High vanadium knives don't need diamond stones...

[000Robert]

425M is essentially similar to 420HC in its makeup, with no significant hard carbide content at all. Not enough extra carbon in the steel to form hard carbides with other elements in it, like chromium. And just a tiny bit of vanadium (0.1%) for grain refinement. I have an older 4-dot Buck 112 in 425M, and it's essentially indistinguishable from Buck's 420HC in terms of how it sharpens up. I sharpen it on a Norton Fine India (aluminum oxide) most of the time, with occasional touchups on a medium Spyderco ceramic. Either stone type handles it easily and both leave a great finish on the edge, which is why I use those in particular. They're my favorites for that knife and for most of my others in 420HC and similar steels.

Sometimes, natural stones can be kind of marginal with stainless steels like these. But other synthetic stones of most any type should handle them without issue.

Maybe they made the steel in my knife too hard. How hard is your 425M? I don't know exactly how hard mine is because the 65Rc file is the hardest that I have in my set.

 

[DeadboxHero]

Yeah if I remember correctly the issue with that section is that it's not talking about what kind of differentiated carbides so it's kind of useless for this context. It may be a certain percentage carbide, but of that percentage, how much of it is what kind of specific carbide? It didn't say. I'm saying this off the top of my head, though, so perhaps I merely missed such information when reviewing the mentions.

They are just keeping that chart simple and easy to digest.

M6C is what they are using for both "molybdenum carbides" and "tungsten carbides" which is significantly softer than the WC tungsten monocarbide we all think of for "tungsten carbides" which is closer in hardness to vanadium carbides depending on its chemistry.

M6C is also softer than harder M7C3 "chromium carbides" which is omitted from that chart perhaps for simplicity, so they just have the softer M23C6 for "chromium carbides" rather than both M7C3 and M23C6.

M = Metallic Element so M6C can be Mo rich, W rich etc.


Table from Verhoeven 2005 "Metallurgy for Bladesmiths" pg. 154

(Carbides aren't measured in HRC, they were converted for simplicity)

 

[Obsessed with Edges]

Maybe they made the steel in my knife too hard. How hard is your 425M? I don't know exactly how hard mine is because the 65Rc file is the hardest that I have in my set.

I have no definitive way of knowing how hard the 425M is in my 112. But seeing how it compares so similarly to Buck's current production 420HC (HRC 57-59), I'd have to assume it's probably in a similar hardness and wear-resistance ballpark. Steels of this type generally don't harden very well at much higher than that anyway, due to the limited carbon content at around 0.5%, give or take.

Other simple steels at HRC 60 or a little better, like 1095, can still sharpen up nicely on Arkansas stones. I have an older USA Schrade 8OT in that ballpark. The ease of sharpening is again due to the complete lack of hard carbides in such steel, and less about the heat-treated hardness of the matrix steel itself.

I'm wondering about the older 301. Buck contracted their older-generation 300-series knives to Camillus for manufacture, before Buck later started making them in-house (using 420HC currently). The Camillus-made knives were in 440A instead of 425M. 440A is a little higher in carbon content (0.6-0.75% or so) and also has more chromium at 16-18% or so, which adds a little bit of wear resistance as well as corrosion resistance. That might be enough to make it difficult on the Arkansas stones - but it would still be handled easily on any other synthetic stone (AlOx, SiC, diamond, etc.). I have an older Camillus-made Buck 307 in 440A, BTW.

 

[eKretz]

Yeah if I remember correctly the issue with that section is that it's not talking about what kind of differentiated carbides so it's kind of useless for this context. It may be a certain percentage carbide, but of that percentage, how much of it is what kind of specific carbide? It didn't say. I'm saying this off the top of my head, though, so perhaps I merely missed such information when reviewing the mentions.

It only mentions the specific percentage for M2 and M4 - saying that both have approximately 6 percent tungsten carbide composition. The difference in performance between the two owing rather to the higher Vanadium carbide percentage in M4.

 

[FortyTwoBlades]

I have no definitive way of knowing how hard the 425M is in my 112. But seeing how it compares so similarly to Buck's current production 420HC (HRC 57-59), I'd have to assume it's probably in a similar hardness and wear-resistance ballpark. Steels of this type generally don't harden very well at much higher than that anyway, due to the limited carbon content at around 0.5%, give or take.

Other simple steels at HRC 60 or a little better, like 1095, can still sharpen up nicely on Arkansas stones. I have an older USA Schrade 8OT in that ballpark. The ease of sharpening is again due to the complete lack of hard carbides in such steel, and less about the heat-treated hardness of the matrix steel itself.

I'm wondering about the older 301. Buck contracted their older-generation 300-series knives to Camillus for manufacture, before Buck later started making them in-house (using 420HC currently). The Camillus-made knives were in 440A instead of 425M. 440A is a little higher in carbon content (0.6-0.75% or so) and also has more chromium at 16-18% or so, which adds a little bit of wear resistance as well as corrosion resistance. That might be enough to make it difficult on the Arkansas stones - but it would still be handled easily on any other synthetic stone (AlOx, SiC, diamond, etc.). I have an older Camillus-made Buck 307 in 440A, BTW.

Chromium carbides alone are enough to be too much for Arkansas stones to handle appropriately. It's part of the reason why the old 440C Buck knives were notoriously difficult to sharpen back when they came out, as they were heat treated on the hard side and natural stones were still in much more common usage. Those old blades sharpen fine on synthetic abrasives, if slower than softer steels do, but will glaze an Arkansas.

 

[MolokaiRider]

Back before I knew any better I ran a CS American Lawman in CTS-XHP through my KME going through a full set of brand new Arkansas stones.

That was a major mistake. Ruined the stones and while chasing sharpness prematurely wore the edge down.

Luckily I lost that knife while hunting, so I would not have to be reminded of my idiocy.

 

[000Robert]

Chromium carbides alone are enough to be too much for Arkansas stones to handle appropriately. It's part of the reason why the old 440C Buck knives were notoriously difficult to sharpen back when they came out, as they were heat treated on the hard side and natural stones were still in much more common usage. Those old blades sharpen fine on synthetic abrasives, if slower than softer steels do, but will glaze an Arkansas.

I'm really not sure that they are Arkansas stones since I bought them 25 or so years ago. They are oilstones in my Hall's Pro Edge Wet Hone. I couldn't even find a photo of them on the internet. They are 2 3/8" X 11 1/8". There's a course, medium, and fine stone in a plastic case that holds oil in the bottom half.

 

[FortyTwoBlades]

I'm really not sure that they are Arkansas stones since I bought them 25 or so years ago. They are oilstones in my Hall's Pro Edge Wet Hone. I couldn't even find a photo of them on the internet. They are 2 3/8" X 11 1/8". There's a course, medium, and fine stone in a plastic case that holds oil in the bottom half.

View attachment 1821324View attachment 1821325

Those are synthetics. Look to be aluminum oxide stones.

 

[DeadboxHero]

It only mentions the specific percentage for M2 and M4 - saying that both have approximately 6 percent tungsten carbide composition. The difference in performance between the two owing rather to the higher Vanadium carbide percentage in M4.

Yea, it does say "molybdenum carbides" and "tungsten carbides" for M2 but you also see they defined the hardness for those carbides as the same as each other which coincidentally is also the same hardness for the softer M6C. Looks like they were just trying to keep things simple.

So its 2% Vanadium rich MC and 11% Tungsten-Molybdenum rich M6C based on what they are saying. Also, the exact fraction can change with austenitizing temperature.

Meanwhile, CPM M4 has less M6C carbide but more Vanadium rich MC

Roberts 1998
M2
12% M6C, 2.2% MC
CPM M4
5% M6C, 5.5% MC



I believe they were just trying to oversimplify things which unfortunately leads to confusion about there being carbides that aren't inside the steel.

There are no sexy WC tungsten carbides in tool steels. Just the softer, tungsten rich M6C.

 

[000Robert]

Those are synthetics. Look to be aluminum oxide stones.

I'm not sure, but they won't even scratch my 425M.

 

[FortyTwoBlades]

I'm not sure, but they won't even scratch my 425M.

It's very possible that they're glazed or clogged. They should cut it just fine. 425M has a maximum hardness of 57-60 RC (one reference of a handful I was able to turn up quickly can be found here) which is not remarkably hard, and it doesn't have sufficient alloying elements beyond chromium to result in any harder carbides than chromium carbides forming. Aluminum oxide will readily cut chromium carbides without issue, and so there is either some troubleshooting that needs to be done to the stones, user technique, or both.

 

[000Robert]

It's very possible that they're glazed or clogged. They should cut it just fine. 425M has a maximum hardness of 57-60 RC (one reference of a handful I was able to turn up quickly can be found here) which is not remarkably hard, and it doesn't have sufficient alloying elements beyond chromium to result in any harder carbides than chromium carbides forming. Aluminum oxide will readily cut chromium carbides without issue, and so there is either some troubleshooting that needs to be done to the stones, user technique, or both.

Nope. I guess Buck messed up or something because my 65Rc file just skates across all three blades. They are harder than 65Rc. The year mark is, "X".

 

[Obsessed with Edges]

Chromium carbides alone are enough to be too much for Arkansas stones to handle appropriately. It's part of the reason why the old 440C Buck knives were notoriously difficult to sharpen back when they came out, as they were heat treated on the hard side and natural stones were still in much more common usage. Those old blades sharpen fine on synthetic abrasives, if slower than softer steels do, but will glaze an Arkansas.

I also have an older 2-dot 112 from Buck, in 440C. That particular knife is THE reason why I set my 'ease of sharpening threshold' at something less wear-resistant than 440C, when using Arkansas stones. Had no luck with them at all, on that blade, when I first tried it many years ago.

It's possible in my mind also, that some blades in 440A could be just troublesome enough as well, on Ark stones.

 

[Obsessed with Edges]

I'm really not sure that they are Arkansas stones since I bought them 25 or so years ago. They are oilstones in my Hall's Pro Edge Wet Hone. I couldn't even find a photo of them on the internet. They are 2 3/8" X 11 1/8". There's a course, medium, and fine stone in a plastic case that holds oil in the bottom half.

View attachment 1821324View attachment 1821325

The coarse and medium stones do look like synthetic stones. In most of the tri-hone sharpening sets from many vendors, that'll be common and even the norm. The coarse grey/black stone will either be in SiC or AlOx, and the orange-color medium stone is aluminum oxide. In these tri-hone sets, the fine stone is often an Arkansas stone and occasionally, the medium is as well. I have an older unbranded set, bought maybe 30 years ago, with a SiC coarse stone, a 'medium' Arkansas (Washita-type stone) and a translucent Arkansas stone for the 'fine'. And I recently bought a Smith's tri-hone set for cheap, which looks just like the set you've pictured, with a synthetic Coarse (probably SiC) and the orange medium in aluminum oxide, and a medium/soft Ark stone for the 'fine'.

I agree with FortyTwoBlades - something strange is going on. Either with the effectiveness ('defectiveness', maybe) of the stones themselves or something else. 425M steel simply doesn't have the makeup or capability, carbide-wise or hardenability-wise, to create issues like this, on even the least-hard of sharpening stones.

In recent years, I've occasionally seen some vendors making/selling stones (water stones) that were actually 'manmade' like a synthetic stone, but using graded grit from natural stones, bound like a synthetic. Those stones were marketed to users of woodworking tools like chisels & plane irons (usually in simple carbon steels), I think intended to release grit like water stones are designed to do. The thing I didn't like, in seeing ads for those, is that they look too much like synthetic stones and might mislead buyers as to their capabilities. I DOUBT that your set is among this unusual grouping of stones. But there's lots of room for vendors to put a lot of inferior or misleading product out there.

 

[FortyTwoBlades]

The coarse and medium stones do look like synthetic stones. In most of the tri-hone sharpening sets from many vendors, that'll be common and even the norm. The coarse grey/black stone will either be in SiC or AlOx, and the orange-color medium stone is aluminum oxide. In these tri-hone sets, the fine stone is often an Arkansas stone and occasionally, the medium is as well. I have an older unbranded set, bought maybe 30 years ago, with a SiC coarse stone, a 'medium' Arkansas (Washita-type stone) and a translucent Arkansas stone for the 'fine'. And I recently bought a Smith's tri-hone set for cheap, which looks just like the set you've pictured, with a synthetic Coarse (probably SiC) and the orange medium in aluminum oxide, and a medium/soft Ark stone for the 'fine'.

I agree with FortyTwoBlades - something strange is going on. Either with the effectiveness ('defectiveness', maybe) of the stones themselves or something else. 425M steel simply doesn't have the makeup or capability, carbide-wise or hardenability-wise, to create issues like this, on even the least-hard of sharpening stones.

In recent years, I've occasionally seen some vendors making/selling stones (water stones) that were actually 'manmade' like a synthetic stone, but using graded grit from natural stones, bound like a synthetic. Those stones were marketed to users of woodworking tools like chisels & plane irons (usually in simple carbon steels), I think intended to release grit like water stones are designed to do. The thing I didn't like, in seeing ads for those, is that they look too much like synthetic stones and might mislead buyers as to their capabilities. I DOUBT that your set is among this unusual grouping of stones. But there's lots of room for vendors to put a lot of inferior or misleading product out there.

The whole "synthetic natural" thing is new, but the stones could have a poor grit-to-binder ratio. The binders used in aluminum oxide and silicon carbide stones will still lightly abrade plain steel but are too soft for chromium carbides.

 

[eKretz]

Yea, it does say "molybdenum carbides" and "tungsten carbides" for M2 but you also see they defined the hardness for those carbides as the same as each other which coincidentally is also the same hardness for the softer M6C. Looks like they were just trying to keep things simple.

So its 2% Vanadium rich MC and 11% Tungsten-Molybdenum rich M6C based on what they are saying. Also, the exact fraction can change with austenitizing temperature.

Meanwhile, CPM M4 has less M6C carbide but more Vanadium rich MC

Roberts 1998
M2
12% M6C, 2.2% MC
CPM M4
5% M6C, 5.5% MC



I believe they were just trying to oversimplify things which unfortunately leads to confusion about there being carbides that aren't inside the steel.

There are no sexy WC tungsten carbides in tool steels. Just the softer, tungsten rich M6C.

From other things I've read, there are indeed MC (WC) carbides, just in much smaller percentages. And my original message was regarding T15, not M2 anyway; was just using that article as an example that tungsten carbides are present in certain steels.

 

[FortyTwoBlades]

Nope. I guess Buck messed up or something because my 65Rc file just skates across all three blades. They are harder than 65Rc. The year mark is, "X".

Files do blunt, so just because it's skating doesn't necessarily mean that the file is softer than the blade is. Furthermore, the greater the difference in hardness between the abrasive and the substrate the easier the one will remove material from the other, meaning that while diamond will abrade sintered aluminum oxide, it does so slower than it would, for instance, plain 1095 steel, and leaves shallower marks. 425M is compositionally a "halfway" between 440A and 420HC. Both only form chromium carbides as their most wear-resistant carbide and 420HC, which is capable of achieving the highest quenched hardness of the three, tops out at a quenched hardness of 62 RC. That being said, chromium carbides themselves are about 65/70 HRC and this is why there are special "stainless files" that are given a hard surface coating that allows them to more readily cut martensitic stainless steels that would otherwise wear heavily on the files.

 

[DeadboxHero]

From other things I've read, there are indeed MC (WC) carbides, just in much smaller percentages. And my original message was regarding T15, not M2 anyway; was just using that article as an example that tungsten carbides are present in certain steels.

WC is not compatible with the other MC carbides.

WC is HCP

The other MC carbides are FCC and interchange some metallic elements.

 

[000Robert]

Files do blunt, so just because it's skating doesn't necessarily mean that the file is softer than the blade is. Furthermore, the greater the difference in hardness between the abrasive and the substrate the easier the one will remove material from the other, meaning that while diamond will abrade sintered aluminum oxide, it does so slower than it would, for instance, plain 1095 steel, and leaves shallower marks. 425M is compositionally a "halfway" between 440A and 420HC. Both only form chromium carbides as their most wear-resistant carbide and 420HC, which is capable of achieving the highest quenched hardness of the three, tops out at a quenched hardness of 62 RC. That being said, chromium carbides themselves are about 65/70 HRC and this is why there are special "stainless files" that are given a hard surface coating that allows them to more readily cut martensitic stainless steels that would otherwise wear heavily on the files.

My files are brand new and they work great on every other knife that I have. Maybe the steel is not 425M? Buck may have made a mistake and made my blades from a different steel, I'm not sure. But my 301 is the reason that I bought my DMT decades ago. I guess I need to have the steel tested.

 

[FortyTwoBlades]

My files are brand new and they work great on every other knife that I have. Maybe the steel is not 425M? Buck may have made a mistake and made my blades from a different steel, I'm not sure. But my 301 is the reason that I bought my DMT decades ago. I guess I need to have the steel tested.

It is probably the stated 425M. Your approach towards sharpening them just needs alteration. Even their notoriously hard 440C will be easily cut by synthetic stones in good condition.

If you don't mind marring the blade surface, try using the chisel-like end corner of the file like a scribe to scratch the blade. Just because the file isn't biting isn't always a problem of hardness. Most people complain of the 425M blades not holding an edge well. It's not magic steel, and isn't even considered "good" by current standards. Stainless is just hard on files, especially martensitic hardened stainless. And that particular stone set sounds like there's something funky going on with it that would need refurbishing to work well.