Massdrop- Diamond Stones

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memorael

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Well in the case of the steels I just mentioned, I would go with resin bonded diamond (I can't afford vitrified diamond). If not then SiC at the very least. I haven't tried cbn either.

My point was more along the lines that if you have a high hardness, high vanadium carbide steel. You are likely going to want to go with diamond stones if you want a clean apex. (Excluding CBN)
Yeah I agree on that, vanadium carbides as I understand are harder than most abrasives so unless you want a hole in your knife (a tiny one) diamonds and CBN are the way to go. I think the sigma power stones can abrade them but I can't confirm.
 

jwthaparc

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Yeah I agree on that, vanadium carbides as I understand are harder than most abrasives so unless you want a hole in your knife (a tiny one) diamonds and CBN are the way to go. I think the sigma power stones can abrade them but I can't confirm.
I've heard the sigma select are SiC. If so they should work. I've seen jeff jewel fo a sharpening with those type of steels with gritomatic SiC stones.
 

jwthaparc

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Barmoley

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Basically, it is not clear if it is harder. As you can see there is a hardness range so it might be same hardness or softer or slightly harder. It might cut or it might not or do it very slowly. Let's say it cuts slowly, that means you'll have to spend more time and the more time you spend the more chance you have to mess up the angle, etc. Just isn't the most efficient way to do it. CBN would be cool but there aren't many options unless you use a guided system so for steels like maxamet, k390, or maybe even hap40 class, diamonds are the most efficient and really most cost effective method if you take time and longevity into account.
 
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jwthaparc

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Basically, it is not clear if it is harder. As you can see there is a hardness range so it might be same hardness or softer or slightly harder. It might cut or it might not or do it very slowly. Let's say it cuts slowly, that means you'll have to spend more time and the more time you spend the more chance you have to measure the angle, etc. Just isn't the most efficient way to do it. CBN would be cool but there aren't many options unless you use a guided system so for steels like maxamet, k390, or maybe even hap40 class, diamonds are the most efficient and really most cost effective method if you take time and longevity into account.
Most definitely. I personally use my venev 240 through 1200 (sometimes 2000 but that one kinda sucks) on that class of steel. Although I will occasionally use my manticore for rough work, but that's a whole different deal because it's so much coarser than any carbide.
 

Barmoley

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Most definitely. I personally use my venev 240 through 1200 (sometimes 2000 but that one kinda sucks) on that class of steel. Although I will occasionally use my manticore for rough work, but that's a whole different deal because it's so much coarser than any carbide.
Yeah, coarse grids are not the problem, only once you get high enough in grid is where you can run into issues. I didn’t even realize there was a problem until I tried diamonds, knives seemed to get sharp, just didn’t stay sharp much longer than low alloy steels. Once I tried diamonds the difference was pretty drastic.
 

kayman67

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Been using cbn and diamonds for some years now. From my experience, a good progression to closed edges, always proved better, but even without one, diamond edges always performed better with most alloys. Same goes for stropping (pretty much with anything).
You guys might want to consider also these products for some higher grits at least CGSW 8" x 3" Resin Bonded Diamond
I know they are "just" resin bonds, but still.
Also, Practical sharpening has cbn plates, that could be used in a progression to a finer edge (I don't do this that much lately, but for a good amount of time I used to do the hard work with diamonds and move to cbn from 500 up).
 

inferno

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is there any good manufaturer of cbn plates/stones? that has a variety of grits?
 

kayman67

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As far as I know, just what's on Practical sharpening right now and those are from the only manufacturer left in Ukraine.
 

Barmoley

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Spyderco also has CBN plate with 2 grids. Reviews are pretty good.
 

Deadboxhero

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So let's say I'm going to sharpen something like s110v, k390, or maxamet. Which is going to be more likely to cause problems for the edge then? Aluminum oxide, or diamond stones?

If you don't mind indulging me on this question. Also if diamonds cause the problem, then what would the best option be cbn? Also like someone else said, is it even necessarily noticeable on something like a knife.
Alumina will, it is softer and doesn't cut the carbides, the burnishing causes stress on the harder carbides.
 

Deadboxhero

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I should also mention, it's well known in the optics world that diamond abrasives will cause micro-cracking.

I believe this link skips to the correct part, where he explains what diamonds do to a surface of a glass lens. Further on in the video, he removes the micro-cracks:

The modulus of elasticity of steel is not the same as glass, cutting steel is not the same as cutting glass even when steel is at 70rc.
 

Deadboxhero

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So a while back, the straight razor people started noticing that when using a DMT plate for bevel setting, chips would later form. So some mad scientist did this study about sharpening using diamonds and the conclusion is that diamonds will basically embed into the knife so deeply that the forces generated would crack the edge and form extremely tiny fissures that eventually would form a chip and depending on the hardness and material sometimes it would keep growing until it was visible. I would recommend using Diamonds for sharpening at very steep angles just to form an edge to save time but sometimes the risk is just to great when sharpening some of the higher HRC knives.
DMT has the abrasive grains essentially sitting on top of a plate, the abrasive grains are fully exposed and allowed to penetrate deeply into the bevel leaving a deeper scratch.

Deeper scratches and rougher finishes reduce edge stability.

Not all diamond stones are made like this.


So it's silly to say that diamonds universally cause problems.
 

Deadboxhero

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For kitchen knives it's not so bad in practice, unless you want super shallow angles like the guys in the straight-razor world.

If it makes you feel any better, high carbon steel knives often have micro-cracks inside the steel. It's one of the difficulties of forming martensite.


No, depends on how carbon rich the austenite is before quenching.

Putting +0.80% Carbon weight INTO Solution will create larger plates of martensite that smack into each other causing nanosized cracks. This very carbon rich martensite is also very brittle.

This is why heat treating high carbon Steels with blow torches and by eyeball is ridiculous, cannot control carbon in solution well and make a mechanically inferior product. Total **** show.


Only 0.60% carbon is needed in solution for maximum hardness of lath martensite without causing detrimental effects of retained austenite and more brittle plate martensite.
 
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Deadboxhero

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Thanks. I never read all the way to the bottom before 😅.

He didn't necessarily say SiC won't cut high vc steels. Just that it won't cut as well as diamond or cbn. If I'm understanding it.
The edges don't come up as crisp on high Vanadium high hardness steels, abrasive hardeness overmatch is better.

cBN and Diamond cut cleaner and the result is crisper at the apex.
 

Deadboxhero

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In my experience, it still happens. It has to do with stress concentrations formed by the super sharp edges on the diamonds.

Other abrasives are more prone to rounding over (blunting), and so their cutting action isn't so harsh. Diamonds tend to stay sharp, so they gouge out sharper grooves into the steel. The grooves are the main starting points for micro-cracks to seed - where lateral forces get concentrated.

On the flip side, diamond abrasives gouging out deep scratches are what we like about them. They work fast and form a toothy edge.
You're making it sound like softer abrasives don't have consequences as well, The problem with soft abrasives is that the duller smoother grains burnish and deform the metal rather than remove. Deformed metal means more strain. This is magnified when we get larger volumes of harder carbide with a harder matrix.

As far as surface roughness,
moving to a finer grit with a bonded cBN/Diamond cleans things up If desired or needed, meanwhile burnishing is just burnishing.
 

memorael

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DMT has the abrasive grains essentially sitting on top of a plate, the abrasive grains are fully exposed and allowed to penetrate deeply into the bevel leaving a deeper scratch.

Deeper scratches and rougher finishes reduce edge stability.

Not all diamond stones are made like this.


So it's silly to say that diamonds universally cause problems.
Everything you've said sounds really nice on paper, in practice I still see cracks forming when using diamonds, but whatever if you want to keep using diamonds for whatever reason go ahead. I find you calling me silly a bit uncivilized since all I did was respectfully mention what can and has happened, it sparked some debate and everyone got smarter or debated their point of view.
 

Deadboxhero

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Everything you've said sounds really nice on paper, in practice I still see cracks forming when using diamonds, but whatever if you want to keep using diamonds for whatever reason go ahead. I find you calling me silly a bit uncivilized since all I did was respectfully mention what can and has happened, it sparked some debate and everyone got smarter or debated their point of view.
"It" is not the same as "you're"

"It is silly to say that diamonds universally cause problems"
 

Deadboxhero

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Diamond was used to make this edge. No chipping with extreme geometry and hardness on high carbide stainless was observed with edge stability testing.


Diamond was used to make this edge,

No blowout with flexing M398 on brass


Diamond and CBN used on 15v, batoning a 16d nail with 15v at 67rc and 23% Vanadium carbide volume.





Everything you've said sounds really nice on paper, in practice I still see cracks forming when using diamonds, but whatever if you want to keep using diamonds for whatever reason go ahead. I find you calling me silly a bit uncivilized since all I did was respectfully mention what can and has happened, it sparked some debate and everyone got smarter or debated their point of view.
 

RDalman

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Diamond was used to make this edge. No chipping with extreme geometry and hardness on high carbide stainless was observed with edge stability testing.


Diamond was used to make this edge,

No blowout with flexing M398 on brass


Diamond and CBN used on 15v, batoning a 16d nail with 15v at 67rc and 23% Vanadium carbide volume.
All of those edges are thick and not relevant to kitchenknives or razors imo.
 

Barmoley

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I haven't noticed any chipping when using vitrified or resin diamond stones on high carbide, high hardness kitchen knives. I don't look at edges under a microscope so I don't know if micro fractures exist. What abrasive would be suggested if not diamonds? Diamonds seem to leave the best, longest lasting edges as compared to SiC, or aluminum oxide which don't work very well in my experience on high hardness, high carbide steels. CBN would be interesting to try since it supposed to be gentler due to its shape, but CBN bench stones are not really available. There are some plates available, but from all accounts they feel similar to diamond plates when sharpening.

Has anyone who uses vitrified or resin diamond stones to sharpen their kitchen knives actually seen any extra chipping as compared to using other abrasives?
 

Sparten007

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Been wanting some for awhile 👍🏽
 

Kippington

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You're making it sound like softer abrasives don't have consequences as well, The problem with soft abrasives is that the duller smoother grains burnish and deform the metal rather than remove. Deformed metal means more strain. This is magnified when we get larger volumes of harder carbide with a harder matrix.

As far as surface roughness,
moving to a finer grit with a bonded cBN/Diamond cleans things up If desired or needed, meanwhile burnishing is just burnishing.
With this thread title in mind, I wondered why you wanted me to concentrate on the negatives of other abrasives so much... then I realised you must be the guy selling the diamond stones. Makes sense now.
I don't have a horse in this race.

No, depends on how carbon rich the martensite is before quenching.

Putting +0.80% Carbon weight INTO Solution will create larger plates of martensite that smack into each other causing nanosized cracks. This very carbon rich martensite is also very brittle.

This is why heat treating high carbon Steels with blow torches and by eyeball is ridiculous, cannot control carbon in solution well and make a mechanically inferior product. Total **** show.


Only 0.60% carbon is needed in solution for maximum hardness of lath martensite without causing detrimental effects of retained austenite and more brittle plate martensite.

If the gentleman in the video addresses microcracking in a 0.34% w C steel, no offence but I'm trusting his word over yours. He ain't exactly the kind of guy whose concerns you dismiss, on the subject of metallurgy.

 

memorael

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Ah, so this gentleman sells diamond stones, makes sense now why he's pushing the diamond hones.

I want to make my point clear, I use and like diamond stones, they are a tool and I use them when the balance of risks vs benefits shifts in a favorable way. All I wanted to point out is that Diamonds are known by experience and through some un professional or professional study (can't confirm here) that they can and will in some cases cause micro cracks, as I recall the stones used in these cases where metal plates with diamonds embedded into them. When someone used matrix type diamond hones I recall something happened to the tune of diamonds getting loose and rolling into the steel, but I don't remember if there is any bad effect.

So if you have a knife that get's an edge you like after using a diamond hone, hey more power to you.
 

memorael

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Diamond was used to make this edge. No chipping with extreme geometry and hardness on high carbide stainless was observed with edge stability testing.


Diamond was used to make this edge,

No blowout with flexing M398 on brass


Diamond and CBN used on 15v, batoning a 16d nail with 15v at 67rc and 23% Vanadium carbide volume.
All these videos proove is that the knife is sharp, and that the steel has a good heat treatment. I can do the same with a king 1k on a good knife.
 

kayman67

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They prove that not all diamond sharpening approaches, by default, will damage the edge, at least not to the extent to start part of the apex fly under extreme usage/pressure. So what's the debate about? I have many years of experience with this. For some reason, those edges perform longer and better when this should be impossible, no? Lately, the question is why. I see a good amount of effort trying to prove this wrong on a very micro level, but the real life results are what they are. What do we do with them?
Anyway, scienceofsharp, even if I feel like something's missing there, proved that some cracks are present to some degree with both classes of abrasives, not just diamonds.
 

Kippington

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Anyway, scienceofsharp, even if I feel like something's missing there, proved that some cracks are present to some degree with both classes of abrasives, not just diamonds.
His most recent article? My take-away was that diamonds tend to crack carbides, moreso than other abrasives which left carbides standing proud. Interesting you saw it a different way.

www.scienceofsharp.com
 

Barmoley

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You guys are totally off base questioning Shawn‘s integrity just because he happens to sell diamond stones. He has very extensive experience in sharpening and working with all sorts of high wear, high hardness, high carbide steels and he uses what works for him. He’s worked with materials that very few here if any have worked with. You might disagree with his conclusions or reasons, but to assume that he would promote diamonds just because he sells them is absolutely uncalled for and just isn’t cool at all.
 

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