just how keen or dull the edge is. The testing can easily be repeated and noted using different sharpening methods; during different stages in sharpening; or measuring edge degradation after varying periods of use. As with the Tormek, the limitations are mainly determined by the limitations of the user's skill and imagination.
The unit is very well conceived, designed and machined.The minor amount of assembly is easily finished in a minute or two. Included with "set up" is gathering some components. A digital postal scale is most useful. There are a variety of these available in the $15 to $40 price range. I purchased an American Weigh Scales model PS-25. It was just under $20 on Amazon. It has four modes, Kg and grams; grams; pounds and ounces; and ounces. It works with either two AA batteries or the included AC adaptor. An important feature to be aware of is the size of the weighing table. The PS-25 has a weighing table of 5 ½" x 7" (140mm x 180mm). The smaller dimension is critical as it allows the KN100 to set on the scale.
Another consideration in choosing a scale in the maximum weight. The PS-25 can weigh up to 25 Kilograms or 55 pounds. This is certainly usable, but it far exceeds the amount needed. Ten pounds is more than enough. The constraint with larger weights is the weight of the calibration weight. The weight used to recalibrate the PS-25 scale is 10 Kilos, or 22 pounds. I made up a satisfactory test weight by combining the milling table from my drill press with a peanut jar partially filled with misc. hardware. It is accurate, but clumsy.
In my opinion, this is the easiest, most efficient way to use the KN100. Just set the KN100 with the knife in place on the weighing table. Push the "tare" button on the scale. The scale subtracts the weight of the KN100 and knife from the measurement. Therefore, the readout is just the measure of the added weight used to cut the polymer thread. No math is needed. The readout is the final measurement.
Small lead shot is the manufacturer's preferred weighing media. BBs, sand or water can also be used. Lead shot or BBs must be used carefully to avoid scattering them. One useful formula is that one liter of water equals one kilogram of weight. I have thought of using water, as I happen to have a collection of graduates left over from my photographic darkroom.
I followed the manual's recommendation of purchasing a pack of 2000 BBs from Walmart. The cost was around ten dollars US. I have numerous empty peanut butter type jars and 35mm film cans. The smallest plastic peanut butter jar will easily hold all the measuring weight one could use with the KN100 (2000 grams). I made up and labelled a jar with 375 grams. 375 to 475 grams is the listed weight in the manual for "High End Cutlery (factory edge)". I made up a film can with 100 grams.
I tested my two paring knives. The second knife tested, the knife I rarely use, curt through the polymer test thread with the 375 gram jar. (I placed the jar upside down on the flat lid to mate well with the KN100 surface.) With this test, I knew that the edge, at least the area of the edge I tested, was at least at the top sharpness of factory edges for high end cutlery. Using my "pass-fail" mode, this knife was definitely a pass.
If the 375 gram jar would not cut the polymer, I would have added the 100 gram film can. If these together cut the polymer, I would be within within the range of "factory edge".
My other paring knife, the one I use a lot, required approximately 625 grams to cut the polymer. According to the chart, 650 – 700 grams is "Typical Knife Edge in Need of Sharpening". I agree. My other paring knife stuck to my thumb nail; this one did not.
1200 – 1400 grams is listed as "This Knife Edge Found in Many Kitchens". 2000 grams is the inner flat edge of a double edge razor or a butter knife.
When I attended elementary school in the 1950s, the grading system was Excellent, Good, Satisfactory, and Unsatisfactory. I would grade edges which can cut the polymer with less than 375 grams as Excellent. An edge needing 375 to 475 grams woul be Good or Satisfactory. Any edge needing 650 grams or more would be unsatisfactory. For edges duller than 650 grams, we might switch to the ABCDF grading system. The range of dullness from 650 to 2000 grams would give us a whole new letter system of dullness.
In practical terms, anyone sharpening knives need only be concerned with the range from 0 to 475 grams. Edges duller than that require work.
The KN100 is designed to be accurate within +/- 10 grams of pressure. This standard is more than accurate enough for knife work.
I believe the KN100 is a very useful tool for a knife sharpener. It certinly gives the beginning sharpener a measurable, repeatable standard of what sharp is. It is flexible enough for expert sharpeners. For a sharpening business wishing to provide premium service at premium prices, the test results before and after could be posted on the customer's invoice.
The KN100 sells for $159 US. In Tormek terms, that is a little more than the three knife jigs and less than a replacement SG-250 grinding wheel. In my opinion, that is a lot of useful firepower for a bargain price.
Ken
Quote from: stevebot on June 30, 2015, 08:08:33 PM
I saved 10 test samples from the CATRA and I was impressed that they showed excellent correlation between the $160 KN-100 and the $12,000 CATRA.
How did they correlate with the opinion of the local chef?
For me, I see complications. Any meaningful judgement of sharpness depends on how well the knife cuts. And that in turn depends on what you're cutting. And then there's the issue of how well it cuts after you've been using it for a while. A knife that cuts very well for five minutes before its performance declines to mediocre may not be as desirable as a knife that cuts well enough and continues to do so for several hours of heavy use.
The factors that effect these performance issues are the edge angle and the tooth. Sometimes you want a larger edge angle, sometimes a smaller edge angle. Sometimes you want lots of tooth, sometimes you want very little. It all depends on what you're cutting and how much cutting you need to do.
A knife tester that allows for a slicing motion won't give the same results as one that doesn't. When we use knives sometimes we slice and sometimes we chop. I think it may be too subjective a thing to be measured.
Not everything that counts can be counted!
Quote from: stevebot on June 30, 2015, 08:08:33 PM
This spring I took part in a knife sharpening competition. We had use of two commercial testers plus the subjective opinion of a local chef. The results - 3 tests times 3 knives per sharpener - were overwhelming. I quite agree a simple test method is desirable.
Herman,
I agree that an initial sharpness measurement is not the full story of an edge's usefulness. This would apply whether the sharpness was tested with KN100, a thumbnail, a piece of paper, or a tomato.However, as stated in the quote, the competition also included being judged by the subjective opinion of a local chef.
I believe the KN100 allows the user the opportunity to measure the sharpness of a given edge at a given time with sufficient accuracy and repeatability. I suggest you download the instruction manual from the edgeonup.com website. If you have trouble downloading it with your browser, email them. They are working on the problem and will email you a pdf. I think you would find the more in depth details fascinating.
The KN100 can test much more than initial sharpness. The manual mentions the measurable difference after five 1/4" (6mm) cuts are made in a standard business card. It discusses the measurable difference after the knife sits overnight (due to minor oxidation). It discusses the measurable differences after using a strop and when using different grits.
I have noticed that some paper works better than other varieties for edge testing. Using one's thumbnail with repeatable accuracy seems scientifically iffy at best. I use these tests all the time as rough indicators. I also use the palm of my hand as a first test for fever. This indicator test is no substitute for a good thermometer.
I would expect an experienced sharpener to have a good knowledge of the effects of varying bevel angles and things like "tooth". I would also expect that sharpener to have a rudimentary knowledge of metalurgy and its effect of the keenness and durability of edges.
I believe the KN100 gives us a much more accurate starting point in being able to produce consistently sharp knife edges. It can also be used to track that sharpness throughout both the sharpening and use processes. It allows us to be able to repeat the process and to share the results meaningfully with others.
I also believe the KN100 is capable of much more in the hands of an experienced sharpener with a solid physics background.
Ken
Two years ago I prototyped a slicing tester that graphed sharpness along the blade length. It was 100% mechanical, no computer or load sensor, and was made from about $50 of common parts. It worked, but resolution was poor and it required a high resistence test sample to overcome the friction of the cheap slides I used. I intended to refine it, then along came the KN-100 BESS tester.
This year I was doing some difficult slicing and stumbled upon a quick and easy edge holding test method. Now that I am retired I plan to work on that idea - right after I finish the honey-do list and get my sharpening video into production.
I suggest taking early retirement to allow adequate time for the "honey do" list......
Ken
around 75 years should do it :-)
Hi, everyone. I've been lurking for a while. I first used a Tormek perhaps 7 years ago and I recently bought a second. I may need a third soon, as I develop my little part-time retirement business. It's a truly remarkable machine.
For the past few days, as I redevelop my sharpening chops, I've been playing with my newly-acquired KN-100 (thanks, Steve!). I have to say that it is proving extremely valuable in comparing knives in the "incoming" queue with the same implements after sharpening, and in comparing the results of various sharpening techniques and procedures.
I understand the reservations Herman has expressed (and the rather harsher criticism I read on Blade Forums), but I think that a quantifiable, repeatable way to measure edge sharpness (even if it is "only" a single-point push test) is a very useful tool for serious sharpeners.
~Doug
P.S. Like Ken, I spent a long time in the telecommunications world and I grew rather attached to accepted, communicable, measurement standards. Complaints about noisy circuits, for instance, were much more meaningful when accompanied by signal-to-noise measurements and references to agreed standards for the same.
Welcome to the forum, Doug. Thank for your comments in regard to the sharpness tester. I am sure it would be advantageous for comparison purposes.
I imagine some of us hate the thought of laying down that much money when we already know the knives we sharpen are sharp. I am not knocking the tester or those that are willing to lay down the money for one. As I mentioned previously, a person could fabricate a working unit.
Could it possibly be that I don't want to face a real test of sharpness? Surely not!? :o
Welcome to the active forum, Doug. It's nice to have another phoney aboard.
We live in a culture of measurements. One of the unfortunate words is "POTS" (plain old telephone service). The somewhat derogatory term does not do justice to the rather sophisticated set of service electric measurements to comply with the standards required by the regulating agencies. We need these standards in many areas because expertise is not universal. Elden, you have many years of sharpening experience and some high level training (You mention your Belsaw-Foley training.). What a beginner might consider "sharp" might not seem that way to someone of your experience.
What the BESS scale does is help level the playing field. It will not in itself make a beginner into an old hand. However, it will provide an objective, repeatable measurement of sharpness. I think you could pass a test of real sharpness, however, if it was me, I would do the initial tests where no one else would see them! :)
The KN100 costs $159 US. For those of us old enough to remember when a very usable second hand car could be had for a hundred dollars, that seems like a lot of money. In more recent times, my present car and former truck, both economy models purchased second hand, each cost more than my first house. Today one could purchase the KN100 with a Tormek Small Knife Holder for about the same cost as a replacement SG-250. Unfortunately, wage increases have been flat for many years.
I do not believe everyone needs the equipment to test edge sharpness. The tried and true methods of cutting paper, thumbnail testing, and arm hair shaving work as well as they ever did. What has changed is the level of possible sharpness testing. The KN100 makes this not only possible, but practical for many sharpeners.
Ken
Thanks, both of you, for the friendly welcome.
Elden, I certainly understand that not everyone who sharpens edges needs or wants an edge tester. Of course you know what is and isn't sharp, and you know a lot more than that about edges. On the other hand, I expect you know a lot of folks who have no bloody idea ;^) what "sharp" means -- and they want "sharp" knives even though they haven't a clue.
I think it's possible that the BESS scale may help in educating those people and in comparing knife edges, at least to some extent.
This morning I read through the EST-KN100 Edge Sharpness Tester operating instruction manual. It is available to be read online at:
http://www.edgeonup.com/eou_web_pagelarge_008.htm
Suffice it to say, I am very impressed. The product sounds great, but the manual is an excellent work. There is a little bit of redundancy in cautionary statements, but they are validly pertinent.
The section "A little more on wire edge removal" was extremely interesting. It starts on page 41 of the manual. Yes you read that correctly, PAGE 41! There are 46 pages in total that are easily understood.
No, I have not bought one. However, I am very impressed. Thanks for bringing the EST-KN100 to our attention, Steve B.
Quote from: kb0rvo on July 11, 2015, 07:08:33 PM
This morning I read through the EST-KN100 Edge Sharpness Tester operating instruction manual. It is available to be read online at:
http://www.edgeonup.com/eou_web_pagelarge_008.htm
Suffice it to say, I am very impressed. The product sounds great, but the manual is an excellent work. There is a little bit of redundancy in cautionary statements, but they are validly pertinent.
The section "A little more on wire edge removal" was extremely interesting. It starts on page 41 of the manual. Yes you read that correctly, PAGE 41! There are 46 pages in total that are easily understood.
No, I have not bought one. However, I am very impressed. Thanks for bringing it to our attention, Steve B.
I have found the page 41 also very interesting :), especially the term
metal memory.
I know the term
memory metal, which is an alloy with a shape memory, which returns an object to its original shape, when heated (an example from the nanoworld is Nitinol = nickel-titanium).
But Steve B. coined the term
metal memory to describe the situation when the stropped edge returns to its original (pre-stropped) geometry after several hours.
Really interesting mention and for me worth of further investigations.
Jan
I agree, Jan. This sounds like an interesting topic.
Ken
I'm glad others are also finding the possibilities of edge measurement interesting.
As for metal memory, I've been experimenting recently with a bunch of sets of cheap, stainless kitchen knives that were bought years ago for practice. I'd almost swear that some of them have "recurring burr" syndrome.
Of course, I could be confused. ;^)
Likely it's a brittle edge breaking off. Try a more blunt angle.
I bought a couple of extremely cheap pocket knives a couple years ago. Impossible to sharpen. If I made the edge angle extremely blunt I could prevent the edge from breaking off. Of course with an angle that blunt they aren't good for much other than loaning to neighbors. :)
I started this topic by describing how I had tested the edges of my two paring knives with the KN100 edge tester. The less sharp edge tested 625 grams to break the testing media. The manufacturer rates that in the range of needing to be sharpened. Not terrible, but not good.
I have been experimenting with using valve grinding compound with the leather honing wheel. It does not leave as polished a surface as the Tormek compound, however, it cuts faster. I did some VGC honing with the paring knife. No work with the grinding wheel or steel. Just VGC honing.
I have a premeasured 375 gram weight. (It is a peanut butter jar partially filled with BBs turned upside down so that the flat lid sits on the KN100.) 375 grams is the manufacturer's top range (375-475 grams) for "factory sharp". A good sharpener can easily best that, however, it is a good starting point. The knife cut the media at that weight. I did not do any more precise testing.
I should state that I have two leather honing wheels. I do not think it is a good idea to use different grits with the same leather wheel. I can interchange the two wheels in seconds.
Using just the VGC leather wheel as a quick and dirty touch up seems of limited value to me. However, I do think it has potential when used with the SG grinding wheel in its coarse state. This could be useful for anyone doing a lot of knife sharpening, such as at farmer's markets. If the technique works well, it would eliminate the time needed to regrade the stone to fine. The finished edge is not as highly polished as when the knife is sharpened with both grits of wheel and the Tormek honing compound. For slicing knives this might actually be an advantage, as we like to add tooth to the edge.
I would welcome comments from other members who work more withknives than I do.
Ken
Quote from: Herman Trivilino on July 16, 2015, 04:18:51 PM
Likely it's a brittle edge breaking off. Try a more blunt angle.
It may be, but it really seemed as if a burr were reappearing on a honed edge. Maybe the coffee is too strong.
Around here, I couldn't even give these knives away (no recognized and desirable brand names!) and, if I could, it would ruin my reputation forever. They're really terrible. Maybe they could be re-purposed for icing cakes and other jobs where edges aren't really required.
Doug, be nice.....Herman never said that he liked the neighbors..........
Ken
Here is a video I made about knife sharpness testing.
https://youtu.be/rMi9TyOXUcg
Quote from: Ken S on July 17, 2015, 11:40:20 PM
Doug, be nice.....Herman never said that he liked the neighbors........
;^)
Quote from: SharpOp on July 16, 2015, 06:56:23 AM
As for metal memory, I've been experimenting recently with a bunch of sets of cheap, stainless kitchen knives that were bought years ago for practice. I'd almost swear that some of them have "recurring burr" syndrome.
In my thinking, the physical reason for the "metal memory" or "recurring burr" syndrome may be
the residual stress, which remains in the steel near the cutting edge after the sharpening process.
It is not fully clear to me, why the residual stress occurs, but a small edge asymmetry may be one of possible mechanisms.
The residual stress can be relieved by suitable thermal or mechanical trigger. Because the stropped cutting edge is often in a state of fragile equilibrium a tiny trigger may be sufficient.
Jan
What about testers that measure the ability to stay sharp?
There are several ways to test a knife for sharpness but I'm more interested in ways to measure the steels ability to withstand wear.
If the knife is sharp or not is more dependent of the sharpener, the ability to keep the sharpness over time is more up to the manufacturer of the steel and the blade.
There is a British organisation called Catra that has a quite nice machine that measures how many paper strips the knife can cut over a series of strokes. The paper is pushed with a pre determined force against the edge.
I'm looking for something like that but a bit more simple, so I can have it in my shop or bring it when I lecture.
Have you seen something that can do the job?
Magnus, you have asked the right question at the right time. Edge On Up (www.edgeonup.com) has just introduced a lineup of edge testers. I just purchased the HT-50 model. The new HT-50 model is substantially easier to use than the KN-100 model I have used for a year. The website has a series of excellent short videos explaning setup and operation.
The HT-50 is quite portable and quick to use in the field. I think it would be an excellent choice for you when traveling.
In one of the videos Mike Brubacher begins with the test reading for a brand new double edge razor blade fresh from the factory wrapper. He then makes only one small cut cutting through only half of the razor blade wrapping paper only one time. The difference in sharpness measurements was impressive.
All of the Edge On Up edge testers utilize the BESS standard. (Brubacher Edge Sharpness Scale) This is a scientific but simple standard which is consistent and repeatable. Questions you might receive from knife customers in Australia, the Czech Republic, the UK, the US or even Sweden, would be in a common "language" and repeatable.
Check out www.edgeonup.com. You will find Mike very helpful.
Ken
I visited Mike Brubacher of Edge On Up a few weeks ago and one of the things we discussed was an edge retention tester. I hope that between the two of us we will have a prototype to show at the 2017 Sharpeners Report convention. Mike has experience with mechanics and load cells. I built a prototype tester that slices and records the force vs the position on the blade. The retention tester will be somewhere in between - cutting at only one point on the blade but recording the force as a function of the amount of material cut.
There are a lot of questions to be answered:
What media to cut?
What to do about side friction?
When is a knife dull beyond use?
Which is better? Blade A starts at 200 and dulls to 400 in 10 ft. Blade B that starts at 300 and dulls to 400 in 15 ft. Blade C starts at 400 but cuts 20 ft before it dulls to 425.
Steve, I think you have to find some formula for the edge retention. For example, it can be defined by the ratio of the length of cut vs drop in sharpness.
Then:
edge retention for blade A = 10 / (400 – 200) = 0.05
edge retention for blade B = 15 / (400 – 300) = 0.15
edge retention for blade C = 20 / (425 – 400) = 0.80
Following this definition the edge retention of the blade C is the best. :)
The proposed formula, however, favors blades with low initial sharpness (blade C). This should be corrected by suitable additional term or formula modification. ;)
Jan
Steve, the modified formula for edge retention could read:
edge retention = length of cut * initial sharpness / final sharpness
For your example we get:
Blade A = 10 * 200 / 400 = 5.0
Blade B = 15 * 300 / 400 = 11.3
Blade C = 20 * 400 / 425 = 18.8
So, also based on the modified formula, the edge retention is the best for the blade C. The modified formula does not favor blades with low initial sharpness as the previous one. :)
Jan
The fact that you measure the sharpness on one single point makes me doubt this method a bit.
You can take a sharp knife and bounce it on your fingers without cutting your self but if you would move the knife just a bit you would immediately cut yourself quite badly. Do you see what I mean?
Anago in New Zeeland has a really nice tester as well that tests the sharpness over the whole edge in one sweep, sadly it's not very portable.
http://www.anago.co.nz/knife-sharpness-tester/
But neither this tester measures ability to withstand wear, unless you repeat the test over and over.
Perhaps it's back to paper cutting again...
//magnus
ANAGO tester is in the CATRA price range, both 100 times over the Brubacher's.
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. :)
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.
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
Quote from: brettgrant99 on April 09, 2016, 12:30:23 AM
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 (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.
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
Dear Ken, Mendeleev wasn't first to notice elements periodicity, but who cares about those first?
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
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. :D
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
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
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
Jan,
I have always interpreted your comments as encouragement rather than criticism. As one of our members says, "One man sharpens another".
Ken
Touché, Ken! :)
Jan
:)
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
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
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
Quote from: Ken S on April 12, 2016, 04:05:04 AM
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
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
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. :)
(http://img21.rajce.idnes.cz/d2102/11/11771/11771137_37021e568ec44478b9ce7dc74d286378/images/FROGS_LEG.jpg?ver=0)
Jan
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.
Interesting ideas, Herman.
Ken
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
Quote from: Ken S on April 12, 2016, 10:42:54 AM
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
Quote from: Jan on April 12, 2016, 11:01:49 AM
...
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
Quote from: Herman Trivilino on April 13, 2016, 05:40:29 AM
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.
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.
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
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.
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
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
Fascinating post, Grepper.
I think a Catra machine should be part of the kit of every serious Compleat sharpener. Older members of the forum may have enough equity in their homes to get a home equity loan for one. Steve has mentioned the Catra in conversation. I don't recall the exact price, but several thousand US dollars sounds familiar. Having one would give you significant bragging rights at the farmers' market!
On a more practical level, the basic Edge On Up tester may be purchased complete for seventy nine US dollars. The more sophisticated PT-50 tester is only one hundred thirty nine dollars. Either of these testers will allow a Tormek user to test his edges with good accuracy. BESS may not yet be the accepted standard for the engineering/scientific community. I am quite comfortable with a measurement which is understandable, consistent and repeatable with the sharpening community.
Among my collection of machinist tools, I have a kit of surface samples. These are several small pieces of steel ground to different known and accepted degrees of surface smoothness. These are held up to a machined piece to see if it is of matching smoothness to the blueprint. The engineer determines the smoothness required. Matching the smoothness is important because the product must both meet the needs and be cost efficient. Spending the extra production time to produce parts machined beyond their needs adds to the cost, but not to the practical quality. Size tolerances are the same way. Thread clearance tolerances depend on the application. Working to closer tolerance than is necessary adds to the cost without necessarily adding to quality beyond the machinist's pride.
While we seem to enjoy cutting paper and shaving our arm hairs, BESS gives us a more organized, consistent method of measuring practical sharpness at a price the average sharpener can afford. BESS has the same range of utility as the kenjig. The kenjig is designed both for the busy farmers' market sharpener who must work efficiently and has great skill AND for the beginner who is learning. BESS can also do both. It provides the skilled sharpener with quick repeatable data demonstrating the sharpness of his edges. It can also assist the very beginner sharpener (what Charles Hayward, the famous British woodworker, would call "the veriest tyro") with a readily mastered method of gaging his progress. In my opinion, that's a very useful niche.
Ken
Quote from: Jan on April 13, 2016, 08:22:54 PM
Each BESS unit corresponds to 0.01N (1 centinewton) of applied force.
Ahhh ... Thanks for that. All I needed to know. So speaking properly, it's a force not a pressure.
Yes Herman you are correct, the measured quantity is a force, however the pressure/stress at the edge is of crucial importance. ;)
At the initial stage the edge elastically deflects the surface of the test media. Then, at a critical contact stress, the edge penetrates the surface of the test media. The force necessary to reach the critical contact stress is a measure of sharpness.
When the knife edge is blunt, then the elastic deflection is much greater and the critical stress for the media penetration may or may not be reached. This depends on the size of the applied force.
Jan
Quote from: Ken S on April 14, 2016, 11:35:49 AM
Fascinating post, Grepper.
I think a Catra machine should be part of the kit of every serious Compleat sharpener. Older members of the forum may have enough equity in their homes to get a home equity loan for one.
Uhm, yeah ???
Define serious! Define compleat, then complete?
Is this a commercial sharpener? High end hobbiest with an ego, or what?
What is the target audience they cater to? Does the target audience understand the scale or what the measurements reflect? Does the customer tell them how to sharpen? (I want it at this scale, because I use it for x aka the toothy tomato argument)
One of us, who is middle aged, with a paid off home, thinks this is more of an ego trip, that provides seriously questionable value, at best. At worst, it is you trying to get into our pockets and spend our money (and wondering if you have stock in the company)!
Lighten up, amigo. I was being facetious. "Compleat" usually refers to someone with an irrational sense of completness. In reply one of this topic, Steve states a price of $12,000 US for a Catra. I am not questioning the value of a Catra. If this fits your ego and wallet, go for it! Both my ego and wallet are considerably smaller. My curiosity and wallet can swing the hundred and forty dollars for an Edge On Up PT-50, but certainlu not a Catra.
Ken
One problem with just text, and part of the reason smiley's were invented, it is SO hard to tell someones tone, just by what they right. IMHE, it is told by what is going on to the reader and the mood they are in. (in my case, just having someone recently "oh, lets spend your money, you won't mind")
The money in the range you say is affordable, to me would be better spent on Steve's video's then a tester at this point, however lots of expenses are currently happening and delaying "fun" time.
SADW,
You are correct; my humor can sometimes be too subtle. Sorry about that. :-\
I agree. I would make Steve's Sharpening School DVD a priority purchase. Training first. An edge tester can follow. By the way, Steve's video has the best section I have seen on conventional edge testing (thumbnail and various paper tricks).
I am gradually adjusting to the smiley faces.
Ken
There are two lesser known sharpness tests on the video.
Just a reminder, that is on section that is available free at
https://www.youtube.com/watch?v=rzWdpjyDZKM
I do not often test a customers knives but rely on a consistent method to give consistent results. Some would say ritualistic. But yesterday a friend brought 4 knives over and I had the time, so I tested. When I saw the results of my regular sharpening I decided to add an extra stropping step.
As delivered BESS 600 to 1000 grams
First sharpening BESS 250 to 300 grams
Second sharpening BESS 175 to 225 grams
For reference, a new double edge razor BESS 50 grams
The Rabbi's knife, sharpened by me, BESS 100 grams
For the curious, this differs from my regular sharpening as follows:
German edges - 18 primary, 24 secondary at fine ceramic grit
Above, same plus a stropping
Japanese knives - 15 primary, stropped; as was the Rabbi's knife.
Interesting, Steve. Would you elaborate about the first and second sharpenings?
How would the rabbi's knife compare with a scalpel?
I have been kicking around an idea in the back of my head. I want to try using the SG-200 standard wheel of my T4 followed by the T7 with the SJ-250 Japanese wheel. I believe the radius difference in the wheels would give a similar primary and secondary bevel effect, the finer wheel being set to only polish the every edge, not the entire bevel. Thoughts?
Ken
Quote from: Ken S on May 08, 2016, 03:44:50 PM
I have been kicking around an idea in the back of my head. I want to try using the SG-200 standard wheel of my T4 followed by the T7 with the SJ-250 Japanese wheel. I believe the radius difference in the wheels would give a similar primary and secondary bevel effect, the finer wheel being set to only polish the every edge, not the entire bevel. Thoughts?
Ken
Ken, you are very inventive! :)
All will depend on the edge angle setting for the SG-200 and the edge angle setting for the SJ-250 grindstone. The radius difference in the grindstones itself cannot be reason for grinding primary and secondary bevel.
Please let me know the result of your experiment.
Jan
Jan,
Thanks for your encouragement. So many times my "inventiveness" is merely utilizing existing ideas in different ways. The kenjig is the combination of a twist on the wooden spacer block method from the handbook and the projection stops as seen in the TTS-100. The idea of combining the T4 and T7 to grind a bevel and polish just the extreme edge is one hundred percent lifted from Steve's Sharpening School DVD.
I will post the results. I am getting quite a backlog of projects. I have long believed that the Tormek is a versatile machine capable of many variations in technique.
I will have to actually grind to absorb the effect of different radii.
Ken
Quote from: Ken S on May 08, 2016, 03:44:50 PM
I want to try using the SG-200 standard wheel of my T4 followed by the T7 with the SJ-250 Japanese wheel. I believe the radius difference in the wheels would give a similar primary and secondary bevel effect, the finer wheel being set to only polish the every edge, not the entire bevel. Thoughts?
Ken
I've used the SJ250 (250mm) after using the very little worn SG250 (245mm) and you can already see that the SJ250 would leave the middle of the cutting edge untouched. With higher pressure it will "clean" all the edge.
So on first thought using the SG200 first IMO would be to big different. On second thought it could be a nice effect and worth trying.
As for the KN-100 I think it's getting too academic for chefs knifes (my working volume), and I, by practice always test with thin newspaper page. It gives me 2 indications.
1. If there is still some burr (even microscopic) somewhere along the edge.
2. I can feel how sharp the edge is by feeling how easy and smooth it cuts the paper.
Many times you can see ppl cutting printers paper with fast and forceful movement. It is by far more edge sharpness proof to do it slowly and controlled. Anyway customers are getting very impressed by the fast cutting movements to show how sharp the knives are after the sharpening session. But they get more impressed doing it slowly and with waves cut on the paper.
Interesting thoughts, WolfY. I suspect you may be right about the radius difference, however, I will run the test to verify.
I agree the KN-100 is a bit academic for many sharpeners. However, the two latest edgeonup.com models are much more user friendly and practical for in the field. Your newspaper tests sound very useful, although, if I wasn't a very good sharpener, I would prefer heavy paper. It can mask a lot of dullness while still impressing the crowds!
Ken
Quote from: Ken S on May 13, 2016, 03:16:24 AM
Your newspaper tests sound very useful, although, if I wasn't a very good sharpener, I would prefer heavy paper. It can mask a lot of dullness while still impressing the crowds!
As we are on Tormek forum, "if you were not a very good sharpener" you are not using Tormek, or have to practice little to become a good sharpener as you have the right tools. (not you in person ;) )
I have the WE Gen3 Pro sharpener here as some clients asked for it. On 1000 grit you can't even get close to sharpness and sharpening time/result with it, compared to the Tormek. After they saw that, they got the Tormek. Also price wise it's unbeatable in favor to Tormek.
IMHO, WE have lots of errors that ppl don't know and not worth the money at all. Works OK on small pocket knifes and nice when compared to freehand sharpening on japanese stones. Other wise time and energy consuming with very bad price/result/time ratio.
This VDO shows a knife that was in condition that you couldn't cut yourself and the tip was bent after faling on the floor.
https://www.facebook.com/ultrasharpisrael/videos
Quote from: WolfY on May 13, 2016, 01:41:48 AM
I've used the SJ250 (250mm) after using the very little worn SG250 (245mm) and you can already see that the SJ250 would leave the middle of the cutting edge untouched. With higher pressure it will "clean" all the edge.
So on first thought using the SG200 first IMO would be to big different. On second thought it could be a nice effect and worth trying.
WolfY, thanks for sharing your interesting results. :)
I am very surprised, that you were able to observe untouched cutting edge in the middle of the bevel sharpened using SG-250 with 245 mm diameter.
When you have set a bevel angle of 15.0
o for SG250 (245mm) and used the same position of the USB for the SJ250 (250mm) than you should sharpen a secondary bevel of circa 15.4
o. It is hardly visible difference.
Possible explanation for the untouched part of the cutting edge could be slightly larger hollow depth for the smaller SG250 (245mm) grindstone then for the larger SG250 (245mm) grindstone. But this difference is really microscopic.
As you mentioned, pressure differences during sharpening could also influence the result.
Jan
Which BESS sharpness tester are you guys currently using?
My favorite is the PT-50. I have used all three models, and like all three. I chose to purchase the PT-50, which probably speaks louder than word.
I like the increased accuracy and it seems easier to use (just my opinion, I could be happy with any of the three)
Ken
Well, this was a long read.
Anyways, I too use the BESS method. Though not an ISO, ASME, ASTM, etc. standard, it is a fantastic tool. I have been collecting data with it and my whetstones (having newly acquired a T-7 have not had experience enough to collect data yet for the Tormek). I am working on a graph of "BESS mass [g]" vs "sharpening medium [µm]". The BESS system is great for this because you really only need the independent variable to be standardized of sorts. Granted, the sharpening/honing grit is only as good as the operator.
In an effort to tie into the original question of "how sharp is sharp", I move to offer that the answer is relative to the task. In my perfectionist mind, nothing is sharp unless you get cut just by looking at it (see most any Japanese sharpness story). I have trouble stopping when I take on a set of knives to sharpen, I would call it a problem if I was not proud of my work. How could I not produce an edge that I am not proud of? However, this once again leaves us with the relative sharpness of an edge. To me, sharp happens when I run out of honing paste that is smaller than what I am currently using; as you can imagine, this is not practical. That is why I am so dedicated to producing this graphical representation of "sharpness vs µm".
I would love to help answer any questions with this regard. My current items to question are as follows:
What µm medium is the minimum requirement to break the BESS "sharp cutlery" requirement?
What grit is the apex most prominent?
How does this method compare across steel types?
how does this method compare across blade types/thicknesses?
Sharpness of knife upkeep (steeling vs stropping)?
As an aside, I would like to take magnified photographs of each sharpness at multiple blade points to try to qualify the "look" of a blade with sharpness. Perhaps a diagnostic visual test. Perhaps an arbitrary method, but say... 2 visible blade imperfections per inch qualifies the blade to the "not sharp" category.
I also want to test this on my personal knives with longevity and durability. There is no standard for when someone needs to resharpen their knives, just hone often enough and you are fine for 6-12 months. I don't like this. Perhaps I could have my neighbors contribute to the study and let me take BESS scale measurements and record them?
OORRRRR, I may just be taking this too seriously and sharp happens when you can cut a tomato. ;D
Jon
Interesting experiment, Yargnoj. Another variable to consider is the edge angle. At smaller angles the steel gets thinner faster as you approach the edge. At some point you will run into a limit due to the fact that the steel is too thin to hold an edge. You may be able to measure a sharper edge, but as soon as that edge is used to cut something it crumbles and thus gets very dull very fast. A knife so sharpened would be a disappointment to use.
Ah yes!
Perhaps there is a correlation here as well. I wonder if it would be linear or not? In my mind, BESS sharpness would asymptotically approach an angle of incidence where the edge first becomes 'sharp'. Perhaps this would be 90°. I would expect this curve to follow a quadratic function, thus making it difficult to choose the best angle to sharpen at. The observation of infinitesimally small edge, though being sharp, and its lack of durability would half to play an important factor. Perhaps if there was a systematic approach to dulling a knife consistently, at a small rate; a before and after "snapshot" would be useful.
The graph of inverse durability vs angle and sharpness vs angle, when charted together, may yield a max or min that could show the best combination of the three variables.
I believe my time spent per knife sharpening has just doubled to accommodate data collection.
"The graph of inverse durability vs angle and sharpness vs angle, when charted together, may yield a max or min that could show the best combination of the three variables."
Jon-
Well..., that would be very cool to see! I for one definitely encourage you to do that.
Please do it for about RHC 52, RHC 58 and RHC 62. Measure the sharpness, then chop up 100 carrots with each blade, take another sharpness measurement and do another set of graphs.
That real world testing would be extremely informative and well worth your effort! :)
Quote from: yargnoj on May 20, 2016, 04:26:47 PM
... I am working on a graph of "BESS mass [g]" vs "sharpening medium [µm]". The BESS system is great for this because you really only need the independent variable to be standardized of sorts.
Jon
Generally, the resultant edge is finer than the sharpening grain size.
But
Jon, I honestly cannot understand how this can be measured for the continuum of sharpening mediae by BESS tester. With sharpening media coarser than JIS #6000 the ragged burr will be severing the test thread rather than the edge, and this reading cannot tell much.
e.g. my repeated testing of an unhoned edge after #220 Tormek grindwheel gives 130 units variance on BESS, you cannot rely on that; while method of de-burring you may use will effect the BESS reading...
Quote from: wootz on May 21, 2016, 01:21:28 PM
Generally, the resultant edge is finer than the sharpening grain size.
Wow! That's interesting. Do you know how wide a knife edge would be after sharpening with the SG finely graded? A typical bevel angle is around 15° or 20° making the edge angle around 30° to 40°.
The steel used in knives varies greatly in composition, but I wonder if something can be quantified. I refer to the microscopic structures, whatever they might be called. These would be the grains of steel, for lack of a better term. Do they exist in a form where their size can be measured?
The size of steel grains can range from nanometres to millimetres depending mainly on cooling rate. Rapid cooling generates smaller grains and strengthens a material.
Typical grain size may be ~50 000 atomic diameters which is more than 10 micrometres. Please take it with a big reserve, it is a very rough estimation.
Jan
Quote from: Herman Trivilino on May 21, 2016, 07:35:18 PM
Quote from: wootz on May 21, 2016, 01:21:28 PM
Generally, the resultant edge is finer than the sharpening grain size.
Wow! That's interesting. Do you know how wide a knife edge would be after sharpening with the SG finely graded?
Easy, if you have a BESS tester.
1 unit on BESS scale roughly = 0.01 micron of the edge width (the correlation is practically straightforward in the lower range of the scale form 0 up to 500).
A JIS #1000 stone has grain size of 16 micron, so the best edge you can get will be somewhere around 10 microns.
Obviously, after #1000 stone some de-burring must be done, and the method of honing you use will effect the BESS value.
E.g. if after the Tormek #800-1000 grindwheel I hone on a paper wheel with 0.5 micron diamond paste, the final BESS reading is about 80, i.e. edge under 1 micron .
As to what can be achieved by honing on the Tormek honing wheel with the Tormek honing paste, if I remember right Ken was planning to test this...
Quote from: Herman Trivilino on May 21, 2016, 07:35:18 PM
Quote from: wootz on May 21, 2016, 01:21:28 PM
Generally, the resultant edge is finer than the sharpening grain size.
The steel used in knives varies greatly in composition, but I wonder if something can be quantified. I refer to the microscopic structures, whatever they might be called. These would be the grains of steel, for lack of a better term. Do they exist in a form where their size can be measured?
Electron microscope.
But then, as with your evidence post, you will get averages across the knives that you submit to the microscope. You may find a more consistent batch, but what you choose to use out of that batch, may or may not be the same.
:)
... and for those who don't have access to the scanning electron microscope, BESS reading can give some idea of the edge thickness...
Wootz, I would like to ask you what is the argument to support your statement that "1 unit on BESS scale roughly = 0.01 micron of the edge width"? :-\
Jan
Quote from: Jan on May 23, 2016, 02:08:31 PM
Wootz, I would like to ask you what is the argument to support your statement that "1 unit on BESS scale roughly = 0.01 micron of the edge width"? :-\
Jan
Unpublished data from Mike.
I couldn't stop thinking that one unit on BESS may correspond to 0.01 micron edge. I gathered a number of observations, and wrote to Mike, and he replied with data that support this correlation.
There is little theory behind this, but many facts that make it practically useful.
This straightforward correlation gives BESS clear advantage over other sharpness scales.
Thanks for mentioning the source, I was afraid I am missing something.
Jan
P.S.: Might be of your interest: "Can you sharpen a razor blade to a 1 atom width blade?".
https://www.reddit.com/r/askscience/comments/1oboky/can_you_sharpen_a_razor_blade_to_a_1_atom_width/ (https://www.reddit.com/r/askscience/comments/1oboky/can_you_sharpen_a_razor_blade_to_a_1_atom_width/)
I have been interested in chemical sharpening for a long time. It is great for sharpening a point but I have found no way to apply it to an edge. Chemical sharpening is used in production of fish hooks.
A friend is in the physics dept of a local university and has access to various exotic techniques like electron beam honing and deposition of a single atom layer of diamond but again, no practical way to apply it to everyday knives.
The only chemical sharpening I was aware of, has to do with files, and my understanding is, restoration attempts.
As Steve confirms, for the time being, the chemical sharpening to 1-atom edge has no practical application in everyday sharpener's life.
The single atom tungsten tip is high-tech scientific tool only. But it is surely not a final stage, there are much smaller particles in the micro world! ;)
Jan