03-15-2017, 11:21 AM (This post was last modified: 03-15-2017, 02:06 PM by Jan.)
Hello Mike, hello everybody. My name is Johanka and I am a secondary school student. I am using the account of my grandfather. I am not a knife-sharpener but last year I have learned how the BESS scale works. I will post here how it happened.
As I learned in physics about force I needed to know what is the difference between weight and mass. My grandfather Jan explained it to me on the example of the BESS scale. He told me that Mike measures edge sharpness by the size of force which is necessary to cut the test medium. Mike uses a digital scale which measures force but calculates and displays mass in grams.
We have built a simple sharpness tester from Lego. On our kitchen scale we can read how many grams would create a weight which would be able to cut an elastic band. Our kitchen scale weights up to 5000 grams and so I think it could measure even the "sharpness" of a completely dull axe.
Of course you are correct! I know that you are the best knife sharpener in the Czech Republic and your grandfather is the second best. I should have known that someone as bright as you would invent a better edge sharpness tester than we did and costs less as well. Its also much more colorful and pleasing to the eye.
Your instrument demonstrates perfectly the principle of edge sharpness testing and our S=F/A equation. Of course your grandfather was very helpful with this equation as well. This equation applies not only to BESS Test Media but to many other medias as well. Your rubber bands are an excellent example. A new axe blade (often referred to as an "axe bit" here in the USA) will typically measure between 900 and 1400 on the BESS. It is a good example of how different tools are sharpened to different levels and according to the application they are intended for. It is difficult for me to say what measurement you will get when you test an axe with your instrument because I have no experience with rubber bands as a test medium. I would very much be interested in the reading you do get though.
Please don't put your instrument into production before you graduate from secondary school. I have a few more of my own instruments here that I would like to sell before you do. Please stay in touch. Your writings are always smart and interesting.
Thank you for your kind words, Mike! Do not worry about my Lego edge tester production! May be you have noticed that our Lego knife-sharpeners have real small knives made of stainless steel. The boy is grinding while the girl is stropping.
Yes, I see that now and thank you for drawing those two details to my attention. That is really neat! I'm happy to hear that I will still be in business for at least a little while longer. On the more serious side and as you find time, I would be interested in some of your test numbers for knives using rubber bands. Let's call it the "Johanka Scale".
Well I hadn't even thought of that grepper but you're right. This young lady is killing me! Bernie with BESSU is going to be in the office here this afternoon. I'll have to tell him that he has competition now.
(03-16-2017, 09:27 AM)Mike Brubacher Wrote: On the more serious side and as you find time, I would be interested in some of your test numbers for knives using rubber bands. Let's call it the "Johanka Scale".
Mike, it would be very nice to have own sharpness scale but during the school year it would be difficult for me to deal with it. Even more in physics we have moved from mechanics to electricity and magnetism.
It would be much easier for me now to discover something that deals with magnets. I am wondering if a magnetic knife cuts better or lasts longer sharp than a normal knife.
Holy smokes Johanka you're putting me through my paces now! Just when I had breathed a sigh of relief upon finding out there will be no JESS scale or Johanka edge tester on the market you ask me a question like this one. I am hoping that we are on the same page with your question in that you are asking if a magnetized steel blade might have some advantage over a non-magnetized steel blade with regard to edge retention and/or sharpness. I can promise you that there are people on this Exchange that are better qualified to answer that question than I but I will give it my best attempt. I hope that you are not talking about a magnetic knife because I don't know what that is but I haven't read the latest edition of Popular Science Magazine either. So here goes -
I have heard from time to time that some people have said that magnetizing a knife blade will lend to its strength. This theory holds forth, as I seen it proposed, that the individual molecular structure of the steel is "realigned" in a manner that strengthens the steel. My understanding of knife steel is this and I borrow, in part, from one of our technical documents that can be found on the Edge On Up web site.
" There is no "steel molecule". Steel can be described as a "solid solution". It is a subtype of chemical mixtures that involve at least two or more molecules in a solid state. These molecules combine to form a single substance "steel".
Once steel hardens the alloy becomes a crystalline structure, not molecular, so there are no molecules to realign. If I've missed the intent of your question Johanka I apologize and if I am misinformed on the subject then I expect the balance of the Exchange to bale in here and set me straight so that this young lady doesn't proceed through life with one segment of her memory banks filled with faulty information.
03-17-2017, 03:14 AM (This post was last modified: 03-17-2017, 08:02 AM by Jan.)
(03-16-2017, 04:07 PM)Mike Brubacher Wrote: I am hoping that we are on the same page with your question in that you are asking if a magnetized steel blade might have some advantage over a non-magnetized steel blade with regard to edge retention and/or sharpness.
Mike, you have perfectly formulated the tricky question!
Only a few substances are ferromagnetic (strong magnets); the most common are iron and nickel and their alloys. Physics tell us that the magnetic moments of iron atoms stick together and form so called magnetic domains which can be observed with a special microscope.
When iron/steel is exposed to a magnetic field the domain boundaries oriented with the external magnetic field grow. When the magnetising field is removed the domains may not return to the unmagnetised state. Above some temperature, called Curie point, iron loses its ferromagnetic properties.
In my understanding there is no doubt that on the microscopic level they are structural differences between magnetised and non-magnetised knife blade. The question is if those changes alter steel mechanical properties in a measurable way.
Make no mistake Jan, I was fully aware of the fact that Johanka didn't need to send her question off to the BESS Exchange in order to receive an answer. She simply needed to pay her grandpa a visit. I see though, now from your response, that her question was actually based on physical principles that are one or two planes above the level I answered from. I should have known that would be the case.
This is all very good stuff and the sort of thing that we are proud to have appear on the pages of the BESS Exchange. Thank you and a big thank you to Johanka as well!
JESS? 