Managing expectations of edge retention

[JoeBusic]

I would use
Edge Retention(wear) and
Edge Stability(deformation resistance)

Edge holding and retention are the same, in my opinion.

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.)

Thanks guys. Edge STABILITY is already set. Larrin explained the term in his article "Edge stability" using Roman Landes as source. German is stabilitat. Roman already set the importance of edge stability and in combination with edge retention can render different conclusions than edge retention alone.

 

[Justin W]

soooo....

back to the topic at hand; as D DevinT mentioned in a slightly unrelated thread "Design is everything"

when you design a knife, and you plan for how it's going to be used, you choose a thickness of steel that provides the optimal attributes for the intended design. You choose a width, based not only on the thickness you choose, but for the intended use as informed by your design. Then you choose the primary bevel angle(s) and choose where it/they will terminate toward the spine and toward the edge. Then you choose how far up that primary bevel your secondary bevel is going to go/your secondary bevel angle...

all these choices...

they determine so much more about how a given knife is going to perform at its given job than so many other factors that some of us are overly obsessed with, in this thread, at the moment. It would be cool to focus on these other things instead of the effects of sharpening heat has on an edge- which in my view is an entirely different conversation.

the choices made that go into the design of a knife are the most interesting topic, because it gives insight into how and why knifemakers do what they do, and why they are successful at making a good knife or not. Getting bogged down in all this mumbo jumbo is ruining a potentially very enlightening conversation. In my opinion.

I agree. When someone gets one of my knives from me directly, I give them the straight answer. "This isn't magical super steel. The best way to keep it sharp is to not let it get too dull. Strop it every few days/weeks, and sharpen it when the strop seems to not work any more. I use flat water stones, not gimmicky doohickies to sharpen, and you should too."

If they don't care, they don't care. If they do care, they probably have some means to keep it sharp. When they get it from me, it is as sharp as I can make it, and I think that can be a bit of a wakeup call for what "sharp" really means.

 

[Skiller1nc]

I'm shocked by the amount of big names in this thread who seem fully incapable of having an adult discussion, people's whose options and experience I respect. Geez guys grow up. Almost everyone here is making good points and counter points, yet you all feel the need to cuss, threaten to leave for your metal health, and spout nonsense. Some people still come here to learn, let's make it a conducive environment for that.

 

[REK Knives]

What you said. I was trying to not get too nerdy … but what ran through my head was “what grit?”, “what contact area?”, “what pressure?”, “what speed?”, “do any of those relate to the conditions of sharpening?” and especially (as landes himself noted) there is a huge heat sink of metal around the contact point which will very very quickly dissipate the energy … so how the heck could a (relatively huge) thermocouple, removed from the point of contact register such a high temperature (unless maybe the thermocouple WAS the point of contact … which would invalidate the result)

I asked those questions years ago on hypefreeblades forum directly to Roman and never got a direct answer. Those are all variables that make a huge difference. But that being said I grind under coolant with a set up inspired by Nathan the Machinist from a video he did years ago

 

[Blues]

So, it's good to see that you guys took my advice to heart.

Have fun and don't cut yourselves.

I'm gonna go have a beer.

 

[Rick Marchand]

I'm shocked by the amount of big names in this thread who seem fully incapable of having an adult discussion, people's whose options and experience I respect. Geez guys grow up. Almost everyone here is making good points and counter points, yet you all feel the need to cuss, threaten to leave for your metal health, and spout nonsense. Some people still come here to learn, let's make it a conducive environment for that.

I’m glad you are sensible and if you are here to learn….. but with all due respect, you have no idea how much the dynamic of this forum has changed. Those who know me and know my posting history have been flooding my various inboxes( on and off-site) with comments like “It’s about time” and “thank you for stepping up”… along with a few “is everything okay?” Lol… it is out of character for me, indeed… but sincerely, I am harbouring a tremendous amount of guilt for not taking a hard stand back when it meant something. Instead, i tried to keep the peace, when the majority of my friends and mentors were either pushed away or chose to abandon this sub forum for the exact reasons I lost my cool, today. No apologies. I mourn the days when fact, experience and expertise, held more weight than feelings, opinions and 5 second Google searches. I take pride in communicating on these forums as if I’m speaking face to face with the members… that has not changed.

 

[Rick Marchand]

I will apologize to D DevinT for derailing his thread. He deserves that.

 

[Lorien]

^I just wish I had been making knives and more active in this subforum back then- talk about big names! I think it might be possible to turn things around in here, and that's one of the reasons I'm here- I'm an optimist! (not because I think I can change anything, lol)

also, wrt 'big names'...don't forget, behind every big name is just a dude. In this case, a very sincere, honourable, dedicated, good dude.

 

[DevinT]

I had a guy on this forum tell me that I should do more reading and less posting, at the time I had a few hundred posts and he had over 20,000 posts. Luckily, there were lots of makers here that knew me and my body of work that told him how dumb he sounded.

Some newer knife makers don’t know the struggle that it has taken to get to this point.

I highly recommend that makers study Landes, Verhoeven, Pendray, Howard Clark, the founding members of the guild and the ABS etc. to see how we got here.

Rick Marchand much love and respect.

Hoss

 

[DeadboxHero]

REK Knives C Cushing H. EngrSorenson
"Messerklingen Und Stahl" pg 134, Roman Landes, 2006

"Grinding surface briefly brought up to 2000°C within 1-3um of depth"

That's not the important part though, I think folks are focusing on the wrong piece of information here.

What Landes is trying to convey is the heat moving to the thinner cross section towards the edge which is the big problem causing micro tempering (reduced hardness/strength) aka less cutting edge retention, less deformation resistance.

 

[dwaterfield]

As a newbie around here, I'm just hoping that Mom and Dad will stop fighting soon.

I do appreciate the technical parts of the thread though, and it's convinced me about the next tool for my shop. I've seen other threads that advised the use of Kool Mist or similar systems. Time to start shopping for one.

 

[DeadboxHero]

Nathan the Machinist
Close up on the used and abused edge CPM Rex 45. Matrix corrosion exposing carbides (M6C/MC 8% vol. 2-3um diameter) some edge rolling seen bottom right possibly due to not removing a wire edge during previous sharpening. Depth of field blur due to difference in height from matrix corrosion area and surrounding area without exposed carbides.
Things get pretty cool if we look closely enough, these things are not unique to CPM Rex 45.

 

[Robert Ptacek]

There seems to be misunderstanding in the posts here about why it says "no water" well in this case its because the cBN is mounted on a surface that can rust, the thinking was to embed the cBN into a different surface than what's typically used to improve tear out resistance, so in the specific case, they want you to use "no water" to prevent corrosion. I talked to Sal about his cBN stone in 2019 at the Eugene Oregon Knife show, he also bought one of my Vitrified cBN stone prototypes which was nice of him.

As you can see, I am using water, no one died, just be sure to dry the surface when done.

Deadboxhero is a sharpening maestro.

 

[Natlek]

REK Knives C Cushing H. EngrSorenson
"Messerklingen Und Stahl" pg 134, Roman Landes, 2006

"Grinding surface briefly brought up to 2000°C within 1-3um of depth"

That's not the important part though, I think folks are focusing on the wrong piece of information here.

What Landes is trying to convey is the heat moving to the thinner cross section towards the edge which is the big problem causing micro tempering (reduced hardness/strength) aka less cutting edge retention, less deformation resistance.

We invent hot water again ? Sharpen that MF knife on belt grinder on 15 degree ! Than hand sharpen it on 18 degree / my favorite angle/ and you are DONE !!!! No burn ziilion of microns of edge anymore !! At least that is what I am doing !

BTW , I can find tons of videos where *big names* sharpen knife on grinder !
You don t need to be a *big name* or a rocket scientist to come to a conclusion on your own! You just need the will to try and experimenting !

My post from 2018 from this thread https://www.bladeforums.com/threads/cbn-wheels-for-sharpening.1623595/

@razor-edge-knives , sharpened edge on my HSS blades last much longer when I sharpen them with diamonds compared to stone and ceramic belts sharpening ? CBN will CUT any kind of carbides will not tear them from matrix.... ?

 

[Stacy E. Apelt - Bladesmith]

OK folks, I take a few days away from reading every post on what seemed a somewhat boring technical thread ... and come back to find that the thread is turning into FUBAR.
Blues tried to tone it down, but it didn't help.


Rick - I understand why you are worked up but tone the language down and try to keep it civil.

Cushing - Please don't get so technical that people stop reading what you write. Sometimes it is OK not to dispute everyone's statements.

Joe, Natlek, and the others - just let it go. There is nothing more to be said here.

 

[Stacy E. Apelt - Bladesmith]

Now, to turn this thread in a more humorous and friendly way:
I had a fellow at a knife show ask me how I sharpened my knives. I told him I have several ways, depending on the use and the desired degree of sharpness. I said I used a belt grinder with a coolant spray for large knives and swords, diamond plates for field knives, and Japanese water stones for some high-end chef's knives. I explained that some knives needed a more ragged edge and others a very smooth and thin edge. Most were done in less than a minute on a 220-grit belt and given a quick buff to remove the wire, while others took as much as half an hour to get screaming sharp going up to 14,000 grit.
He said that was all modern mumbo-jumbo nonsense ... he learned to sharpen knives from his grandpa, using a wet stone (sic) and motor oil. His granpa had used the same stone his whole life and could take the edge to one atom thin. I said a whetstone was a perfectly good way to sharpen a knife, and politely commented that a one atom edge was not possible for several metallurgical and physical reasons. He said, "Well, the proof is in the puddin', my grandpa butchered hogs for a living and would only sharpen his butcherin' knife once a year."
I smiled, told him I hoped he had a good time at the show, and turned to the next person at the table. No need to spend any more time trying to change his mind or disparage his grandpa's stories.

 

[Lorien]

I don't think I'd be buying my pork chops from a butcher who uses motor oil to sharpen his knives...

 

[running bird]

I don't think I'd be buying my pork chops from a butcher who uses motor oil to sharpen his knives...

Maybe the motor oil pork chops are what enabled him to sharpen down to the atomic level! i think he might have been onto something…

 

[Cushing H.]

OK folks, I take a few days away from reading every post on what seemed a somewhat boring technical thread ... and come back to find that the thread is turning into FUBAR.
Blues tried to tone it down, but it didn't help.


Rick - I understand why you are worked up but tone the language down and try to keep it civil.

Cushing - Please don't get so technical that people stop reading what you write. Sometimes it is OK not to dispute everyone's statements.

Joe, Natlek, and the others - just let it go. There is nothing more to be said here.

Ok Stacy ... but I think there are some things here that are interesting to discuss. Lets take as a given that with belt sharpening (no matter what precautions taken, like flooding, very slow speed, light pressure, etc) there is some heating of the very tip of the edge that results in loss of hardness, *but* that would be worse at the very very thin edge, and not so bad (if present at all) in the *relatively* thicker material behind the very edge. )

So, if this is the case, with some usage, that really soft material at the extreme edge will wear away, right??? Leaving, behind it, a still really thin, but hard, backing of steel that will stand up to use without wearing down. Is this a reasonable expectation????

I keep coming back to Horsewrights experience that found no difference between belt sharpened and stone sharpened blades.....

 

[EngrSorenson]

REK Knives C Cushing H. EngrSorenson
"Messerklingen Und Stahl" pg 134, Roman Landes, 2006

"Grinding surface briefly brought up to 2000°C within 1-3um of depth"

That's not the important part though, I think folks are focusing on the wrong piece of information here.

What Landes is trying to convey is the heat moving to the thinner cross section towards the edge which is the big problem causing micro tempering (reduced hardness/strength) aka less cutting edge retention, less deformation resistance.

Understood, and I appreciate what you've done here- thank you. I'm not surprised in the least that power-anything on a knife edge could impact it it's temper, and this wasn't really the information I was interested in, but I'm pleased that you care enough to do this.

I don't think anybody is arguing that you need water to prevent your edge from overheating with a hand sharpening stone.

Just so you understand where I'm coming from, post number 4 of this thread included the following:

Even hand sharpening on a dry diamond plate can overly temper the apex.

perhaps I might have missed it where we've all decided this isn't true- but as I've followed a long, it seems that there's supposedly test data and an expert that confirm this statement. Supposedly it's in that book! Well anyway, this isn't the place to continue this discussion, but I wanted to clarify for anyone who might be misinterpreting some of my posts.

On topic, however, I think manufacturing methods are a concern common folks like myself don't often consider. Most of the knives I own have reasonable QC in the aspects pertaining to metallurgy, and then some guy "hand sharpens" the knife against a grinding wheel for it's secondary bevel. I've had the thought before that my knives get better as I sharpen them, but I've often thought it was me building familiarity with a specific knife as I sharpen it. It's interesting to see that once again expectations for sharpness can be thwarted by a seemingly minor processing. When I finally get around to buying nicer (ie, more expensive) knives, a selling point for me will be how much care is put into cutting the final bevel.