# when the abrasive can't cut the carbides.



## inferno (Feb 26, 2020)

found a new article on https://scienceofsharp.com/2019/11/03/carbides-in-maxamet/

i found it quite interesting.
this is a pic of high carbide blade ground on diamonds. and stropped on 1micron diamond paste.






deburred/stropped on glass 8k. and then all those carbides show themselves





same edge after light use





same edge after heavy use





another diamond ground edge but stropped on a jnat. lower mag though






higher mag of the jnat stropped edge





many people discuss if high carbide steels are better handled by diamonds stones. and its quite obvious that this is the case if you want a clean edge. but to me it seems the high carbide steels will retain to that "sharpened on non diamond media" even after heavy use. where only the actual carbides are sticking out and the matrix gets abraded. 
and i'm guessing this would happen even if you began with a "clean" diamond edge.

so is there then a point to sharpening on diamonds? talking final edge here. not the heavy lifting.
cool article imo!


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## BarryMM (Feb 26, 2020)

The guy from knifegrinders australia is a very strong believer in diamonds and cbn wheels for the Tormek he uses in his sharpening shop. Those images show he's probably right. He also does his burr removal with diamond paste. Those carbides are harder than stone so diamonds are a sharpeners best friend


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## inferno (Feb 26, 2020)

yeah but what happens after some use? and does it then matter if you used diamond or alox/sic in the first place?

cr-carbide is softer than alox.
also iron carbide (cementite) is softer than alox.

then i dont think there is any other carbide thats softer than alox. nor nitride.


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## inferno (Feb 26, 2020)

also that above was stropped on diamond paste. diamond plates works completely different to what one might think.

https://scienceofsharp.com/2015/03/01/the-diamond-plate-progression/

dmt 325





dmt 600




dmt 1200




dmt 8k





atoma 400


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## vicv (Feb 26, 2020)

I'm of the camp that diamonds are unnecessary regardless of the steel. If you like the way diamonds work for you then by all means. I'm not interested in cutting the carbides. They're so much smaller than the abrasive particles I use it's a moot point. Now if I wanted to sharpen rex 121 to a true .5 micron I guess it might matter but that's never going to happen. Those steels do best with 300-400 grit edges. For that a sic stone works just fine


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## kayman67 (Feb 27, 2020)

The guys in the pocket knives communities did extensive tests for this and every single time the diamond approach was better. Since this was for all of them, something is definitely going on.
If I remember this right, Michael Christy was one of the latecomers and this happened after doing some real life edge comparisons for months. He's a very reliable sharpener in terms of edge consistency. He got the same differences over and over. 
For something like CPM REX 121, would be almost impossible to sharpen with something else anyway. I use diamonds or cbn. I have a variety of sic low grit stones that would eat M390 for breakfast, but don't work with 121. I haven't tried them with Maxamet though. At some point, some years ago, BBB also talked about how the wrong sharpening medium for Maxamet would make such a difference that would render the alloy useless. I just didn't have the time or need to mess with it. He also advocates, based on experience, for diamonds. 
I think Cliff Stamp had similar ideas about other alloys and sharpening medium, as well, but he was much more detailed with differences between mediums. This on its own would be a great topic maybe. 
So, if it's a direct interaction or just something easier to use to such an extent that guys would experience better results, it's hard to say. Would it matter? Technically, yes. In real life, hard to say. I actually put an equal between them as at this point as results just matter more and I can't really recommend something else, can I?
As a side note, there's definitely some truth about how coarse edges perform better here, but it's not always as coarse as one might think. You just need a proper refinement. For example, on Maxamet, BBB had best possible edges around 3-4k diamond based stones. That's way far from 3-400 grit range with diamonds. And there was a definitive improvement in sharpness as well. I had some killer edges with 121 after cbn 4-5k as well, but they are just very hard to obtain. And this is the problem for most people with kitchen knives and why some simple stuff is way more appealing. It's way easier to get results. You don't need to be really good and have only the right tools for the job to see a difference.
These days, because of makers like Venev and EdgePro, I've seen an increasing number of people going for mirror edges, with proper stones. It wasn't always the case in the past. And the performance is still there. Well, some guys had some of them polished as well in the past, but there was a ton of work involved and a great deal of experience. Now seems like it got a lot more approachable.


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## vicv (Feb 27, 2020)

I've had conversations with BBB before about this stuff and we do not agree. I do not believe he is the foremost expert on this stuff. Neither is Mr Christy. I've sharpened maxamet at 71hrc with my Norton crystolon stones and it worked great. No issues and steel was not left useless.


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## Barmoley (Feb 27, 2020)

vicv said:


> I've had conversations with BBB before about this stuff and we do not agree. I do not believe he is the foremost expert on this stuff. Neither is Mr Christy. I've sharpened maxamet at 71hrc with my Norton crystolon stones and it worked great. No issues and steel was not left useless.


Did you compare the same knife sharpened on diamonds or cbn?


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## kayman67 (Feb 27, 2020)

vicv said:


> I've had conversations with BBB before about this stuff and we do not agree. I do not believe he is the foremost expert on this stuff. Neither is Mr Christy. I've sharpened maxamet at 71hrc with my Norton crystolon stones and it worked great. No issues and steel was not left useless.



Well, I've seen that most of the time we have similar experiences. This can be a point of view, as they talk about what performance can be achieved in real life usage comparing different sharpening paths. So maybe "useless" is too harsh, but this was mostly coming from the community struggling with Maxamet. Since so many got the same results and I haven't tested on Maxamet for myself, hard to argue with either really. With CPM REX 121 is a different story.


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## vicv (Feb 27, 2020)

Fair enough different people have different experiences


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## Barmoley (Feb 27, 2020)

kayman67 said:


> Well, I've seen that most of the time we have similar experiences. This can be a point of view, as they talk about what performance can be achieved in real life usage comparing different sharpening paths. So maybe "useless" is too harsh, but this was mostly coming from the community struggling with Maxamet. Since so many got the same results and I haven't tested on Maxamet for myself, hard to argue with either really. With CPM REX 121 is a different story.


I remember these discussions, I think "useless" was meant as benefits of maxamet are lost because people couldn't sharpen these correctly. Only when they started using diamonds and cbn they started seeing maxamet far outperforming "common" alloys. One could argue this was because of lack of sharpening skill, but when enough people see similar results there might be something to it. Could just be that diamonds do it quicker so edges are more consistent, hard to say without someone running some real tests cough @Larrin cough


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## kayman67 (Feb 27, 2020)

Yeah, losing benefits is something experienced with kitchen knives, too, due to poor sharpening and maintenance.


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## Desert Rat (Feb 27, 2020)

It's this kind of stuff that has brought me to this forum. I have resisted buying knifes because I don't know if I can sharpen the newer steels with the stones I prefer.


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## M1k3 (Feb 27, 2020)

Desert Rat said:


> It's this kind of stuff that has brought me to this forum. I have resisted buying knifes because I don't know if I can sharpen the newer steels with the stones I prefer.



You can always just buy more knives that aren't any of the high vanadium/tungsten type to make up for edge retention.


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## Larrin (Feb 27, 2020)

Most any stone will work with high vanadium PM steels in the lower grits. The abrasive is larger than the carbides so it all gets removed together. At finer grits the softer abrasives are much slower because they can’t abrade the carbides.


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## Desert Rat (Feb 27, 2020)

Larrin said:


> Most any stone will work with high vanadium PM steels in the lower grits. The abrasive is larger than the carbides so it all gets removed together. At finer grits the softer abrasives are much slower because they can’t abrade the carbides.


There are different kinds of carbides though right or does it not matter and the natural stones will have issues with all of them?


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## vicv (Feb 27, 2020)

With the coarser stones you're just abrading the steel matrix. The carbides go along for the ride. Yes more wear resistant steel will resist the abrasives more. But normal stones still work. When people blame the equipment it's because they don't have the skill. And there's no offense meant there. I've been there


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## Larrin (Feb 27, 2020)

Desert Rat said:


> There are different kinds of carbides though right or does it not matter and the natural stones will have issues with all of them?


There are different carbides and different abrasives and each come in a range of hardnesses. Iron carbides are pretty soft, for example, compared to vanadium carbides.


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## kayman67 (Feb 28, 2020)

vicv said:


> With the coarser stones you're just abrading the steel matrix. The carbides go along for the ride. Yes more wear resistant steel will resist the abrasives more. But normal stones still work. When people blame the equipment it's because they don't have the skill. And there's no offense meant there. I've been there



This is the yes and the no. 
If you look at SEM images, sometimes all that you get is, at best, some rounding. So not even tear out carbides.
What makes this somewhat difficult, is the need to be very specific. Sometimes there's some cutting, but it's so slow, that inconsistencies are becoming an issue. Here I agree with you. The better the skill, the lesser the problem, with specific combos in mind. 
But what happens when the edge would take shape? A few years ago was some testing done with Elmax. Now, at first glance, Elmax doesn't look like something all that special. If you ever sharpened any, this might be a surprise just as big as it was back then. Aluminium oxide and diamonds got the alloy just as sharp. That initial result was very misleading. Thing is, the edge retention was 3 or 4 times better with diamonds. The test used some kind of jig with measurements to sharpen and some other machine to measure sharpness, so human variables were not an issue. But even on something as common as S30V, there was a noticeable impact on edge retention. Not really huge as before, but it was there. Does it matter? Would it make a difference for everyone? Hard to say. As a principle, yes. In other regards, maybe not. Because you don't really see people struggling with S30V that much. For me, this matters with stuff like CPM REX 121. 
And there's something else. Someone told me that he doesn't care about edge retention. If the knives won't cut, he will sharpen them and that's that. The easier it is, the better. He considered that we invest too much into it. 
This makes for a very problematic general answer, as there is none that could be definitive. 
As far as carbide tear out is concerned, this was talked to oblivion countless times. I don't think we can add anything.


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## Larrin (Feb 28, 2020)

I would be very skeptical of a result saying Elmax is 3-4x better with diamonds. Elmax has very little vanadium carbide. It’s more likely that the edge was significantly different in terms of sharpness or finish.


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## kayman67 (Feb 28, 2020)

That's why it was so unexpected. Really an alloy that would pass unnoticed. Well, sort of, anyway, since some people back then were advocating for differences starting at 3-4%, where I think Elmax is at the lower end, so technically would still qualify. But the difference was there for all of them, just not that obvious. 
Wouldn't it be highly unlikely that so many people, doing tests that are so different, to have more or less similar experiences and all be completely wrong?


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## Larrin (Feb 28, 2020)

kayman67 said:


> That's why it was so unexpected. Really an alloy that would pass unnoticed. Well, sort of, anyway, since some people back then were advocating for differences starting at 3-4%, where I think Elmax is at the lower end, so technically would still qualify. But the difference was there for all of them, just not that obvious.
> Wouldn't it be highly unlikely that so many people, doing tests that are so different, to have more or less similar experiences and all be completely wrong?


It is not just the amount of vanadium but also other elements. The high chromium in Elmax means its vanadium carbide is less.


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## kayman67 (Feb 28, 2020)

I've put a Tur on my list for some Elmax testing, just for fun. I hope I'll get to it someday. I have a damn long list with stuff to buy and try.


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## vicv (Feb 28, 2020)

I was not involved in those conversations but I have seen extensive testing and silicon carbides works as well as anything else. With the work done by Phil Wilson and Jim "Ankerson" on blade forums. When you can get ~2200 cuts on 5/8 rope and still slice paper afterwards I feel that works just fine


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## Larrin (Feb 28, 2020)

vicv said:


> I was not involved in those conversations but I have seen extensive testing and silicon carbides works as well as anything else. With the work done by Phil Wilson and Jim "Ankerson" on blade forums. When you can get ~2200 cuts on 5/8 rope and still slice paper afterwards I feel that works just fine


Silicon carbide has similar hardness to vanadium carbide, and both of those men use coarse edges since they perform better in slicing. Therefore good performance is expected. I don't know whether edge retention would be affected at fine grits but I wouldn't expect a difference at coarse grits.


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## vicv (Feb 28, 2020)

That's my point Larrin. If I need a knife for push cutting I'm not choosing maxamet..... That being said what the OP linked to at the beginning of this thread shows carbide tearout isn't a thing the matrix holds it well. So I can't see that it matters whether the abrasive can cut the carbides at high grit Edge retention should be the same if the sharpening was the same. Now at high grits will sic cut as well and get as fine......I don't know. But in my opinion it's a moot point


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## kayman67 (Feb 28, 2020)

Hard to answer. On one side, just too many people taking things from A to B and getting similar results. On the other, I can't prove myself that one way is better than the other for something like Elmax or Maxamet. I just take the general experience.
And maybe the perspective should be from a different standing point of view. If you look at some tests Larrin did, with a toothy edge if I remember correctly, these alloys were still better, right? Meaning you can't level out any alloy with a sharpening method as eventually some are still better performers.
So, the only debate would be this: if there would be a way to keep the performance and still have a better/desired edge, wouldn't it be good practice at least to use that method with any alloy?
I know BBB showing, at some point, just how well Maxamet could retain its edge and how effortlessly would push cut. Obviously, we talk about Maxamet as it just popped into my head then. And Michael did the same a couple of years later. I only mentioned him as he kinda discovered things on his own, while using the knives and looked into it for some time after. Right now, with stuff from EdgePro and Venev, things got a lot easier from what I've seen.
I'm not saying that diamonds made SiC vestigial or anything, but pushing things in one direction just to prove that something would work to some extent, ignoring that something else could be a better path for all aspects, is not helping either. 
I do have a good number of silicon carbide and aluminum oxide stones (great stones actually, that are very hard to find these days so my interest in them is there) and I really like them when it makes sense to be used. While on M390 worked like a charm, didn't on 121. There's no real bias towards anything.


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## Larrin (Feb 28, 2020)

I would prefer if more companies were exploring bonded CBN and diamond stones since they seem to offer the best of both worlds in many cases. The diamond plate stones leave a coarser scratch pattern than their grit would indicate while the traditional abrasives are not hard enough for vanadium carbides. Perhaps the price of diamond and CBN bonded stones would go down if there was more competition there.


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## inferno (Feb 28, 2020)

i think one of the problems with the metal bond/resin bond diamond and cbn is that the grit rating does not correspond well to japanese waterstones. i read something on BF a a week or 2 back where some abrasive manufacturer had done a study with vitrified/plated/resin/metalbond etc. abrasives. and there is a big difference between these technologies regarding resulting surface finish and material removal speed. even though all technologies could be the "same grit"

another problem with the newer breed of metal/resin stones is they use micron, fepa f, ansi, mesh, grit etc etc. and its a lottery what you are actually buying. with the japanese stones a 1k is a 1k (more or less). thats it. you know what you get. and i also think jis is the defacto only standard for bench sized water stones.

then there are problems with the stones clogging up or getting smooth. so you have to refresh the surface somehow. and from what i have read this is at least a bit problematic with the metalbond stones.

all these 3 problems would need to be solved/cleared up before this can take off imo. and if you read up on BF where these stones are popular there is no consensus if they are fast stones, good, hard, soft, cloggy etc etc, since very few there has any experience with regular waterstones from the most common quality brands.

Maybe the best option would be to simply substitute half of the abrasive in the regular stones with diamond or cbn, and then change nothing. 
inagine this: shapton ice-stone, light blue colored, 3mm abrasive, just like a glass stone but with 50% diamonds


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## vicv (Feb 28, 2020)

Honestly no change would be needed. Replace the alox grit with diamond. Done


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## inferno (Feb 28, 2020)

btw i have had good luck with regular glass and pro and naniwa pro, on skd11 (d2), r2, srs-15. sure these are not 10%V or W but they are in the "exotic" category imo.

up to 1k or so i think almost all steels feel similar on the stones, and they are just as slow/fast to work, if they are similar hardness. maybe white/blue is a bit faster.

r2 i have no problem taking up to 8k on glass. just did one last week on the 4k the edge gets super good. its just slower than lower alloyed steels.
srs15 same as r2 imo.

skd i have taken to 12k on the shapton pro, no problem at all. it got so sharp i was a bit afraid of it actually lol, truly scary sharp. and it felt just like any other hard steel getting there. sure d2 is below 1%V so thats probably why. but its still 1,5%C and its full of carbides.


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## inferno (Feb 28, 2020)

vicv said:


> Honestly no change would be needed. Replace the alox grit with diamond. Done



it would be to expensive if they did that. but if they only did half or maybe even 10% would be enough, then the cost would not be much more than now.


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## inferno (Feb 28, 2020)

i wonder what the profit % is on stones in general. it must be astronomic. i mean one can buy alox sandblasting powder in 25kg bags quite cheap.


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## inferno (Feb 29, 2020)

found the thread about the bond types. 
i interpret the surface roughness as at least somewhat related to material removal rate in this graph. 
and as we all can see resin with 60 mesh equals "metal" 500. and thats a big ****ing problem imo. its a 8x difference with this parameter. its not an apples/oranges comparison anymore, its more like comparing apples and poetry written by a block of asphalt. what if i told you your knife could have a +-4X edge holding capacity. would you buy that? could be really good right...







https://www.asahidia.co.jp/eng/wp-content/uploads/2015/05/B02.pdf
https://www.bladeforums.com/threads...d-type-on-finished-surface-roughness.1706791/


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