Managing expectations of edge retention

DeadboxHero said:
Its been almost a whole year since it was sharpened and it was nicely maintaining a sub 500g BESS edge with heavy use.
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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.
 
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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the instructions for the spydie cbn tell you to use up to medium pressure, but don't say why
 
Nathan the Machinist said:
... for the record I have burned the sh*t out of some knives accidentally taking a heavy cut with a CBN plated aluminum grinding wheel. Even using flood coolant I ran colors.
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Sharpening on a CBN is low speed, no pressure. How fast did you go?
 
Lorien said:
the instructions for the spydie cbn tell you to use up to medium pressure, but don't say why
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Because its a single layer of cBN imbedded in a surface, its to reduce premature sheering and dulling of the abrasive grains.

Here is a magnified view of the cBN abrasive on a fresh new Spyderco double sided cBN bench stone.

https://imgur.com/ZmiB4SB

Here is a magnified view of a well worn, used and abused DMT electroplated diamond "stone" the corners are bald because they see more force which sheers and wear away that single layer.

https://imgur.com/wucki2G

Regardless, the abrasive grains will wear away with lots of use but due to the single layer construction with no binder or more cBN/diamond layers you'll see faster wear with heavy pressure due to abrasive tear out rather than letting those expensive abrasive grains wear out (fracture/blunt) from cutting.
 
JoeBusic said:
Sharpening on a CBN is low speed, no pressure. How fast did you go?
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2450 SFM. That's very very slow for grinding with CBN, or anything really. Feed rate is 20 inch per minute. A heavy cut under those parameters will burn your work. Even under ~10 GPM flood coolant. Thinking the aluminum wheel will prevent an issue with heat while grinding is wishful thinking.
 
To be clear I'm talking about powered grinding with a CBN wheel. Not hand sharpening on a CBN (or diamond) stone.

My point being, any powered grinding can create an issue with heat. It doesn't matter if the wheel is aluminum. I'm speaking from (substantial) experience.
 
DeadboxHero said:
Because its a single layer of cBN imbedded in a surface, its to reduce premature sheering and dulling of the abrasive grains.

Here is a magnified view of the cBN abrasive on a fresh new Spyderco double sided cBN bench stone.

https://imgur.com/ZmiB4SB

Here is a magnified view of a well worn, used and abused DMT electroplated diamond "stone" the corners are bald because they see more force which sheers and wear away that single layer.

https://imgur.com/wucki2G

Regardless, the abrasive grains will wear away with lots of use but due to the single layer construction with no binder or more cBN/diamond layers you'll see faster wear with heavy pressure due to abrasive tear out rather than letting those expensive abrasive grains wear out (fracture/blunt) from cutting.
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that is cool!
 
Lorien said:
the instructions for the spydie cbn tell you to use up to medium pressure, but don't say why
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I mean… medium pressure is such a subjective thing… but if overheating was the concern, they could provide other instructions, such as slow speed on each pass. There might be other concerns- potential damage to the product, potential damage to the knife…

I mean we live in a society where hot coffee cups say “caution, contents may be extremely hot”. Might just be to say “we told you not to”.

ETA: looks like DBH solved it lol. Damage to the product it is.
 
Larrin said:
I have never seen the term "edge holding" used to refer to plastic deformation before. Edge retention has been used interchangeably with edge wear, I am as guilty of that as anyone, though perhaps the more universal definition is simply the ability to maintain sharpness, regardless of the mechanism involved for dulling.
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What would the term be for the definition? Edge stability? Something else? Something has to be. There is a possibility of language barrier and we non englishers use precise terminology when translating stuff. Majority of confusion comes from americans because of low desire for clear definitions. I'm in Europe and majority of tech talk is with germans. They dislike polymeaning words.
 
Nathan the Machinist said:
To be clear I'm talking about powered grinding with a CBN wheel. Not hand sharpening on a CBN (or diamond) stone.

My point being, any powered grinding can create an issue with heat. It doesn't matter if the wheel is aluminum. I'm speaking from (substantial) experience.
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There's the deviation. CBN talk started with sharpening and I continued on it.
 
Rick Marchand said:
The idea is to get the blade red hot before attempting to sharpen. That way, you are just pushing the molecules around to form an edge rather than removing molecules. The goal is to refine the apex to the width of one molecule. Then lock in the molecular structure by quenching it into an all-dressed potato(hold the chives). I feel the need to drive this home by saying "molecules" one more time.

Heh heh... Good post, Hoss. Most users, judge the quality of a knife by it's sharpness, edge retention and the type of steel it is made from. All of which mean nothing if the maker doesn't have an intimate knowledge of the mechanisms that govern those attributes. I will add my bit of advice.....

I cannot stress enough the importance of keeping that edge cool while sharpening. Lube, coolant, quality abrasives.... all will reduce heat build-up. Even hand sharpening on a dry diamond plate can overly temper the apex. This became surprisingly apparent to me, when I started making kitchen knives. I was a "220 belt, cork belt strop" guy when I was making choppers and camp knives. They were crazy sharp but I did not realize how much edge retention I was leaving on the table by my method. When I switched to setting my final edge with water stones and CBN plates (with plenty of water), I felt embarrassed.... don't tell the other guys, K?
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Damn right! This monkey knows what's up:

 
Maybe its your English translation program causing the problem since you are using German as the precise technical language. when I entered your term ...edge holding... into a couple of German language dictionaries I got the German word, Schneidhaltigkeit. Each definition referenced the cutting edges ability to retain its ability in "edge holding or retention". In other words... how long it remained sharp. Which was what DT was addressing on his original post.
Edge deformation ..formbestandigkeit. was not addressed in OP.
 
JoeBusic said:
What would the term be for the definition? Edge stability? Something else? Something has to be. There is a possibility of language barrier and we non englishers use precise terminology when translating stuff. Majority of confusion comes from americans because of low desire for clear definitions. I'm in Europe and majority of tech talk is with germans. They dislike polymeaning words.
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You should write a book on how to win friends and influence people.

Hoss
 
Mockery is a sign of weakness and incapability. Pulling the narrative away from intent are fascist tools to gain advantage over another as a result of excusability for selfworthlessness. Friends like those are destructive for one and are to be avoided.
Back to topic. Name the term for the definition. Cut the crap. Anyone smart here is waiting for the correct term now. I asked Larrin here to name it. If there is none, one should be made. It's kind of weird that the term doesn't exist. Or it exists and none of you know it.
 
JoeBusic said:
Mockery is a sign of weakness and incapability. Pulling the narrative away from intent are fascist tools to gain advantage over another as a result of excusability for selfworthlessness. Friends like those are destructive for one and are to be avoided.
Back to topic. Name the term for the definition. Cut the crap. Anyone smart here is waiting for the correct term now. I asked Larrin here to name it. If there is none, one should be made. It's kind of weird that the term doesn't exist. Or it exists and none of you know it.
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No one cares. None of the rest of us are having a problem with the terminology, only you. Let it go. It doesn’t matter.

I attended junior high school in the ‘70s where it was cool to have long hair and bell bottom jeans. One kid out of ~1500 students had an older mom that used to walk him to school (not cool), he wore a white shirt and tie every day (not cool), he was very smart but socially awkward. He used to tell us how weird we were.

Hoss
 
Gentlemen, let's try to take a moment, catch a breath and stick to the topic at hand. If we discuss the topic and not one another's faults and shortcomings, perhaps progress can be made.

We can't help with any confusion resulting from language barriers, but we can escort any members who cannot stick to the discussion (without blowing a gasket) from the room.

In simple American: Be nice to one another and keep personal comments to oneself.

Thank you.
 
Horsewright said:
Try Simple Green on your stones.

Many years ago I was involved in an experiment as sharpener and cutter, basically the muscle. Have a buddy that writes articles for outdoor magazines and he was working on an article about this. He has an extensive collection of custom knives from everybody you ever heard of back in the day. So I cut rope and I cut rope and I cut rope, 3/4” sisal rope to be exact. Literally by the trash can full and I don’t mean the one sitting at your desk but full sized contractor bag sized ones, and I cut rope and I cut rope. This was when there was this gem stone kinda sorta new way of forging (they said) and he’d been given a set of four of these pointy hard gemstone forged knives at a pig hunt where the knives had been introduced to the press. So he wanted to compare them to some other knives for this article. Anyhoo the protocol for this was I cut thin slices of rope with a 2x4 backer until the knife wouldn’t cut the rope. Then I hand sharpened it and cut until it wouldn’t cut, doing this three times. He scribed and took notes. I then belt sharpened the knife knocking the burr off on a buffer and cut till it wouldn’t cut and belt sharpened it again also going three times on each knife. We did this on a closet full of knives, some of mine included. They were all of similar size and grinds, apples to apples as much as possible. I wont tell ya all the details bout how I went through several 2x4s in three days, or how I filled up multiple contractor bags filled with cut up sisal rope. Or how my hand was so sore we were wrapping gauze around the handles and then vet wrap over the top of the gauze and I was wearing padded gloves, or how he bought the beer. Won’t bore you with the details but what I will tell you was there was absolutely no noticeable difference between hand sharpening and using the belt, none. Larrin and I discussed this here some years ago when I related this story another time for similar reasons. I too was surprised by the results cause before I made those eight gillion slices I would of told you that hand sharpening would be superior. What he said if I remembered correctly was that what we had proven was that done correctly, belt sharpening is certainly viable. Not superior but done correctly not inferior to hand sharpening either. What about those gemstone forged knives? Nothing specical there. Multiple knives out cut em, interestingly my friend had several of that companies regular D2 knives and every one of those out cut the gemstone forged ones. Anyhoo, I really haven’t hand sharpened since then. I kinda enjoy it but ole, achy, arthritic old hands say no.
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Thanks for relating that dave. Looks lime i will stick with 2x72 fir sharpening with a wet 400 grit belt on extra slow speed. It is *much* better for me for setting and holding a consistant angle (never could do that with stones…)
 
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