10-30-2018, 03:43 PM
I'm intrigued that we have so many threads on this topic. Honestly, I've been avoiding comment. I have been waiting to find out what the general consensus might be without my input.
With such concise, pertinent questions, I will attempt similar answers of my understanding.
1) Q: How do you know there is not flash molecular level heating at the very apex of the edge?
Where have you seen hard evidence? Can you back this up scientifically? I don't mean seeing a few off the wall studies. Is there any commonly accepted evidence in the scientific community about the possibility or description of flash heating due to some sort of "dark energy" produced by the act of separating molecules?
Here's what it looks like from a knife maker's point of view... Sharpeners remove an insignificant amount of material from a blade compared to the amount and percentage of material removed while a knife maker grinds the entire side of a blade. Compare the primary bevel to the secondary bevel. Let's say the edge bevel is 1/16" wide, and the blade is 1" tall. I'd be producing 16x as much mystery heat grinding the secondary bevel to an edge thickness of .010- .015". Where's the heat? Am I tempering the surface steel of the entire blade?
2) 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?
Absolutely not. Phase transformations require an excess amount of heat. That means the steel must go through an austenite phase exceeding 1400 degrees at the very least, and it must remain at that temperature until it is rapidly cooled upon quenching. I've done many thousands of phase transformations. Every knife I make is edge hardened with an O/A torch. I have to be able to distinguish the flash of color that tells me the edge is austenitic. If you look at the vivid quench line revealed through etching, I'm pretty darn consistently getting half the blade austenitic, which results in the martensitic transformation of that amount of steel upon quenching. It requires an absurd amount of heat. "Red hot" isn't even close to phase transformation.
3) Q: Have you seen evidence supporting that belt grinding significantly impacts edge hardness or performance?
Nope. Not ever. Think about how many knives are produced per day by major manufacturers. Do you think ANY of them would risk the initial cutting performance of their blades at the very last step of production? Have you ever heard of a manufacturer boasting about how they finally figured out how to finish an edge without overheating it like all the other sharpeners in the world?
4) Q: Does harder steel, say, RHC 60, perform better and last longer than RHC 52?
I believe I've read that Mr. KG has observed a distinction between RHC 56 and RHC 58 in real life use by guys who do nothing but cut meat all day every day. I believe thousands of CATRA tests have shown harder steel is more Wear Resistant than softer steel. Every knife maker and every knife manufacturer focuses on heat treating their blades optimally. It's the single most important aspect of making a cutting blade, and everyone runs their blades as hard as they can be without getting too chippy. That means zeroing in on a final RHC of no more than one point RHC. Why is everyone so specific if it doesn't matter? Why would they be specific and then alter the hardness by sharpening the edge?
In light of precise modern manufacturing tolerances, thousands of brand new blades are sharpened every day, if not every hour, by powered grinding of one type or another. Thousands of knives are re-sharpened every minute, probably only including professional sharpening for professional cutters. What percentage of these professionals are complaining about soft edges?
This isn't new ground. Nobody has made a stunning breakthrough in the past hundred years. Weigh this out for yourself. There's a group of people who are absolutely fine with powered sharpening, and a group of people who claim softened edges due to some mysterious type of heat generation that no one can scientifically sustain.
Thank you for laying out your poignant questions, Mr. Grepper.
With such concise, pertinent questions, I will attempt similar answers of my understanding.
1) Q: How do you know there is not flash molecular level heating at the very apex of the edge?
Where have you seen hard evidence? Can you back this up scientifically? I don't mean seeing a few off the wall studies. Is there any commonly accepted evidence in the scientific community about the possibility or description of flash heating due to some sort of "dark energy" produced by the act of separating molecules?
Here's what it looks like from a knife maker's point of view... Sharpeners remove an insignificant amount of material from a blade compared to the amount and percentage of material removed while a knife maker grinds the entire side of a blade. Compare the primary bevel to the secondary bevel. Let's say the edge bevel is 1/16" wide, and the blade is 1" tall. I'd be producing 16x as much mystery heat grinding the secondary bevel to an edge thickness of .010- .015". Where's the heat? Am I tempering the surface steel of the entire blade?
2) 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?
Absolutely not. Phase transformations require an excess amount of heat. That means the steel must go through an austenite phase exceeding 1400 degrees at the very least, and it must remain at that temperature until it is rapidly cooled upon quenching. I've done many thousands of phase transformations. Every knife I make is edge hardened with an O/A torch. I have to be able to distinguish the flash of color that tells me the edge is austenitic. If you look at the vivid quench line revealed through etching, I'm pretty darn consistently getting half the blade austenitic, which results in the martensitic transformation of that amount of steel upon quenching. It requires an absurd amount of heat. "Red hot" isn't even close to phase transformation.
3) Q: Have you seen evidence supporting that belt grinding significantly impacts edge hardness or performance?
Nope. Not ever. Think about how many knives are produced per day by major manufacturers. Do you think ANY of them would risk the initial cutting performance of their blades at the very last step of production? Have you ever heard of a manufacturer boasting about how they finally figured out how to finish an edge without overheating it like all the other sharpeners in the world?
4) Q: Does harder steel, say, RHC 60, perform better and last longer than RHC 52?
I believe I've read that Mr. KG has observed a distinction between RHC 56 and RHC 58 in real life use by guys who do nothing but cut meat all day every day. I believe thousands of CATRA tests have shown harder steel is more Wear Resistant than softer steel. Every knife maker and every knife manufacturer focuses on heat treating their blades optimally. It's the single most important aspect of making a cutting blade, and everyone runs their blades as hard as they can be without getting too chippy. That means zeroing in on a final RHC of no more than one point RHC. Why is everyone so specific if it doesn't matter? Why would they be specific and then alter the hardness by sharpening the edge?
In light of precise modern manufacturing tolerances, thousands of brand new blades are sharpened every day, if not every hour, by powered grinding of one type or another. Thousands of knives are re-sharpened every minute, probably only including professional sharpening for professional cutters. What percentage of these professionals are complaining about soft edges?
This isn't new ground. Nobody has made a stunning breakthrough in the past hundred years. Weigh this out for yourself. There's a group of people who are absolutely fine with powered sharpening, and a group of people who claim softened edges due to some mysterious type of heat generation that no one can scientifically sustain.
Thank you for laying out your poignant questions, Mr. Grepper.