Managing expectations of edge retention

EngrSorenson said:
I think it’s true that I’m spoiled because I keep my knives screamin’ sharp- I feel like anything less just isn’t sharp. “Sharp enough” is definitely something I’ve lost an appreciation for. It’s good to remember what that’s like.
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Lol. Maybe, maybe not. My in-laws have several kitchen knives that they store by tossing them in a drawer. Every time i go there they (every one) are dull, dull, dull (like trying to cut a carrot you need to use a lot of force, and they produce a rough split in the carrot …. Not a slice. And yet, they have in that same drawer a simple hand held “V” notched ceramic sharpener that i will use to make one or to of the knives bearable to use. They will comment “oh, this is so nice and sharp” … but when i leave all knives go back to dull, dull, dull.

They notice the difference, but appear to just not care enough to touch up even one blade…
 
EngrSorenson said:
I would also be surprised by this. The apex is small, but steel is a good conductor of heat and there’s such a small amount of heat generated that I cannot imagine the apex changing it’s temper against the relatively cool surface of a stone. Maybe if I tried my fastest, pressing hard? Idk.
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Roman Landes, did an experiment years ago... using thermocouples and saw temps approaching 1000F or something crazy high like that. He linked his work on the hypefreblades site. Those few microns at the apex are very susceptible to overheating and are the first line in edge retention. I'll try to find the study.... maybe Kev C. remembers.
 
I would use:

Abrasive wear resistance (for abrasive wear resistance)
Edge stability, (both fine and gross) for resistance to non abrasive edge loss from rolling, chipping, mushy edge etc
Edge retention (for the ability to retain an edge). This is generally a combination of both edge stability and wear resistance and the material being cut and how it is being cut. This is a complex intersection of a number of variables which is why it is so tempting to describe edge retention as wear resistance but it really is not. To the average user, and for everyone maker discussing edge retention, they usually literally mean the ability to retain an edge (in their normal use.)

A great example of this is: AEBL has better edge retention (in thin narrow geometry) than S30V in my kitchen chopping celery against a cutting board or when mom cuts against a plate because it has better edge stability than S30V and the abrasive wear resistance of S30V doesn't pay a dividend in this application (my food isn't abrasive).
 
Rick Marchand said:
Roman Landes, did an experiment years ago... using thermocouples and saw temps approaching 1000F or something crazy high like that. He linked his work on the hypefreblades site. Those few microns at the apex are very susceptible to overheating and are the first line in edge retention. I'll try to find the study.... maybe Kev C. remembers.
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Sorry … but not sure how much i would trust this study. Thermocouples are *huge* compared to the apex, and at the very least would distort the readings by their presence.
 
This is why Shop Talk is an empty husk of what it once was. I thank those of you trying to keep it civil and on topic. Every thread seems to deteriorate into passive aggressive awkwardness. Every single attempt to rejoin the discussion, only serves to remind me why I take long breaks from it. The toxicity is stifling. Sorry for the glum reply. I'll take my leave again.
 
He is a PhD metallurgist and, if I'm not mistaken, this was actually a part of his PhD thesis. I think he gave a dissertation on this and had to defend a thesis. I don't have all the facts either, but I'd be willing to bet that somebody along the way thought of that.

However it is also common sense to me that sharpening a normal edge on a normal knife on a normal stone, with normal pressure while it is dry, is not going to wreck anything. Maybe if you have a very narrow angle and you're using the knife for eye surgery or something like shaving whiskers like a straight razor (or, you know, commercial razor blades like Roman was doing,) it might be more relevant.
 
Cushing H. said:
Sorry … but not sure how much i would trust this study. Thermocouples are *huge* compared to the apex, and at the very least would distort the readings by their presence.
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You don't trust Roman Landes' study? I'm not sure what to say.... maybe you can doubt my recollection... perhaps "thermocouple" is the wrong word, which would be my mistake. The experiment is real and accurate. Dr. Landes is a trustworthy expert in metallurgy
 
Rick Marchand said:
You don't trust Roman Landes' study? I'm not sure what to say.... maybe you can doubt my recollection... perhaps "thermocouple" is the wrong word, which would be my mistake. The experiment is real and accurate. Dr. Landes is a trustworthy expert in metallurgy
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Logical fallacy number 9! Appeal to authority!



(Do y'all see how obnoxious that is?)
 
Rick Marchand said:
Roman Landes, did an experiment years ago... using thermocouples and saw temps approaching 1000F or something crazy high like that. He linked his work on the hypefreblades site. Those few microns at the apex are very susceptible to overheating and are the first line in edge retention. I'll try to find the study.... maybe Kev C. remembers.
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Here is a respective quote from Landes, if that helps:

“Grinding generates energy (heat) and every step of sharpening is
grinding even the strop. This heat can be sucked away by the right
coolant such as water. If the grinding action lacks the coolant,
the heat goes mostly into the torn out part and the body (blade/edge)
it was torn off. It becomes obvious to see the induced energy when you
see the sparks fly (Burning steel!!).

Depending on how hard you go over the piece the more energy is induced
the hotter it gets, thats basic physics. Than the guys come and say
but I can do it so sensitive that the edge will not suffer and I’m
dipping the blade each run into cold water…. Well that is a nice
effort, but when it comes down to the very edge this tiny fraction
is overheated faster, than the eye can see or the wrinkled fingers
can feel. Unfortunately the edge becomes thinner the close you come
to the very edge/point means generated heat will get jammed in the tip.
In addition to that tempering colors that would visually proof this are
ground away immediately when they appear. and Stainless steels need
a higher temperature to generate tempering colors and longer time to
build them up. Nevertheless one can do metallurgical examination that
can proof the issue testing micro hardness There are some old german
study’s that examined this issue in the very detail.

I had a book dedicated to general grinding methods, in this book i found
a test application. A normal steel block apx. 2″x2″x4″ that had a
large number of highly sensitive thermocouples integrated in the surface.
The block was slit dry by hand over a 1000grit grinding paper. The peak
temps measured, walked up to 2000°C for split seconds in the very
surface (some microns). Of course the block did not melt since the
volume fraction of induced heat was to tiny to affect such a large solid
piece of steel. But the effect was there and proofen. In a edge we just
talk about some microns of material, here the effect is solid an clear.
Every manufacturer of razorblades knows this and does excessive cooling
whilst grinding and polishing edges, that need to hold an super sharp
edge for very long. It seems just some the magic makers out of the
custom knife scene think, the physical principles like this, do not
apply to them….”

Note the mention of razor blades, Nathan the Machinist Nathan the Machinist (as you suggested).

PS: not a maker, obviously, just an interested bystander and possible customer of you guys :)
 
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Rick Marchand said:
This is why Shop Talk is an empty husk of what it once was. I thank those of you trying to keep it civil and on topic. Every thread seems to deteriorate into passive aggressive awkwardness. Every single attempt to rejoin the discussion, only serves to remind me why I take long breaks from it. The toxicity is stifling. Sorry for the glum reply. I'll take my leave again.
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You should come over to my sub! We have about as much traffic as shop talk and everything there is my favorite subject! Me!! ...and Matt Gregory's mom...
 
Rick Marchand said:
You don't trust Roman Landes' study? I'm not sure what to say.... maybe you can doubt my recollection... perhaps "thermocouple" is the wrong word, which would be my mistake. The experiment is real and accurate. Dr. Landes is a trustworthy expert in metallurgy
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“Dont trust” is probably too strong a statement. More accurate is “i would have many questions about the experimental setup”. Even in (edit) feriders quote from him, i see both some anecdotal statement as well as some apparently internally contradictory statements that raise questions for me.

This is not even to mention that when you start talking about microns of thickness, even defining what the temperature of a material is becomes really difficult and open to interpretation (atomic electron shell excitation? Just which atom - which element? Matrix vibrations? If you are really that thin, there just might not be enough matrix present to even create those vibrations. Phase rearrangement requires diffusion, which requires both enough time (which might not be available with such a transient effect), and material nearby to diffuse (which might not be present if you are talking angstroms of thickness).

Ive seen many experiments that were badly designed, even when it comes to fundamentals … and produced either flawed or misleading results … including a surprising amount from nationally recognized researchers. So … trust, based only on a statement and someones name? Heck no. Trust after knowing the details … maybe.
 
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Richard338 said:
We don't talk about temperature in the limit of just a few atoms or molecules, but a micron is nearly 20,000 atomic units, so the temperature of a blade should be well-defined, even locally such as near the apex.
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Understood. I was really just trying to make the point that things get really, really hard to measure (and define) as you get to really small geometries (and my use of “micron” was not meant as absolute statement of the dimension of the extreme end of an edge … but was just meant to convey that its features can be really, really small, especially if you consider scratch marks)
 
At some point you have to believe that the goddamn experts know how to do their job. This is insane. People like, Roman and Larrin, most likely know how to conduct an experiment, with regard to their own fucking profession. So lose the contrarian filter and save the word salad for your discussion with, Roman.

I'm unfollowing this thread, for my own mental health. Enjoy.
 
Cushing H. said:
“Dont trust” is probably too strong a statement. More accurate is “i would have many questions about the experimental setup”.
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I concur. There are so many variables at play that, although perhaps peak temperatures is localized spots reached 3632 F I would find it hard to believe that there's any practical change in the metal. Even if there was, the test itself would be so hard to conduct in such a way to account for everything.
I had a book dedicated to general grinding methods, in this book i found
a test application. A normal steel block apx. 2″x2″x4″ that had a
large number of highly sensitive thermocouples integrated in the surface.
The block was slit dry by hand over a 1000grit grinding paper. The peak
temps measured, walked up to 2000°C for split seconds in the very
surface (some microns).
Click to expand...

For instance, the surface area of the block touching the sand paper was likely 8 square inches. Significantly larger than the size of the average bevel.
I would have also been interested to see if there was a pattern in the temperatures- I would guess that the back of the block would have the highest temperatures, as it's crossing over sand paper that has already generated heat from friction.
I would be interested to know if the sand paper was insulated.
I would want to know how fast the block traversed the sand paper (and in what orientation).
a 2x2x4 block of steel is what... about 5 lbs? that would be a little more than half a pound per square inch. I wonder how good of an approximation that is for sharpening?
Like you said before, I'd also like to know how the experiment accounts for the Heisenberg uncertainty principle in the thermocouple measurements.

My day job is testing complex systems, so I know how experiments can be rife with problems.
The smaller a thing is, the harder it is to test- note that even here, the test uses a steel block as a surrogate for a knife bevel and I'm not sure that is a good approximation due to the changes in convective heat transfer and the total heat generated.
 
Rick Marchand said:
scroll up... you are free to believe what you want. Perhaps you should contact, Dr. Landes. Maybe ferider ferider made it up. IIRC, there were more details to this study in the post Roman made on hypefreeblades ... or you could just find the actual paper and translate it.
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Again, i did not say i did not believe it …. I said basically i would not take it as gospel until or unless i saw clear statements of experimental setup and the resultant data. If i “scroll up”, what i see is (well intentioned) anecdotal statements that in themselves raise questions.
 
Rick Marchand said:
At some point you have to believe that the goddamn experts know how to do their job. This is insane. People like, Roman and Larrin, most likely know how to conduct an experiment, with regard to their own fucking profession. So lose the contrarian filter and save the word salad for your discussion with, Roman.

I'm unfollowing this thread, for my own mental health. Enjoy.
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Oh my … so much for clear and forthright discussion on data and related information.
 
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