Problems sharpening/using PM-V11 blades

[Steve Voigt]

I'm a little late here but I wanted to add a couple thoughts.

Mike, powdered metal blades theoretically should provide the finest edge.

Derek, what evidence is there that PM V11 provides the finest edge? I'm not agreeing or disagreeing; I'd just like to know if there is data, even if it's subjective observation. Veritas seems to have done excellent and thorough testing, but it was limited to ease of sharpening, impact resistance, and wear resistance. I have to say, if it does provide the finest edge, I'm pretty sure folks would be announcing that from the hilltops…

I realize this is a nearly-defunct thread, but...

The *entire* point of powdered metal steels is that they achieve finer grain structure (and in particular smaller carbide sizes) than would otherwise be possible for a conventionally processed steel of similar composition. Fineness of structure is the principle driver of "sharpness" as commonly defined by woodworkers, so Derek is spot-on in his reply: There should be no significant tradeoff in achievable sharpness from using a steel like PM-V11. In my experience it's comparable to low-alloy tool steels like O1, which achieves very fine structure even with conventional processing, and better than non-PM higher-alloy steels like A2 (though cryo treatment also refines grain structure and seems to close the gap in my experience). It may take different technique, sharpening media, and/or level of effort (as was the case here) to actually achieve that level of sharpness, though.

Patrick, I'm not sure what to make of the above quote. By "steel of similar composition," you presumably mean something like A2 or HSS, although it's hard to know, since I (we?) don't actually know the composition. Or do you mean O1 or 1095? Similarly, when you say "it's comparable [in achievable sharpness] to low-alloy steels like O1," do you mean it gets as sharp, or a little sharper, or not quite as sharp?

It might seem like I'm nitpicking, but I don't think so. To me, the most important question is what steel(s) get sharpest? Ease of sharpening is second, and edge retention is third. In the past, all the research into "wonder steels" was focused on the third category, I suppose in the rather futile hope that beginners could avoid sharpening forever. With PM V11, Veritas at least seems to be acknowledging the problem with these steels (like A2 or CPM whatever), that they fall short in the first two categories; from all accounts PM V11 gets sharper, and is easier to sharpen, than something like A2. But I don't really care. I want to know if something gets sharper than O1, 1095, or Japanese blue or white paper steels. If someone can show me that Pm V11, or anything else, actually takes the finest edge, I will run out and buy it tomorrow. But until then, I'll stick to the steels that are simplest and purest. My personal feeling, as Mike Cherry said above, is that there's no free lunch.

[Kees Heiden]

I am pretty sure that PMV-11 is a stainless steel. I actually tested that, trying to get the steel to rust. While O1 readilly turned brownish/blackish and A2 got some tarnishing too, PMV was unaffected. To make a steel stainless it needs a bunch of chrome, or a bunch of nickel, or both. At least 14% if I remember correctly. The chrome that isn't occupied with the chromium oxide layer on the outer skin of the steel will form chromium carbides. That stuff is hard, not as hard as vanadium carbides, but still harder then ferrum carbides (cementite if I remember correctly) and certainly harder then the tempered martensite structure that makes up most of the body of a well hardened steel.

Now I am going out on a limb. I suspect that the chromium carbides don't like to be abraded by our sharpening media, except diamonds. I think they prefer to be ripped out of the steel structure, leaving behind craters. I have seen a picture of a powdered metal on a knife forum (not PMV-11, another one) where the chromium carbides were still several micrometers large. A lot better then in good old fashioned D2, but still not quite as small as a good sharp edge is supposed to be.

All this probably doesn't make a difference when you stop sharpening on a 1000 grit waterstone...

[Patrick Chase]

All this probably doesn't make a difference when you stop sharpening on a 1000 grit waterstone...

I sharpen to a level that optimizes woodworking performance, and my comments were made in the context. Sorry I wasn't more clear.

In particular, I hone to <=1 micron abrasive size on both waterstones (Sigma 13K or Shapton Pro 15K) and diamond (0.5 micron paste or 0.5 micron 3M 661X/668X film). I don't notice a difference in keenness between my PM-V11 and O1 blades in practice, though I do notice some (negative) difference between those and non-cryo A2 blades (the A2 blade from my L-N #8 on the other hand takes a very nice edge indeed). I've also examined blades under 'scopes and didn't see multi-micron craters in the PM-V11. Note that the specifics of the sintering process come into play as well, so even if you looked at another "PM" steel with the same composition your observations wouldn't necessarily carry over to PM-V11.

I'm sure that a straight-razor fanatic would hone to a different level and draw different conclusions.

[Mike Henderson]

I finish on a Shapton 8000 stone and that's sharp enough for me. I mostly use my chisels for chopping so after a couple of hits, some finely prepared edge is gone.

If I can shave hair with my chisel, I figure it's sharp enough.

If I have to pare, I go back to my 8000 stone and make sure the chisel is in just-sharpened condition.

Mike

[Patrick Chase]

Harrumph!!

I would note that sometimes what is not said is far more significant than what is.

[Derek Cohen]

Derek, what evidence is there that PM V11 provides the finest edge? I'm not agreeing or disagreeing; I'd just like to know if there is data, even if it's subjective observation. Veritas seems to have done excellent and thorough testing, but it was limited to ease of sharpening, impact resistance, and wear resistance. I have to say, if it does provide the finest edge, I'm pretty sure folks would be announcing that from the hilltops…

It might seem like I'm nitpicking, but I don't think so. To me, the most important question is what steel(s) get sharpest? Ease of sharpening is second, and edge retention is third. In the past, all the research into "wonder steels" was focused on the third category, I suppose in the rather futile hope that beginners could avoid sharpening forever.

Hi Steve

The short answer is that, in my understanding - hence the "theoretical" addition to my comment - PM steel is capable, depending on the recipe, of having a finer grain structure than steels prepared in a less precise way. Added to this, I was informed that PM-V11 is one of those recipes that is aimed at a fine grain structure. I have no reason to not believe my source.

What I can state, which is factual and not theoretical, is that I have compared a number of steels in a real world manner, and the results backed up the claims for PM-V11. It is a steel that both gets very sharp, and also holds that edge extremely well. It far, far outclasses O1 and A2 in the latter area when it comes to chopping through end grain with a chisel (as expected in dovetailing), only just pipped by the Koyamaichi white steel chisel I used in a comparison.

I do not have any trouble getting steels - any type – sharp. Getting sharp just requires the appropriate honing medium for each particular steel you use (some media will obviously work a wider range than others; some a very narrow range). Not all media suit all steels. Getting sharp is important, but equally so is maintaining that edge. The woods I work are hard and abrasive (high silica content). As soon as the edge dulls, the tool’s performance drops off. For illustration, comparing the LN #51 shooting plane and the LV shooting plane, it was easily demonstrated that O1 steel dulled very rapidly. It matters far less whether it was capable of equaling or bettering PM-V11 in sharpness since it dulled so rapidly that it was essentially an obstacle to good work.

The “wonder steels” have an important and relevant role to play. Just perhaps not for everyone. And they are certainly not a “beginners” steel. For myself, this is serious steel, which hopefully helps me do serious work.

Regards from Perth

Derek

Links: http://www.inthewoodshop.com/ToolRev...tingPlane.html

http://www.inthewoodshop.com/ToolRev...sCompared.html

[Patrick Chase]

Hi Steve

The short answer is that, in my understanding - hence the "theoretical" addition to my comment - PM steel is capable, depending on the recipe, of having a finer grain structure than steels prepared in a less precise way. Added to this, I was informed that PM-V11 is one of those recipes that is aimed at a fine grain structure. I have no reason to not believe my source.

A more accurate way of stating that would be: "PM steel is capable, depending on the recipe, of having a finer grain structure than steels of similar composition prepared using conventional processing". Steels that are high in certain alloyants tend to form coarse grain structures and large carbides with conventional processing, and PM prevents that from happening. Also, it isn't a question of more or less precise.

That is not however to say that such a high-alloy PM steel would be expected to have a finer grain structure than a conventionally processed low-alloy steel like O1, which has inherently fine structure without resorting to PM. PM expands the range of compositions that you can use while still achieving a given level of "sharpness", but it isn't a silver bullet. In my experience PM-V11 is more than good enough for woodworking, though.

[Kees Heiden]

Funny thing about your chisel test Derek, is that the Japanese white steel and the PMV-11 scored almost the same. And they couldn't be more different. The White steel has almost no alloying elements, a little bit of silicone that's all. While PMV-11 contains almost 20% of stuff that isn't iron or carbon.

I suspect that in a chisel high hardness (resists deformation and increases wear resistance) and fine grain (increases toughness) are important aspects.

[Derek Cohen]

I suspect that in a chisel high hardness (resists deformation and increases wear resistance) and fine grain (increases toughness) are important aspects.

Hi Kees

What I found interesting in the tests I conducted on chopping vs paring with chisels was that they produced such different results. Where White Steel (Koyamaichi) left all for dust in the chopping, it did not perform this well in the paring test ...

"The A2 and O1 blades were almost as good as the WS, really only a little behind. I’d place the O1 fractionally ahead of the A2 in the first 25 strokes and at the end of the experiment. The extra durability of the A2 was not evident in this assessment.

Impact vs abrasion resistance differences?

This was done prior to the advent of PM-V11, and so this was not compared.

Regards from Perth

Derek

Links: http://www.inthewoodshop.com/ToolRev...g-5Steels.html

http://www.inthewoodshop.com/ToolRev...selParing.html

[Kees Heiden]

Yes, I think in a plane an iron dulls in a different way then in a chisel. And pairing with a chisel has more in common with a plane. The dulling effect during chopping is harder to grasp in a theoretical model.

White steel hasn't anything specific to reduce the abrassion. Apart from the high hardness like in many of those nice Japanese chisels. As far as I know the major abrassion resistance factors are hardness and chemical composition.

Toughness can be advanced with some alloys, with lower hardness, but also with a very fine grain of the steel.

[Pat Barry]

The grade stamp on the steel isn't always going to be a true indicator of how it will perform as there can be a significant difference in material composition, manufacturing process and treatment process variability and perceptible things such as finished hardness within any of the steel categories. In other words, one mans O1 isn't necessarily the same as another's because they didn't come from the same steel supplier / factory. I speculate that this is less the case with the PMV11 as it is most likely a single source supplier and because of that, many of the variables noted above are reduced or eliminated.

[Brian Holcombe]

I don't have the need for it, but I wonder how something like blue 2, worked by Konobu or Kikuhiromaru would perform in the paring test.

Derek, in practical use, how do you feel your Kiyohisa's perform in paring against these other steels.

[Derek Cohen]

Hi Brian

The Kiyohisas are in a class of their own. They are very easy to hone, and yet hold an edge for such a long time. Keep in mind, however, they are slicks and do not get used in a rough manner - fine paring only.

Regards from Perth

Derek

[george wilson]

Derek,Wonderfully complete and logical test you did on the LV and LN shooting planes referred to in your link listed above.

[Derek Cohen]

Thanks George

Derek