Stones recommendations for high HRC, and vanadium carbide steels.

[Andrei]

I hope my post will help the topicstarter.
Due to my occupation, I have to sharpen various steels, including modern monsters among steels, such as Rex121 and K390. In this case, I use a fairly simple set of stones.
An excellent fast working stone from a local Russian manufacturer (I don't know if I can give a link to the site) at 600grit, then Shapton Pro 1000, 2000, 5000, followed by a natural stone of 10000grit. Of course, natural stone almost does not work with high-alloy steels, but nevertheless, the nature of the knife cut after it changes noticeably for the better.
Perhaps my method works because I am sharpening a thin cutting edge, typically about 0.1mm thick, due to the small contact between the steel and the grindstone.
I also recommend going to the official website of Venev diamonds, there stones in the size 200/83/10 cost $ 50- $ 65 and the grain size is indicated in microns, which avoids confusion with the grain size by different standards. I also have two small Venev diamond stones, about which I can only say good things, but I do not use them when sharpening "monsters" as diamonds work much harder than ordinary stones.

 

[Andrei]

3

 

[KingShapton]

There have already been many good recommendations, here are a few tips from me. Admittedly, they are therotic, unfortunately I haven't had a HAP40 knife to sharpen (another item on my long-term wish list).

First a link to the website of fine-tools.com, there you will find a table on which you can find Shapton's recommendations for Shapton Pro's (Kuromaku) the right grit size for a certain steel. I don't know if the same recommendation applies to the Glass Stones, but they were made for high HRC numbers.

https://www.fine-tools.com/shapton-instructions.html
According to the table, for HSS (which includes HAP40) these would be # 220, # 1000 and # 12.000. Whether it makes sense to finish on # 12,000 is another issue, but the jump may give you a toothy edge that is also refined.

As others have written before me, Sigma Select II Stones will definitely work, the same goes for diamond / CBN.

In "the other forum" you can find more stones that work with HAP40 using the search function. To my great surprise you can find several posts there that the King 1200 also works well with HAP40. Again, there are experiences from third parties, I don't know whether it works.

However, I would be very happy about the King 1200 if it were true, it is one of my favorites among the synthetic stones anyway.

I hope this helps a little with the decision ?!

And before I completely forget, Merry Christmas to everyone reading this today.

 

[Blank Blades.]

I wanted to update. So I ordered a venev Phoenix 8×3 240/400. The 400/800 was out of stock. It was probably a good thing I think stopping at around 700 grit JIS is probably a good place for those super steels 10v, s30v, rex121 (if I happen to run into it). I'm actually wondering to myself if my jnats would work on them since if I recall correctly the abrasive is silicon

 

[KingShapton]

I wanted to update. So I ordered a venev Phoenix 8×3 240/400. The 400/800 was out of stock. It was probably a good thing I think stopping at around 700 grit JIS is probably a good place for those super steels 10v, s30v, rex121 (if I happen to run into it). I'm actually wondering to myself if my jnats would work on them since if I recall correctly the abrasive is silicon

Let us know how happy you are with it.

 

[inferno]

I wanted to update. So I ordered a venev Phoenix 8×3 240/400. The 400/800 was out of stock. It was probably a good thing I think stopping at around 700 grit JIS is probably a good place for those super steels 10v, s30v, rex121 (if I happen to run into it). I'm actually wondering to myself if my jnats would work on them since if I recall correctly the abrasive is silicon

these will probably be slower than regular stones. there is no real need imo for diamonds below 1k. the stones are so coarse so they just scoop out everything anyway.

jnats might be silicon. but not silicon carbide (nor nitride).

 

[Blank Blades.]

Let us know how happy you are with it.

Sure thing. I will try them on my knives right when I get them to see how they work with more traditional steel. Of course I will wait until I have to sharpen a customers super steels before I decide what my opinion will be.

these will probably be slower than regular stones. there is no real need imo for diamonds below 1k. the stones are so coarse so they just scoop out everything anyway.

jnats might be silicon. but not silicon carbide (nor nitride).

Idk I kind of believe the people saying you need diamonds or cbn for some of the vanadium carbide steels. Those things aren't like blue super, or sg2 and the like.

Good point about the silicone in jnats.

 

[kayman67]

I'd say under 1000 makes much more sense to have diamond or cbn plates in different binders, than above, if I would ever need to take one over the other.

 

[inferno]

Idk I kind of believe the people saying you need diamonds or cbn for some of the vanadium carbide steels. Those things aren't like blue super, or sg2 and the like.

you will soon find out.

i have not had any problems with s30v (high hardness), r2, srs15 and real hss stuff with shapton pro1k and below. but as you get up to maybe 3-4k then you will notice that regular stones become slower with these steels compared to carbons and low alloyed ss like aeb-l/12c27/vg10 etc.

i think its because the actual abrasive particles are so big in these stones compared to the carbides in the steel.
shapton 500 is 30micron particle size, 1k is 15micron. 4k is 3 micron. the carbides in these supersteels are 1-5 microns. the carbides reside at grain boundaries. with the coarse stones i get the feeling you can plow out several carbides deep/wide trenches in the steel.

now the abrasives are usually not shaped like buckets of excavators and not all of them are sticking up of course. but if the abrasive size would have no meaning/effect at all then it would be impossible to sharpen any high carbide/hard carbide steels with regular stones. but it isn't.

 

[M1k3]

these will probably be slower than regular stones. there is no real need imo for diamonds below 1k. the stones are so coarse so they just scoop out everything anyway.

jnats might be silicon. but not silicon carbide (nor nitride).

Depends. Resin bonded diamond aren't the fastest or slowest. They are consistent cutters though. Roughly the same cutting speed on simple carbon steel as on high alloy steels. And everything in between.

 

[M1k3]

And low grit diamond will give a more consistent edge versus low grit non-diamond stones.

 

[KingShapton]

Depends. Resin bonded diamond aren't the fastest or slowest. They are consistent cutters though. Roughly the same cutting speed on simple carbon steel as on high alloy steels. And everything in between.

and you don't have to flatten them, so you save time.

 

[inferno]

but they will clog though.

 

[M1k3]

but they will clog though.

Eventually. Easy to deal with. Not any harder to fix than a dishing stone.

 

[inferno]

i just did a little test here. i took my srs-15 blade and ran it on the 220 pro. then jumped from the 220 to the 12k shapton pro.
and to my surprise it only took about 3-4 minutes to erase those scratches and put on the 12k finish. the 12k finish is not a real mirror.

and yes while srs15 is not 10% vanadium its still 1,5% C. Mo 2,75%, W 1,25%, V 1,5%, so we have 5,5% carbide formers in there ontop of the 13% Cr.
what didn't take 4 minutes was trying to get 1 single sharp shot of the edge after the 12k. at 1:1 mag. handheld. no flash. only got one side of the image sharp.

so is diamonds really needed? i'd say no.

 

[HumbleHomeCook]

I'm kinda imterested as to whether SiC sandpaper would do the trick on the super high alloyed steels.

SiC or AlO2 stones or paper will work on high vanadium steels but only up to a point. I think it might have already been stated so forgive me if I'm repeating another poster, but when you hit 4%+ vanadium carbide content, things change. The carbides are small enough that at low grits you're removing enough of them with the matrix that it doesn't matter too much. When start getting past 400-600 ANSI grit, you experience increasing diminishing returns. The abrasive size starts to align with the carbide size and those ceramics are softer than the carbides so at best they will be abrading them.

 

[dafox]

i just did a little test here. i took my srs-15 blade and ran it on the 220 pro. then jumped from the 220 to the 12k shapton pro.
and to my surprise it only took about 3-4 minutes to erase those scratches and put on the 12k finish. the 12k finish is not a real mirror.

and yes while srs15 is not 10% vanadium its still 1,5% C. Mo 2,75%, W 1,25%, V 1,5%, so we have 5,5% carbide formers in there ontop of the 13% Cr.
what didn't take 4 minutes was trying to get 1 single sharp shot of the edge after the 12k. at 1:1 mag. handheld. no flash. only got one side of the image sharp.

so is diamonds really needed? i'd say no.

View attachment 107536

View attachment 107537
View attachment 107538

Which srs15 knife, I own a couple Akifusas now.

 

[HumbleHomeCook]

i just did a little test here. i took my srs-15 blade and ran it on the 220 pro. then jumped from the 220 to the 12k shapton pro.
and to my surprise it only took about 3-4 minutes to erase those scratches and put on the 12k finish. the 12k finish is not a real mirror.

and yes while srs15 is not 10% vanadium its still 1,5% C. Mo 2,75%, W 1,25%, V 1,5%, so we have 5,5% carbide formers in there ontop of the 13% Cr.
what didn't take 4 minutes was trying to get 1 single sharp shot of the edge after the 12k. at 1:1 mag. handheld. no flash. only got one side of the image sharp.

so is diamonds really needed? i'd say no.

View attachment 107536

View attachment 107537
View attachment 107538

I think HT starts becoming a big factor here as if I recall it affects the carbide formation. I think I remember that chrome will form preferentially over vanadium. It would be interesting to know the elemental-carbide composition of the steel.

 

[M1k3]

i just did a little test here. i took my srs-15 blade and ran it on the 220 pro. then jumped from the 220 to the 12k shapton pro.
and to my surprise it only took about 3-4 minutes to erase those scratches and put on the 12k finish. the 12k finish is not a real mirror.

and yes while srs15 is not 10% vanadium its still 1,5% C. Mo 2,75%, W 1,25%, V 1,5%, so we have 5,5% carbide formers in there ontop of the 13% Cr.
what didn't take 4 minutes was trying to get 1 single sharp shot of the edge after the 12k. at 1:1 mag. handheld. no flash. only got one side of the image sharp.

so is diamonds really needed? i'd say no.

View attachment 107536

View attachment 107537
View attachment 107538

For SRS-15, R2/SG2, etc. diamonds aren't necessary at all. Move up to S90V and up level, yes, definitely preferred.

OP wants to sharpen ALL steels. Not just know if diamonds are necessary for 2-3% vanadium steels.

 

[inferno]

Which srs15 knife, I own a couple Akifusas now.

a beater akifusa

 

[inferno]

I think HT starts becoming a big factor here as if I recall it affects the carbide formation. I think I remember that chrome will form preferentially over vanadium. It would be interesting to know the elemental-carbide composition of the steel.

some of the carbide formers are stronger than others. the carbides they form can be softer or harder. and then you have multimetal carbides. like cr-carbides get doped with v to form harder cr carbides. W and V are the usual ones put in there for abrasion resistance.

 

[Deadboxhero]

some of the carbide formers are stronger than others. the carbides they form can be softer or harder. and then you have multimetal carbides. like cr-carbides get doped with v to form harder cr carbides. W and V are the usual ones put in there for abrasion resistance.

SRS -15 is mostly Chromium Carbide (M7C3)

Srs 15 has little vanadium and good amount of Chromium.

The ratio of C,Cr and V in that steel means it makes little Vanadium Carbide (MC) will form especially since the Vanadium element also has an affinity for forming with the chromium carbide.

Tungsten is not a strong enough carbide former to make its own carbides in the presence of stronger carbide formers.

It has to do with the atomic structure of W

It's outer election shell is too full especially it's sub D shell to want to make bonds with carbon and being a larger atom it has almost no zero mobility in the ocean of smaller iron atoms. So tungsten is not a strong enough of a forming element to make carbides of its own in the presence of that much Chromium.

Molybdenum is also weak at forming its own Carbides. Which is why there are no Molybdenum Monocarbides in steels like CPM 154 but rather it enriches and boosts the Chromium Carbide volume.

So they will both join with the Chromium and Vanadium Carbide upon cooling from liquid and or just be dissolved elements in the iron matrix during and after austenitizing. Dissolved tungsten will not have any appreciable effects compared to a steel that does not have dissolved tungsten either.

So the chromium carbide chemistry in a steel like SRS 15 will be Cr Mo V W Fe rich making up the "M"
For "Metallic Elements" in "M"7C3

A steel like SRS 15 will not really give problems on ceramic stones like a steel with more MC type Carbides.

I have a akifusa migaki 240mm in SRS15 that the manufacturer says is at 64rc that I have used on Choseras no problems.

The harder vanadium rich Chromium Carbides (M7C3) are still under 2000hv within the ranges of Alumina (Ceramic) abrasive hardness, Vanadium Carbide (MC) is 2800-3000HV so it gives softer alumina abrasive problems if the steel is heat treated to a harder matrix (60rc plus)and has significant volume of these particles.(+4% Vol.)

Here is a chart I made.

 

[Deadboxhero]

Nemo's earlier question about what steels are being discussed here is on point.

I've sharpened M390 to an excellent edge on JNats. HAP40 seemed to sharpen on Shapton Glass just fine. S110V and Maxamet are a different story. Diamonds all the way (I'm sure CBN is fine too), and stop at a coarse grit for a nice toothy long lasting edge. You can polish M390, but it seems like a silly thing to even try with S110V. But if you are cutting cardboard boxes all day, as I have been doing lately, having just moved, a nice coarse S110V edge is just the thing.

I assume that no one is insane enough to make an S110V kitchen knife. But if someone did, I'd at least take a hard look at it. Tomatoes would quiver in fear.

I have some S110v that I think would be rad for a 240mm sujuhiki.

Currently been playing with CPM 15v at 66.4rc and Rex 121 at 71rc.

Love the edge aggression and how ferociously it cuts.

 

[inferno]

i tried the 220 shapton on a s30v microtech. then the 12k again. the 12k cuts it. s30v clogs up the stone faster than srs15 though.
is the shapton 12k the honey badger of stones? i kinda doubt it but it cuts s30v at least. s30v is the highest alloyed steel i have around here.
so i can't test it on 10%V steels.

 

[kayman67]

This is highly misleading. In no test the sweet spot of 3-4% was problematic as far as "regular" stone cutting goes, but the edge retention started to be heavily in favor of diamonds or cbn abrasives. In a direct translation, you get way less than the best possible performance once you keep using the same stones, even if those can still form an edge.
Going higher %V is a different story altogether.

 

[HumbleHomeCook]

SRS -15 is mostly Chromium Carbide (M7C3)

Srs 15 has little vanadium and good amount of Chromium.

The ratio of C,Cr and V in that steel means it makes little Vanadium Carbide (MC) will form especially since the Vanadium element also has an affinity for forming with the chromium carbide.

Tungsten is not a strong enough carbide former to make its own carbides in the presence of stronger carbide formers.

It has to do with the atomic structure of W

It's outer election shell is too full especially it's sub D shell to want to make bonds with carbon and being a larger atom it has almost no zero mobility in the ocean of smaller iron atoms. So tungsten is not a strong enough of a forming element to make carbides of its own in the presence of that much Chromium.

Molybdenum is also weak at forming its own Carbides. Which is why there are no Molybdenum Monocarbides in steels like CPM 154 but rather it enriches and boosts the Chromium Carbide volume.

So they will both join with the Chromium and Vanadium Carbide upon cooling from liquid and or just be dissolved elements in the iron matrix during and after austenitizing. Dissolved tungsten will not have any appreciable effects compared to a steel that does not have dissolved tungsten either.

So the chromium carbide chemistry in a steel like SRS 15 will be Cr Mo V W Fe rich making up the "M"
For "Metallic Elements" in "M"7C3

A steel like SRS 15 will not really give problems on ceramic stones like a steel with more MC type Carbides.

I have a akifusa migaki 240mm in SRS15 that the manufacturer says is at 64rc that I have used on Choseras no problems.

The harder vanadium rich Chromium Carbides (M7C3) are still under 2000hv within the ranges of Alumina (Ceramic) abrasive hardness, Vanadium Carbide (MC) is 2800-3000HV so it gives softer alumina abrasive problems if the steel is heat treated to a harder matrix (60rc plus)and has significant volume of these particles.(+4% Vol.)

Here is a chart I made.

Excellent as always Shawn. I work in metallurgy every day and it's almost a dark art.

 

[inferno]

is there any documented tests/videos online where someone has tested
edge retention with diamonds vs regular stones on supersteels?

maybe at the same grit or with a similar resulting scratch pattern, since the type of binder will make stones behave finer/coarser than they are labelled. plated stones are always much coarser than regular stones for example.

preferably at realistic kitchen knife grits, above 2-3k jis.

i'm guessing there will be people who have tested and documented this considering how many guided sharpening systems there are.

 

[Blank Blades.]

is there any documented tests/videos online where someone has tested
edge retention with diamonds vs regular stones on supersteels?

maybe at the same grit or with a similar resulting scratch pattern, since the type of binder will make stones behave finer/coarser than they are labelled. plated stones are always much coarser than regular stones for example.

preferably at realistic kitchen knife grits, above 2-3k jis.

i'm guessing there will be people who have tested and documented this considering how many guided sharpening systems there are.

Idk about specifically diamonds, but cedric and ada gear and outdoors on YouTube tested how different angles and finishes effect different steels edge retention.

 

[KingShapton]

There are countless studies on this. From users in forums in different countries, from scientific research and so on.

The problem is always the same, you cannot perform a standardized test and compare the results objectively. There are so many influences that the test results will always be subjective.

To name a few influences that influence the result ... The surface when cutting, the cut material used (there are no standardized vegetables, 2 tomatoes behave differently), the knife used (outdoor or kitchen knife), the thickness of the blade , the steel used, which grind, how much force was exerted when cutting, which cutting technique was used, how accurately the knife was sharpened, was a guided system used (with or without pressure relief) or freehand sharpened, how clean was the deburring and so on. ..

The results will vary on each, which does well on paper cutting tests will fail on raw and fatty meat, or on a whole celery ...

I have read a lot of such tests and also followed a lot of discussions in various forums and have come to the conclusion that the results vary too much to deal with the tests of others or with the related discussions.

As with so many things in life, everyone has to make their own experiences and find out what works for themselves. Everything else is a waste of time from a certain level! I prefer to try things out myself than to have endless theoretical discussions. At some point it is more about someone who wants to be right in the discussion and no longer about the actual topic.

 

[KingShapton]

I have to add that I generally don't like to "over-theoretical" things. I like my own practical experience and that's part of the fun of this hobby.