Community Sharpening Journal

[JD Spydo]

Speaking of diamond stones have any of you here ever tried any of the diamond sharpening stones made by 3M? I've got a couple of their stones that I bought from Texas Knifemaker Supply quite a while ago and I've just had excellent luck with both of them. However you don't hear much of anything said about the 3M diamond stones on any of these forums. :confused:
I have the "coarse" and "extra-coarse" and they do just as good as the Norton diamond stones I have.

I've also got some diamond files made by 3M and they are really good as well.

[Pelagic]

I'm curious about Trend as well. Woodworkers seem to really like Trend diamond plates for sharpening chisels.

[Doeswhateveraspidercan]

Just found the info I was looking for. In order to sharpen carbides and not just pull them out with the steel or round them with abrasives larger than they are you need abrasives smaller than they are.

Most carbides fall between 2 and 4 Microns. So this translates to me as using a strop with Diamond paste or spray of 1 micron.

[vivi]

Speaking of diamond stones have any of you here ever tried any of the diamond sharpening stones made by 3M? I've got a couple of their stones that I bought from Texas Knifemaker Supply quite a while ago and I've just had excellent luck with both of them. However you don't hear much of anything said about the 3M diamond stones on any of these forums. :confused:
I have the "coarse" and "extra-coarse" and they do just as good as the Norton diamond stones I have.

I've also got some diamond files made by 3M and they are really good as well.

JD I searched their site and didn't see the stones you mentioned.

[Deadboxhero]

Just found the info I was looking for. In order to sharpen carbides and not just pull them out with the steel or round them with abrasives larger than they are you need abrasives smaller than they are.

Most carbides fall between 2 and 4 Microns. So this translates to me as using a strop with Diamond paste or spray of 1 micron.

Nah, most Carbides are larger, 10um ranges like in PM stainless (20cv,M390) at high volume, non PM stainless at lower volume will have areas of very large clusters(n690co) even bigger unless volume is low like AEB-L. Vanax was the exception with 13% volume and very fine Nitrides thanks to the Nitriding process forming them at lower temps not allowing them to grow.

You can look through the micrograph article and measure the Carbides with the 20um key on the bottom right.

[Deadboxhero]

Speaking of diamond stones have any of you here ever tried any of the diamond sharpening stones made by 3M? I've got a couple of their stones that I bought from Texas Knifemaker Supply quite a while ago and I've just had excellent luck with both of them. However you don't hear much of anything said about the 3M diamond stones on any of these forums. :confused:
I have the "coarse" and "extra-coarse" and they do just as good as the Norton diamond stones I have.

I've also got some diamond files made by 3M and they are really good as well.

Just not very competitive, they don't offer anything unique or any advantages to what's available from Venev, Japanese Knife Imports, Naniwa, Practical Sharpening, Diamond Matrix etc.



You can get more performance for less.

[Doeswhateveraspidercan]

Just found the info I was looking for. In order to sharpen carbides and not just pull them out with the steel or round them with abrasives larger than they are you need abrasives smaller than they are.

Most carbides fall between 2 and 4 Microns. So this translates to me as using a strop with Diamond paste or spray of 1 micron.

Nah, most Carbides are larger, 10um ranges like in PM stainless (20cv,M390) at high volume, non PM stainless at lower volume will have areas of very large clusters(n690co) even bigger unless volume is low like AEB-L. Vanax was the exception with 13% volume and very fine Nitrides thanks to the Nitriding process forming them at lower temps not allowing them to grow.

You can look through the micrograph article and measure the Carbides with the 20um key on the bottom right.

Interesting do you have a link to this article?

I sourced my info from these two sources one of them being Crucible themselves where they plainly call out carbide size between 2 and 4 microns seems to me like I am missing something here.

https://www.bladeforums.com/threads/car ... s.1421130/

From Crucible

http://www.crucible.com/eselector/gener ... part1.html

" The CPM Process

In order to manufacture tool steels with high wear resistance, without encountering these serious drawbacks, powder metallurgy processes are used to produce P/M tool steels having high vanadium content. Molten tool steel is atomized into fine droplets which solidify from the liquid so rapidly that the carbides are prevented from forming into large segregated networks. The solidified droplets form powder, which is then loaded into a steel can and consolidated (the individual powder particles are bonded together under high pressure), and subsequently forged or rolled into steel bars. The carbides formed during the extremely rapid solidification are fine in size (2 to 4 microns), and are uniformly distributed throughout the microstructure. Compare this to the larger carbides (up to 50 microns or more in size), and the characteristic alloy segregation or banding which results from conventional steelmaking methods. The characteristic feature of P/M tool steels is their near complete freedom from carbide segregation."

[Deadboxhero]

Just found the info I was looking for. In order to sharpen carbides and not just pull them out with the steel or round them with abrasives larger than they are you need abrasives smaller than they are.

Most carbides fall between 2 and 4 Microns. So this translates to me as using a strop with Diamond paste or spray of 1 micron.

Nah, most Carbides are larger, 10um ranges like in PM stainless (20cv,M390) at high volume, non PM stainless at lower volume will have areas of very large clusters(n690co) even bigger unless volume is low like AEB-L. Vanax was the exception with 13% volume and very fine Nitrides thanks to the Nitriding process forming them at lower temps not allowing them to grow.

You can look through the micrograph article and measure the Carbides with the 20um key on the bottom right.

Interesting do you have a link to this article?

I sourced my info from these two sources one of them being Crucible themselves where they plainly call out carbide size between 2 and 4 microns seems to me like I am missing something here.

https://www.bladeforums.com/threads/car ... s.1421130/

From Crucible

http://www.crucible.com/eselector/gener ... part1.html

" The CPM Process

In order to manufacture tool steels with high wear resistance, without encountering these serious drawbacks, powder metallurgy processes are used to produce P/M tool steels having high vanadium content. Molten tool steel is atomized into fine droplets which solidify from the liquid so rapidly that the carbides are prevented from forming into large segregated networks. The solidified droplets form powder, which is then loaded into a steel can and consolidated (the individual powder particles are bonded together under high pressure), and subsequently forged or rolled into steel bars. The carbides formed during the extremely rapid solidification are fine in size (2 to 4 microns), and are uniformly distributed throughout the microstructure. Compare this to the larger carbides (up to 50 microns or more in size), and the characteristic alloy segregation or banding which results from conventional steelmaking methods. The characteristic feature of P/M tool steels is their near complete freedom from carbide segregation."

I'm aware of the literature.
However there is always another level of complexity to things.

https://knifesteelnerds.com/2019/05/26/ ... fe-steels/

Dig in

[ekastanis]

https://knifesteelnerds.com/2019/05/26/ ... fe-steels/

Looking again at the metallographs for the PM stainless steels in particular, the characteristic length scale of the carbide particles appears very consistent with Crucible's stated 2 - 4 μm. Certainly (e.g. especially with 20CV) there are some agglomerates which have a major dimension on the order of 10 μm, but generally the size of the precipitated particles is around half an order of magnitude smaller.

[Pelagic]

I don't worry about carbides much in sharpening. I just think if them as something that helps working edge lifetime. I know that's an oversimplification but oh well. I'd rather have a finely structured, hard, strong matrix of low carbide volume than a softer steel loaded with carbides. And it has only a small/moderate impact on the edge I give the blade.

[Deadboxhero]

https://knifesteelnerds.com/2019/05/26/ ... fe-steels/

Looking again at the metallographs for the PM stainless steels in particular, the characteristic length scale of the carbide particles appears very consistent with Crucible's stated 2 - 4 μm. Certainly (e.g. especially with 20CV) there are some agglomerates which have a major dimension on the order of 10 μm, but generally the size of the precipitated particles is around half an order of magnitude smaller.

Yes, but the characteristics and behavior will be
held back by the largest sized connected clusters.

[Doeswhateveraspidercan]

Just found the info I was looking for. In order to sharpen carbides and not just pull them out with the steel or round them with abrasives larger than they are you need abrasives smaller than they are.

Most carbides fall between 2 and 4 Microns. So this translates to me as using a strop with Diamond paste or spray of 1 micron.

Nah, most Carbides are larger, 10um ranges like in PM stainless (20cv,M390) at high volume, non PM stainless at lower volume will have areas of very large clusters(n690co) even bigger unless volume is low like AEB-L. Vanax was the exception with 13% volume and very fine Nitrides thanks to the Nitriding process forming them at lower temps not allowing them to grow.

You can look through the micrograph article and measure the Carbides with the 20um key on the bottom right.

Interesting do you have a link to this article?

I sourced my info from these two sources one of them being Crucible themselves where they plainly call out carbide size between 2 and 4 microns seems to me like I am missing something here.

https://www.bladeforums.com/threads/car ... s.1421130/

From Crucible

http://www.crucible.com/eselector/gener ... part1.html

" The CPM Process

In order to manufacture tool steels with high wear resistance, without encountering these serious drawbacks, powder metallurgy processes are used to produce P/M tool steels having high vanadium content. Molten tool steel is atomized into fine droplets which solidify from the liquid so rapidly that the carbides are prevented from forming into large segregated networks. The solidified droplets form powder, which is then loaded into a steel can and consolidated (the individual powder particles are bonded together under high pressure), and subsequently forged or rolled into steel bars. The carbides formed during the extremely rapid solidification are fine in size (2 to 4 microns), and are uniformly distributed throughout the microstructure. Compare this to the larger carbides (up to 50 microns or more in size), and the characteristic alloy segregation or banding which results from conventional steelmaking methods. The characteristic feature of P/M tool steels is their near complete freedom from carbide segregation."

I'm aware of the literature.
However there is always another level of complexity to things.

https://knifesteelnerds.com/2019/05/26/ ... fe-steels/

Dig in

Digging in :)

Ah, thank you, I never noticed the UM in these pictures before and after a quick search understand 1 UM is the same thing as 1 Micron. Clearly this shows one must adjust ones abrasives to the steel and its carbides being sharpened.

Looking at this chart here is what I am perceiving as pure guess work and am listing below based on interest I have due to ownership. Also from the article the primary type of carbide present which should determine the abrasives that can be effectively utilized.

Z-Wear/CPM-CruWear (1975°F) – 10% carbide volume looks like 3 to 5 Microns primarily Chromium with a little less than half vanadium

LC200N/Cronidur 30/Z-Finit (1905°F) 3 microns Primarily Chromium.

S30 V not shown in the article close to the same as S35Vn minus the Niobium carbides.

S35VN (1975°F) – 14% carbide volume 5 to 8 Microns combination of mostly chromium and vanadium carbides wit a little Niobium

Elmax (1975°F) – 19% carbide volume 8 to 10 Microns combination of mostly chromium and vanadium carbides

XHP (1950°F) – 21% carbide volume 10 to 12 Microns primarily made up of chromium carbides

S90V (2050°F) – 21% carbide volume 8 to 10 Microns combination of chromium and vanadium carbides high concentrations of both

20CV (2140°F) – 22% carbide volume 8 to 10 Microns combination of chromium and vanadium carbides Mostly Chrome.

This all leads me to understand better why Alumina is not the best abrasive for use with steels with vanadium content as the higher it is the higer it has been in my experience to get sharp compared to steel like cruwear that is mostly Chromium carbides and also holds true with M4 and LC200N.



According to this https://www.reade.com/reade-resources/r ... -abrasives

Vanadium is at 9-9.5 on the Mohs hardness scale

Chromium is at 8 to 8.5 on the Mohs harness scale

Tungsten Carbide is at 9.0

Alumina (Synthetic aluminum oxide) 3.4 on the Mohs hardness scale

Corundum (Natural aluminum oxide) 9

Aluminum oxide 9

Diamond is at 10 and from what I can tell so is CBN

So when we look at this it is pretty easy to see if we are using anything less than Diamond or CBN trying to sharpen these High carbide steels with either Tungsten or Vanadium present we are fighting an up hill battle using Abrasives that are equally or less hard than the materials we are encountering.

This goes along way towards explaining why some steels are more difficult to get to a truly sharp edge than others and why grit matters we have to get lower in microns than the size of the carbides to effectively sharpen the carbides as well as the steel and we need a substance that is harder than the carbides and smaller to sharpen them properly.

My conclusion then is the accepted axiom of the coarse edge being better for high carbid content steels may be true in one way but also false in another.

In order to get the best out our sharpening efforts that we should probably consider sharpening abrasives made of Diamond or CBN only and also as a nice median figure lets say weigh in at 3 microns as the final grit used in order to shape the Carbides and not leave them rounded or just pulled out with the steel.

Spyderco Diamond Rods = 40 Micron = 443.19 Grit

Spyderco Brown Rods Synthetic Alumina = 15 Micron = 1252.881 Grit

Spyderco fine white rods Synthetic Alumina= 6 Micron = 3307.740 Grit

Spyderco Ultra Fine White rods Synthetic Alumina = 3 Micron = 6894.070

Yes The brown rods are actually quite refined and no where near coarse.

Atoma Diamond plate.

Atoma 140 = 100 Microns
Atoma 400 = 45 Microns
Atoma 600 = 29 Microns
Atoma 1200 = 15 Microns

This is where Atoma ends.

To go more refined with diamonds using a 14 to 16 micron increment like Atoma does then the next thing I am looking at is clearly in the 1 to 3 Micron range which should take care of any carbide sharpening.

This can be fulfilled by a EFF stone by DMT coming in at 3 microns and or strops and paddles with either diamond paste or diamond spray

Micron sizes obtained from https://docs.google.com/spreadsheets/d/ ... o/htmlview

Conversions calculated here: https://www.bestsharpeningstones.com/ar ... Calculator

[Pelagic]

I wouldn't get too concerned with carbide tearout. There's more important reasons to use diamond and CBN based abrasives IMO.

[Doeswhateveraspidercan]

I wouldn't get too concerned with carbide tearout. There's more important reasons to use diamond and CBN based abrasives IMO.

This is more of an exercise in comprehension for me to better comprehend all aspects involved in the whys of sharpening and what aspects are involved than to prove a definitive black and white conclusion which is impossible with all the factors involved for one with such an limited intellect as my own.

This thread and the low grit sharpening thread and the serrations compendium have been really wonderful.

With the arrival of my final two Atoma plates I am pretty sure the purchases are done with the exception of perhaps some Diamond spray as I already have strops and Diamond paste. Not sure at the moment what they are it has been some time since I used them.

Something I am very interested in is going from the 140 Atoma to the 400 and 600 and then 1200 and then using some of the lower micron paste I already own to see if there is much of a difference especially with S30V and S90V.

For example I love the finish of the brown rods on steels like 440C, Cruewear, M4, VG10 being that they are high Chromium oxide carbides in these steels, or low as in the case of m4. The alumina rods which are harder then Chromium work fantastic on these where harder carbides like Vanadium are not present or not present in a higher percentage as Vanadium is equal in hardness to the Alumina used in Spyderco rods, or maybe even harder?

This is where the Atoma 1200 will come in as it is equal in Micron size to the brown rods but is diamond which is harder than any of the carbides.

After that move to lower Micron diamond paste and strops just to get optimum sharpening of the carbides I mean why not? almost there anyway right? Then maintaining using the strops should be doable.

I can see where Sal was going with the grit progression of the sharpmaker much better now than ever before.

The brown rods create a truly wonderful finish and the white going to 6 microns makes allot of sense but vanadium is just as hard as the medium being used to cut them and this is where I finally came to comprehend it is not just the heat treatment and Rockwell hardness of the steel alone we are dealing with at all but the very thing that makes these steels what they are and that is the carbides.

It explains allot about how well the sharp-maker works much easier with different steels like VG10 whose carbides are almost all Chromium which is softer than Alumina of the sharp-maker stones and rods. unfortunately ceramic also tends to load up with steel swiftly and require frequent cleaning.

I think allot of people are not understanding it is not just the HRC of the steel they are working with as clearly no steel alone can match the hardness of the carbides especially Vanadium. Clearly no Steel at a high heat treatment can match the hardness of Alumina or Chromium Oxide abrasives so that leaves us with the unmistakable conclusion that yes it is very much about the carbides as well or ignore them and go for coarse finished edges where it matters much less.

One thing I am certain of is that it is not all black and white but I would rather sharpen something with a bunch of Vanadium in it using diamond or CBN any day of the week.

Heck the way the Diamond Atoma chewed into S90V on that Spyderco Military versus the Venev diamond stones in resin or the Wicked edge pro 100 grit stones was all it took to make it clear there are diamond stones and then there are diamond stones! Also explains why Strops of Chromium Oxide are not so great as well. Where as my diamond paste strops did so much better.

Clearly both items give up material when rubbed together so it is not just a matter of hardness but I think efficiency before boredom and sloppiness creep into the sharpening process.

Given a choice I would rather make 40 strokes per side than 400 to achieve the same result or perhaps a fatigue factored lesser result.

Yes a softer substance can cut a harder substance but I do not believe this applies I think what is happening is the carbides must be resisting sharpening efforts until the just pull away with the steel being sharpened as clearly Alumina can not cut Vanadium wear against it OK, Stress fracture it OK pull it out with the steel it is embedded in ok but if your were to take a brick of Alumina and a brick of Vanadium and rub them together I am sure it without impact you would have a bit of a stale mate going on. Similarly take that same brick of Chromium Oxide and Vanadium repeat the process and the Chromium Oxide is going to make a nice green Slurry.

Next is to start using the new stones then will have something more real world to discuss, thanks for this forum and a sounding board to bounce these ideas off of and learn from the members.

When it comes to sharpness however I am certain geometry and thinness behind the edge are the most critical factors but hey why not cover all bases?

Even a knife with perfect geometry and thinness behind the edge can be improved by working with all aspect of sharpening and that includes the carbides and the ease of sharpening by choosing the correct abrasives for the carbides more than the steel.

Although without the rest of the components that make up steel it is silly to discuss perhaps I should say pick the abrasive for the hardest component of the steel which is the carbide. :)

[Pelagic]

You're definitely onto something with the fatigued apex. Diamond, CBN, and even some SiC and ceramic products that cut aggressively will yield a better apex. You want the abrasive to win the war against your blade 100%. If your blade is putting up a fight, you're fatiguing the steel. Think of it like this. Take an extremely sharp and thin kitchen knife and cut a slice of pie, then do it with a butter knife. The knife is your abrasive, the slice of pie is the blade. The slice you cut with the sharp, thin knife will come to a perfect undisturbed point, while the slice you cut with a butter knife will be crushed. You can see this with tomatoes as well. If you're cutting something with utmost effectiveness, you're preserving the qualities of what you're cutting. There's probably a better way to explain it but oh well. A stone that cuts good simply removes steel and leaves the remaining steel untouched.

Also, I believe if you are stropping a high carbide steel with diamonds, you're probably completely negating any negative impact from using ceramic to refine the bevel and apex. If you go through your Atomas (and just so you know, the Atoma 1200 isn't equal to the brown rods, don't worry about grit rating, just observe the finish) and move onto ceramic, unless you're completely removing the previous scratch pattern, you're mainly just going to be taking off the high points of the scratches (hitting the mountains, leaving the valleys). Once you strop with diamonds any exposed carbides should be cut cleanly IMO. And if you ARE aiming to completely remove the scratch pattern, I'd assume you are eventually going for an extremely fine finish with more than one strop. Which I think should cut any exposed carbides effectively. Just my 2 cents. I use diamond powder on my strops and they cut insanely fast. I can skip the ceramic or any other high grit stones. I could easily stop at a 1200 grit plate and achieve a complete 0.1 micron finish in a matter of minutes. I like the higher concentration because I believe that stropping inherently fatigues the apex to an extent, but this phenomenon is reduced when extremely light pressure is used and the strop is cutting aggressively.

[Cambertree]

Doeswhatever, the alumina abrasive particles in the Sharpmaker rods are actually the same in all of them - around 15 micron IIRC. The binder media and surface finish also have an effect on how the grit abrades and the finish it leaves.

The white F and UF rods are the same, for example, the UF rods just have a smoother finish.

The scratch pattern of the rods also becomes finer with time and use.

The Alumina particles, as I understand, used on the rods are generally 15 -20 microns. The different grits for fine and medium are attained by firing processes, not micron size. The CBN and diamonds used are 400 mesh. The ultra fines are made by tumbling the fine grits.

sal

Also there’s different types of carbides and interactions between alloy components within certain carbides. It’s not as simple as straight up Chromium, Tungsten, Molybdenum and Niobium carbides.

As far as I’m aware, the Mohs scale is not generally used for indicating specific carbide hardnesses, as it is just an ordinal scale based on what material can scratch another material.

Larrin wrote an excellent article on carbide formation in knife steels:

https://knifesteelnerds.com/2019/07/15/ ... fe-steels/

It’s great to see you heading down the rabbit hole, brother. :)

And yes, I agree: geometry and thinness behind the edge are key (along with a few other factors).

You referred to Murray Carter earlier. He’s a good teacher. A lot of his material is on Youtube.

Also The Razor Edge Book of Sharpening by John Juranitch basically covers the same fundamentals. I think I might have recommended it to you before.

The King stones which Murray sells tend to be optimised for sharpening simple carbon steels rather than higher carbide PM steels, but they’re good stones to have in your kit to practice with. Bear in mind, they need to be flattened regularly - they are designed to be on the softer side to continually release fresh alumina abrasive.

[Doeswhateveraspidercan]

You're definitely onto something with the fatigued apex. Diamond, CBN, and even some SiC and ceramic products that cut aggressively will yield a better apex. You want the abrasive to win the war against your blade 100%. If your blade is putting up a fight, you're fatiguing the steel. Think of it like this. Take an extremely sharp and thin kitchen knife and cut a slice of pie, then do it with a butter knife. The knife is your abrasive, the slice of pie is the blade. The slice you cut with the sharp, thin knife will come to a perfect undisturbed point, while the slice you cut with a butter knife will be crushed. You can see this with tomatoes as well. If you're cutting something with utmost effectiveness, you're preserving the qualities of what you're cutting. There's probably a better way to explain it but oh well. A stone that cuts good simply removes steel and leaves the remaining steel untouched.

Also, I believe if you are stropping a high carbide steel with diamonds, you're probably completely negating any negative impact from using ceramic to refine the bevel and apex. If you go through your Atomas (and just so you know, the Atoma 1200 isn't equal to the brown rods, don't worry about grit rating, just observe the finish) and move onto ceramic, unless you're completely removing the previous scratch pattern, you're mainly just going to be taking off the high points of the scratches (hitting the mountains, leaving the valleys). Once you strop with diamonds any exposed carbides should be cut cleanly IMO. And if you ARE aiming to completely remove the scratch pattern, I'd assume you are eventually going for an extremely fine finish with more than one strop. Which I think should cut any exposed carbides effectively. Just my 2 cents. I use diamond powder on my strops and they cut insanely fast. I can skip the ceramic or any other high grit stones. I could easily stop at a 1200 grit plate and achieve a complete 0.1 micron finish in a matter of minutes. I like the higher concentration because I believe that stropping inherently fatigues the apex to an extent, but this phenomenon is reduced when extremely light pressure is used and the strop is cutting aggressively.

Thank you.

Diamond powder? please tell me where to obtain your set up and what micron the diamond powder is at I have heard of Diamond Paste, Diamond Films and diamond Spray but not powder. How is applied etc...

I would like to copy what you have shared.

[Pelagic]

I usually add the powder to compounds but occasionally use it dry. It can work with spray as well, but I quit using spray a while back since the powder is so cheap and cuts so quickly. Look for the $8 vials on ebay that are slightly thicker than a pencil and about 2 inches tall. They ship from Boca Raton. The 0.1 micron powder will have you whittling hairs both ways with ease, and 3 micron will HOG OFF material for a strop. Super fast burr elimination. You just have to keep the pressure light and check the blade after 1-3 passes or else you'll be looking at a polished bevel quickly (unless that's what you're going for). But it obviously depends on how much you add.

[Doeswhateveraspidercan]

Thank you very much Pelagic for the swift reply helped me during a recent purchase.

[Pelagic]

Thank you very much Pelagic for the swift reply helped me during a recent purchase.

No problem, try it out.