This is concerned with normal, judicious blade sharpening with something like a Kally.
I’m in no way intending any declaration of fact, but rather, expressing what I think is going on and why. I’m hoping others with chime in with evidence or suggestions pro or con. It’s an exploration of issues rather than a collection of conclusions.
I’m going the preface this with the phrase “for all intents and practical purposes”. Admittedly, there are specific applications where, for example, a possible 10% difference may be significant. I only add this because this about general knife sharpening and I wish to avoid becoming mired in minutia.
I may be right or I may be wrong. But, I hope to say it in such a convincing way that even if you think I’m wrong, you will have to at least think I might be right. (That might be paraphrased from something Bob Dylan said.)
That said, IMHO, evidence so far presented indicates that:
Judicious sharpening with a Kally does not heat the blade anyway near enough to impact performance.
Q: How do you know there is not flash molecular level heating at the very apex of the edge?
A: I don’t and probably never will. And, for all intents and practical purposes, I think it to be irrelevant. Even if there is heating, it is an extremely ephemeral event both in heating and cooling. Neither heating nor cooling is sustained long enough to anneal or temper hardened steel.
Q: Assume there is super heating of the surface at the apex, could the super heating and rapid cooling actually harden the surface leaving soft metal just beneath?
A: Like a chocolate chip cookie? Do you mean like crispy on the outside and chewy on the inside? Who knows? Who cares? I guess maybe it’s possible at the molecular level, but again irrelevant. If indeed something like occurs, any ramification at the apex is so insignificant that it would be undetectable whilst chopping carrots or SET testing. While intellectually entertaining, I think this line of thinking is getting lost in minutia and missing the forest for the trees.
Q: Have you seen evidence supporting that belt grinding significantly impacts edge hardness or performance?
A: Yes. But it is very scant. Mr. KG presented evidence supporting the possibility that powered sharpening may impact edge performance in some circumstances. However, and I will discuss this shortly, that for all intents and practical purposes, the bulk of evidence I’ve seen so far is indicative to the contrary.
Q: Does harder steel, say, RHC 60, perform better and last longer than RHC 52?
A: Maybe. A little. Both EOU SET testing and Mr. KG presented data that indicates that in some cases there may be slightly better edge retention. However, this data is neither generalized nor conclusive and definitely not the case in most circumstances. Furthermore, there are disadvantages to harder steel such as difficulty sharpening and chipping that may overweigh any possible advantage. Moreover, in some of the EOU SET tests, softer steel rolled less than harder steel.
Mr. Reich astutely noted that all knives are ground sharp in the first place. I saw a video of the knives being sharpened at, if memory serves correctly, (correct me if I’m mistaken) the Hinckel factory. They were sharpening on large, dry grinding wheels. It’s not as if mother knife gave birth to baby knives and they are born, they are ground sharp.
Notes:
EOU SET testing data indicates that that in general there is no significant difference in resistance to rolling between HRC 52 and harder steel. Even if edge softening occurs as the result of sharpening, it is mitigated by the data indicating that as far as range of hardness used in knife steel there is little if any change in resistance to rolling of the edge. In some SET test data harder steel rolled more than softer steel.
EOU also performed tests comparing edges hardened and then sharpened, to edges that were sharpened and then hardened. The latter performed no better than the former, corroborating SET tests that hardness is not substantially influential as far as resistance to rolling is concerned.
But maybe the most encompassing and overriding consideration of all is that our very sharp edges are extremely thin. We are talking fractions of a micron thin. That’s really super thin. There is just not much steel there. I liken it to supporting a car with an egg. Obviously if you attempted to support a car off the ground with an egg it would simply crush the egg and make an ugly mess of the egg. What about two eggs? After all that would be twice as strong! What about 10 eggs? Ten times the strength!
Again, our very sharp edges are very thin. I placed a potato on a scale and sliced through it with a very sharp, 150 or so edge. It required 5+ pounds of pressure to slice the potato. I postulate that due to the extreme thinness of sharp edges, the difference in hardness between HRC 52 and HRC 60 is more or less irrelevant. There just is not enough steel there to significantly impact the outcome. So, one egg or ten eggs, is still going to result in a disgusting gooey mess. Relating this to the subject at hand, even if there is some change in hardness due to sharpening, it is again irrelevant.
Disclaimer:
I am perfectly open and willing to entertain and accept evidence showing that judicious belt sharpening substantially impacts edge performance. And, I would do so with alacrity. That said, I sharpen with a Kally. It is very fast and produces extremely sharp and perfectly serviceable edges. I have seen no real-world difference in edge performance between Kally sharpened edges and those that I have sharpened on my water cooled Tormek T7.
And, you are going to have to pry my Kally from my cold dead fingers before I’m going to sharpen all my knives by hand.
Comments? Ideas? All welcome!
I’m in no way intending any declaration of fact, but rather, expressing what I think is going on and why. I’m hoping others with chime in with evidence or suggestions pro or con. It’s an exploration of issues rather than a collection of conclusions.
I’m going the preface this with the phrase “for all intents and practical purposes”. Admittedly, there are specific applications where, for example, a possible 10% difference may be significant. I only add this because this about general knife sharpening and I wish to avoid becoming mired in minutia.
I may be right or I may be wrong. But, I hope to say it in such a convincing way that even if you think I’m wrong, you will have to at least think I might be right. (That might be paraphrased from something Bob Dylan said.)
That said, IMHO, evidence so far presented indicates that:
Judicious sharpening with a Kally does not heat the blade anyway near enough to impact performance.
Q: How do you know there is not flash molecular level heating at the very apex of the edge?
A: I don’t and probably never will. And, for all intents and practical purposes, I think it to be irrelevant. Even if there is heating, it is an extremely ephemeral event both in heating and cooling. Neither heating nor cooling is sustained long enough to anneal or temper hardened steel.
Q: Assume there is super heating of the surface at the apex, could the super heating and rapid cooling actually harden the surface leaving soft metal just beneath?
A: Like a chocolate chip cookie? Do you mean like crispy on the outside and chewy on the inside? Who knows? Who cares? I guess maybe it’s possible at the molecular level, but again irrelevant. If indeed something like occurs, any ramification at the apex is so insignificant that it would be undetectable whilst chopping carrots or SET testing. While intellectually entertaining, I think this line of thinking is getting lost in minutia and missing the forest for the trees.
Q: Have you seen evidence supporting that belt grinding significantly impacts edge hardness or performance?
A: Yes. But it is very scant. Mr. KG presented evidence supporting the possibility that powered sharpening may impact edge performance in some circumstances. However, and I will discuss this shortly, that for all intents and practical purposes, the bulk of evidence I’ve seen so far is indicative to the contrary.
Q: Does harder steel, say, RHC 60, perform better and last longer than RHC 52?
A: Maybe. A little. Both EOU SET testing and Mr. KG presented data that indicates that in some cases there may be slightly better edge retention. However, this data is neither generalized nor conclusive and definitely not the case in most circumstances. Furthermore, there are disadvantages to harder steel such as difficulty sharpening and chipping that may overweigh any possible advantage. Moreover, in some of the EOU SET tests, softer steel rolled less than harder steel.
Mr. Reich astutely noted that all knives are ground sharp in the first place. I saw a video of the knives being sharpened at, if memory serves correctly, (correct me if I’m mistaken) the Hinckel factory. They were sharpening on large, dry grinding wheels. It’s not as if mother knife gave birth to baby knives and they are born, they are ground sharp.
Notes:
EOU SET testing data indicates that that in general there is no significant difference in resistance to rolling between HRC 52 and harder steel. Even if edge softening occurs as the result of sharpening, it is mitigated by the data indicating that as far as range of hardness used in knife steel there is little if any change in resistance to rolling of the edge. In some SET test data harder steel rolled more than softer steel.
EOU also performed tests comparing edges hardened and then sharpened, to edges that were sharpened and then hardened. The latter performed no better than the former, corroborating SET tests that hardness is not substantially influential as far as resistance to rolling is concerned.
But maybe the most encompassing and overriding consideration of all is that our very sharp edges are extremely thin. We are talking fractions of a micron thin. That’s really super thin. There is just not much steel there. I liken it to supporting a car with an egg. Obviously if you attempted to support a car off the ground with an egg it would simply crush the egg and make an ugly mess of the egg. What about two eggs? After all that would be twice as strong! What about 10 eggs? Ten times the strength!
Again, our very sharp edges are very thin. I placed a potato on a scale and sliced through it with a very sharp, 150 or so edge. It required 5+ pounds of pressure to slice the potato. I postulate that due to the extreme thinness of sharp edges, the difference in hardness between HRC 52 and HRC 60 is more or less irrelevant. There just is not enough steel there to significantly impact the outcome. So, one egg or ten eggs, is still going to result in a disgusting gooey mess. Relating this to the subject at hand, even if there is some change in hardness due to sharpening, it is again irrelevant.
Disclaimer:
I am perfectly open and willing to entertain and accept evidence showing that judicious belt sharpening substantially impacts edge performance. And, I would do so with alacrity. That said, I sharpen with a Kally. It is very fast and produces extremely sharp and perfectly serviceable edges. I have seen no real-world difference in edge performance between Kally sharpened edges and those that I have sharpened on my water cooled Tormek T7.
And, you are going to have to pry my Kally from my cold dead fingers before I’m going to sharpen all my knives by hand.
Comments? Ideas? All welcome!