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Thread: Problems sharpening/using PM-V11 blades

  1. #16
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    The more experience I get under my belt, the less I like Powdered Metal blades. There is no free lunch, and in this case you are giving up sharpness for edge durability. Personally, I would prefer to sharpen more often to get a sharper edge, rather than have the same blade last longer. Especially when you become more comfortable with sharpening. That said, pmv steel does seem to last quite a while in my BU Jack when just flattening and edge jointing. But for chisels and final smoothing, I'll take O1 or Japanese steel any day of the week

  2. #17
    Good point on the thickness of the blade reducing my cambering Derek. The shaving posted was full-width from the edge of a board, so there was no feathering happening. I haven't tried the newly-sharpened 50 deg blade on a wide surface yet to see if it leaves tracks, I'll give it a go later and see.

  3. #18
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    Quote Originally Posted by Marty Schlosser View Post
    Brian,

    At the sake of sounding as though I'm disagreeing with you, I'll state that one only has to grind back far enough to ensure that the secondary bevel will be fully in new metal. In most cases that means that there is no need to grind all the way back to the primary bevel.
    No worries Marty, and you are correct. However, talking about two different but similar goals. My reasoning for suggesting the small bevel is quite simple, it's easy to hone and being easier to hone it will be more accurate, especially when done by hand. It's difficult to repeat your microbevels free hand, so if you remove them or minimize to the point of near reduction then their replacement will be accurate.

    So even when I do not remove the microbevel, I will grind on the primary until the microbevel is very small.
    Last edited by Brian Holcombe; 11-30-2015 at 10:32 PM.
    Bumbling forward into the unknown.

  4. #19
    Occasionally I do grind a hollow to remove a large secondary/tertiary bevel using my 8" slow grinder, being careful not to overheat.

  5. #20
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    Quote Originally Posted by Mike Cherry View Post
    The more experience I get under my belt, the less I like Powdered Metal blades. There is no free lunch, and in this case you are giving up sharpness for edge durability. Personally, I would prefer to sharpen more often to get a sharper edge, rather than have the same blade last longer. Especially when you become more comfortable with sharpening. That said, pmv steel does seem to last quite a while in my BU Jack when just flattening and edge jointing. But for chisels and final smoothing, I'll take O1 or Japanese steel any day of the week
    Mike, powdered metal blades theoretically should provide the finest edge. They do this in practice as long as you use the appropriate honing media. If you cannot do this, then stick to steels that suit your media. The durability of PM-V11 is especially apparent in chisels, where they are almost on par with Japanese white steel, and both are in another class to A2 and O1 in regards edge holding. But without the appropriate media (diamond, ceramic waterstones), they will not produce the edge they are capable of.

    Regards from Perth

    Derek

  6. #21
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    Thanks Derek, that's a great point. In my case, I do have diamond stones up to 1200 then I go shapton 2k and naniwa Snow White 8k. That is what you seem to suggest and I admittedly get a good edge, I just find I get a better edge with other metals(O1 in particular). For all I know, it's all in my head. I defer to the more experienced folk like yourself. As I mentioned, it definitely holds an edge for a good while. I sharpen often so I guess that is why the pmv seems wasted on me.

  7. #22
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    Quote Originally Posted by Derek Cohen View Post
    Mike, powdered metal blades theoretically should provide the finest edge. They do this in practice as long as you use the appropriate honing media. If you cannot do this, then stick to steels that suit your media. The durability of PM-V11 is especially apparent in chisels, where they are almost on par with Japanese white steel, and both are in another class to A2 and O1 in regards edge holding. But without the appropriate media (diamond, ceramic waterstones), they will not produce the edge they are capable of.

    Regards from Perth

    Derek
    Hi Derek,

    Will regular waterstones not do an adequate job on PM-V11?

  8. #23
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    Quote Originally Posted by Phil Stone View Post
    Hi Derek,

    Will regular waterstones not do an adequate job on PM-V11?
    PM-V11 will hone on most media from oil stones to ceramic waterstones, and between. It is just that some media will hone it more efficiently than others. With the less efficient media the danger is not doing a complete enough job, that is, stopping short of scratch removal or working to a wire edge. To increase the chances of a good sharpening one adds in method, and here the best recommendation is to reduce the blade area to a minimum. That is, work with a microbevel - either as a secondary bevel created on a honing guide or, as I prefer, a on a hollow grind, which allows one to freehand the bevel.

    Regards from Perth

    Derek

  9. #24
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    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.

    On a tangential note, it's interesting that Veritas came out with something called "PM-V11" not long after Crucible's patent on "CPM-11V" ran out. The material properties appear comparable, and Crucible's copyright/trademark remains enforceable (those run for a lot longer than patents) which would explain the different name.

  10. #25
    Interesting to hear, Patrick. Thanks to everyone here for helping me find my sharpening problems with this steel. Amazing it takes 2-4x more work than A2 for sharpening on Shapton stones, but that kind of wear resistance makes for a good plane steel. I currently have PM-V11 blades in my Stanley No. 8C jointer, veritas edge-trimming planes, shooting plane, skew rabbet, and skew block planes (and my replacement LA jack blade mentioned in the first post). And now that my sharpening on them isn't quite so hit-or-miss, they should work even better.

  11. #26
    Quote Originally Posted by Patrick Chase View Post
    On a tangential note, it's interesting that Veritas came out with something called "PM-V11" not long after Crucible's patent on "CPM-11V" ran out. The material properties appear comparable, and Crucible's copyright/trademark remains enforceable (those run for a lot longer than patents) which would explain the different name.
    That's an interesting comment. I always assumed PM-V11 stood for "Powdered Metal, Version 11".

    Mike
    Go into the world and do well. But more importantly, go into the world and do good.

  12. #27
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    I've read enough old threads to know that this has been hashed over ad-nauseum and I'm not contributing anything new, but:

    There is a fundamental tradeoff in stone design between hardness (and therefore dish resistance) and sharpening speed with difficult steels. Stones slow down when the abrasive particles are retained long enough to become dull. The "sweet spot" for any given metal (O1, A2, PM-V11, PM-HSS, etc) is therefore a stone that's just soft enough to release the abrasive right as it starts to dull. If the stone is harder than that then it will cut slowly. If the stone is softer then it will be uneconomical because it prematurely sheds perfectly good abrasive, and a pain to maintain because it goes out of flat quickly.

    I'm an unreformed stone whore who owns a bunch of Shapton Pros and a sizable hoard of PM-V11 blades, and in my experience all but the 120 and 320 Shaptons are harder than ideal for PM-V11 and prone to slow cutting. In my opinion Stu's Sigma Powers are right about at the sweet spot for PM-V11, while Sigma Select IIs are too soft (though they're spectacular on PM-HSS...). For that matter I prefer Besters to Shapton Pros for PM-V11.

    Technique also matters - A good technician can extend the "sweet spot" of any given stone in both directions by varying pressure, speed, honing pattern, and surface wetness, so I don't doubt that somebody will pop up and rightly claim they can cut PM-V11 at full speed on Shaptons. At some point you have to decide how much time and effort you're willing to spend optimizing your waterstones as opposed to just buying a softer set and spending those brain cells on actually working wood instead.

  13. #28
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    In the case of CPM-11V it stands for "11% Vanadium".

    Note that a conventionally processed (non-PM) steel with that much Vanadium would likely end up a grainy mess of carbides.

    The original patent covering CPM-11V is http://www.google.com/patents/US4249945 and ran out long ago, but there are subsequent patents up to ~1991 that might be necessary to actually manufacture high-quality parts (I have some academic training in metallurgy, but it's been an awfully long time and this is relatively advanced stuff). Those ran out shortly before PM-V11 hit the market.

    Does anybody out there have a mass-spec machine and a PM-V11 blade they'd like to sacrifice?

  14. #29
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    Patrick, Welcome to the Creek.

    I am always curious as to the area of the world one calls home.

    Thanks for sharing your information on steel and stone. Good explanations in compact form.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  15. #30
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    Location fixed

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