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  1. #1
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    Default Plane blades: hard, tough or brittle??

    OK, so this is not put up as a scientific experiment, or any attempt to disparage the new powder-metal blades, but I thought it interesting enough to share & invite comment.

    A couple of days ago, I was making a pair of 'rustic' benches for SWMBO to keep some of her potted plants on. The woods I used were Spotted gum (which was surprisingly 'soft' for SG), and some Blue gum (or Forest Red gum as it's known further south - E. teriticornis), which I'd slabbed out of a decent-sized tree a neighbor gave me a couple of years ago. I used 3 hand planes in the process, my workhorse 5 1/2 equipped with a LV HSS blade, a #4 with a PMV11 blade, and a LV Low-angle smoother with an A2 blade. The 5 1/2 was used most, and felt pretty dull by the time I'd finished - I should have stopped & sharpened it, but you know how it is when you are hurrying to finish something. The #4 got about 2/3rds as much use and the LA smoother a bit less again. By the time I'd finished, the PMV11 blade was not coping too well at all. Here is a bit of scrap I ran it over a couple of times: scratched wood.jpg
    Not a bad imitation of a toothing iron!

    The blade edge looked like this: PMV11 red.jpg

    The A2 blade, which had done a little less work, but not much less, looked like this: A2 red.jpg

    While the HSS blade, which travelled twice as far, at least, as the other two, looked like this: HSS red.jpg

    It was dull, make no mistake, but just dull, with virtually no chipping!

    The PMV11 is the worst of the 3, by far, the gaps on the A2 edge were only about half as deep. The annoying thing is that of the 3, the darned HSS blade was the only one in need of a bit of a re-grind, when I started. I was able to clean up the two chipped blades by hand-honing on coarse diamond plates fairly quickly, but it was a bit of a heads-up for me. Both blades are ground & honed to manufacturer's specs. However, the recommendations clearly weren't made with woods like our Blue gum in mind! To give the PMV11 blade its due, it does hold an edge a very long time in most woods, even She-oak, which is a notorious blade-duller, doesn't cause this sort of damage.

    However, it does add a bit more to my waning love of super-hard steels. For my first 35 or so years of woodworking, I was always chasing harder blades. My first experience of the HSS blades Stanley Australia made was a revelation - they would hold an edge at least twice as long as the old carbon-steel blades. Then along came A2, with its promise of even better edge retention, & eventually, PMV11. Heaven on a stick, you'd think. Well, so far, I'm not as thrilled with either as I thought I would be. I've decided I could live without A2 for chisels, particularly - I'd rather have slightly less hardness & be able to keep the grind/hone angles lower. The brittleness of the PMV is rather alarming, though - don't think I'll feed that one to Blue gum again in a hurry....

    Cheers,
    IW

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  3. #2
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    There's always a trade-off between toughness and hardness. My understanding is that M2 HSS is the way to go now if you want maximum edge retention (at the expense of needing a fair bit of work to re-grind).
    What was your bevel angle? Might be worth adding an extra 5 degrees as a secondary bevel if you're doing a lot of work in hard timbers.

  4. #3
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    Quote Originally Posted by elanjacobs View Post
    There's always a trade-off between toughness and hardness. My understanding is that M2 HSS is the way to go now if you want maximum edge retention (at the expense of needing a fair bit of work to re-grind).
    .....
    Elan, that's always been the maxim I live by, too. However, one of the claimed advantages of PMV11 is its high impact resistance, which in my mind equates to toughness. The blurb from LV on this stuff implies you can have your cake & eat it too, but it seems like you can't. I wasn't surprised this wood dulled any of the blades, I was surprised to see it had chipped more severely than the other two alloys.

    Quote Originally Posted by elanjacobs View Post
    ...What was your bevel angle? Might be worth adding an extra 5 degrees as a secondary bevel if you're doing a lot of work in hard timbers....
    Good point, I forgot to mention that. Can't tell you the exact angles, but they were all similar. The blades would all have been ground to something a tad above 25 deg., & the honing bevels would have been around 30 or more, because each blade had been honed multiple times, and being a freehand honer, my angles creep up between re-grinds. There may have been a degree or two difference where the rubber hits the road, but all were well within the manufacturer's recommendations. Increasing the honing angles a bit more might help, though I wouldn't go above 35 max on a bevel-down plane, because I reckon you need at least 10 degrees of clearance behind the cutting edge on a plane.

    However, I'll stick with my current sharpening angles for now. All of those blades do just fine on the woods I normally use a plane on. Semi petrified wood like this is reserved for garden beds or fences, as a rule, so it's not an ongoing problem. I certainly won't be feeding my planes to it again in a hurry! Being a bit less fit & strong than I used to be, planing Maple or Cedar is a much more attractive prospect, these days......

    Cheers,
    IW

  5. #4
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    Hi Ian

    I would consider returning that PM-V11 blade, but first try grinding it back 1/16". It seems to be too hard at the edge (common among many new blades). Keep in mind that I have used many of these blades, and have not had your experience.

    The real/biggest advantage of PM-V11 (in my opinion) is with chisels. This steel has excellent impact resistance - which is why chipping is unusual. With regards planing - in other words, abrasion resistance - I would argue that PM has about 50% (not twice) the longevity of A2, which in turn has about twice the longevity of O1.

    One of the great things about PM steel is the fine grain structure. It creates an edge that is similar to O1. Both A2 and M2 (HSS) have coarser grain structures than both PM and O1.

    If you want an example of the impact resistance of PM steel, then read my review of the LV Shooting Plane, where I compared A2, PM-V11, and O1. Bed angles affect blade longevity (lower bed angles reduce wear), but the advantage of the new PM steels (V11 and M4) is clear to me.

    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.

  6. #5
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    Admittedly I've made a fraction of a fraction of an afterthought of the number of plane strokes as the others who have commented on this thread, but I didn't really think that they were supposed to chip like that without snagging nails or some other form of extreme gnarliness... Like Derek, I haven't seen that kind of chipping (Except when I accidentally plane my brass bench dogs...) and I have several PM-V11 blades.

    I'm sure you know this, and derek alluded to it too, but sometimes you have to grind more than just a sharpening's worth off the bevel to get the steel off of the blade that has been weakened by heat treating. The PM-V11 wasn't brand new was it?

    Since we're on the topic of plane blade material and you didn't mention it... What do you think of 0-1 plane blades? I've got some PM-V11 blades and some A2 blades and I was thinking about throwing an 0-1 blade from Hock into my recently refurbished stanley #7 so I could make some more empirical judgement about the three for myself. Still interested to hear others' opinions.

    Cheers,
    Luke

  7. #6
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    I've always liked Hock blades. They sharpen very smoothly I've noticed and relatively quickly compared to other blades I've noticed. With small spokeshave blades there tops. Because I can sharpen very quickly, straight on the grinder then buffing wheel. I never have any anxiety burning them. They don't seem to suddenly overheat on me. And edges hold up better for me. Don't seem to get deep chipping of the blades when they dull.

    I find the way he describes it not too overcomplicated as well. over complication is not smart/clever/intellegent imo.
    http://www.hocktools.com/tech-info/toolsteel.html


    some kind of fear filled disclaimer ->……. in no way am I associated with his business. I am not trying to increase his sales. I don't even know him. I've never met him. who knows what he's like. He's probably a nice guy, but maybe he's hiiiiiiiding something. maybe…….look, I just like his blades.

  8. #7
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    Derek & Luke - all good points. It was indeed a great surprise to me to see how severe that chipping was. I didn't hit any metal, or grit, I'm quite certain of that, because I was planing surfaces that had already been through a thicknesser. This is a very siliceous wood, for sure, so I would've expected to see even dulling, not chipping, on a 'tough' blade. The blade isn't new, but it has had very little use 'til recently. It has been ground once, very lightly, since I got it, and I doubt I would've brought the factory edge back more than .5mm at the most. So p'raps a moderately heavy regrind is the first action I should take. I was aware of the edge brittleness issue on new A2 tools, but didn't know it could be the same for PMV11.

    I suppose I should also see to it sooner rather than later. Unfortunately, I've had this blade a bit over 2 yrs, so it's rather late to lodge a complaint, perhaps. Hard to see how it could be a dud - the claimed advantage of the powder metal process is supposed to be very consistent quality & LV are usually pretty tight on their QC. Maybe someone looked the wrong way at the wrong time. Some may remember I whinged about how difficult this blade was to put a decent edge on, when I first got it (it was this blade that forced me to try water stones again!). This surprised me at the time, because Derek had said in his early review that PMV11 was no harder to sharpen than A2, but this blade is definitely harder by a good margin than my A2 chisels. I could put an edge on them with Arkansas stones (not easily), but there is no way they will cut the mustard with this PMV11 blade. When I get a bit of time to muck about with it, I'll try increasing the bevel angle as high as I'm prepared to tolerate, then feed it to some more of that metallic Bluegum. If it still chips, I'll grind a couple of mm off it & try again, as advised. If it still chips, it's definitely time to consult Mr. Lee.....

    Hard blades are something of a paradox, for me. Conventional wisdom goes something like this: The harder the blade, the longer it holds an edge, therefore less frequent sharpening is required. Most of us aren't madly keen about sharpening, so it seems like a no-brainer to seek out the hardest edges we can find, to stretch out the intervals between that chore. But there's a small flaw in this logic, imo. Think about carbide saw blades - they dull very gradually, & you hardly notice it, until one morning you find yourself going blue in the face pushing smoking wood through your saw. (Slight exaggeration, but you know what I mean. ). It's the same with a plane, the slower the blade dulls, the more time you spend working with sub-optimum sharpness. When a tablesaw motor is burning the calories, I don't mind so much, but these days my body soon lets me know it ain't happy pushing slightly dull planes through hard woods. So like Jake, I'm also a great fan of Mr. Hock's blades. The ones I have really hit that Goldilocks spot between ease of sharpening and durability. When the performance starts to drop, it does so at a noticeable rate, and because they are so easy to refresh, I tend to go to the stone sooner rather than later. It seems to me I'm working with an optimally sharp blade more of the time than I do with harder blades. And I have no company affiliations, just another satisfied user.

    Cheers,
    IW

  9. #8
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    Quote Originally Posted by IanW View Post
    The ones I have really hit that Goldilocks spot between ease of sharpening and durability. When the performance starts to drop, it does so at a noticeable rate, and because they are so easy to refresh, I tend to go to the stone sooner rather than later. It seems to me I'm working with an optimally sharp blade more of the time than I do with harder blades.
    same wavelength I think.

    I don't know if I've got a short attention span(SAS), or a poor memory(PM)…or both, BUT, as soon as I see a deep chip in a blade I get that deeply sad feeling that says…….

    'it might one of those days again'…..

    cause by the time I've got back from sharpening out a deep chip in a super hard and often expensive blade, I've forgotten what I was doing when I noticed the chip…..

    IMO, It really is a big deal forgetting what your doing….or getting out of a good groove…. a good groove or rythym makes or breaks hand work imo. There's too many ways to make a mistake.

    I think you'd understand, but if I told someone else maybe not into this sort of thing, they maybe think I was winging.

    not an expert on grooves ,rhythms, SAS, PM or anything else I didn't abbreviate.

  10. #9
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    Hi Ian. Do you think it possible that the hollow grind has played some part in weakening the strength of the steel at the very cutting edge. Would the cutting edge have chipped so easily had the iron remained a flat bevel.

    Stewie;

  11. #10
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    The final angle needs to be increased on those irons. Doing so is a solution both for irons too soft and too hard (too hard irons will still fail at the very edge very quickly). I haven't yet found any wood that troubles a plane with a final bevel angle of 35 degrees unless it actually has abrasive or dirt in it, but I have often seen people complain about using A2 irons at 30 degrees - I had the same experience. They develop microchipping that leads to early failure unless the bevel is at least low-mid 30s, and then at that point, they will instead last as a smooth edge until the clearance is gone.

    I chased the fantasy blades for a long time, but have gone to vintage irons in general out of preference for sharpening them. The fantasy blade idea had me scared that I'd be sharpening the old irons too often, but that was a matter of not taking a chip thick enough. I do a lot of hand planing, and there isn't a vintage iron that I have that can't wear me out first when used properly. Used the way I used to use irons, no iron wore me out before it had to be resharpened.

    I hollow grind all but my japanese irons but have no problem with any iron unless the final angle is too small. The facet of bevel between the edge and the hollow only has to be very very small, even with a bevel hollow ground at 25 degrees, to prevent damage.

    My experience as above has been the same for chisels. Chisels that I thought were just poor quality in a lot of cases just needed another two degrees. In the last three and a half weekends, I threw together a bench (out of ash, which is relatively hard for us but not for you guys) and did all of the chopping work on the mortises and shoulders with a stanley 720 that I wrote off in my younger days as junk - without resharpening. I would've mangled the chisel in my early days, sticking strictly to the angle that my best chisels held at. Same with plane irons. The difference between where the "good" ones and the "bad" ones hold an edge isn't very much.

    I used the same chisel to mortise two cocobolo planes last year. Same idea. Initial problem was me not observing what the tools like.

    Slowly getting around to the point being that I think the differentiation between all of these various steels is marketing and manufacturing convenience, and not actual improvement in reduced time maintaining tools. I tried them all, though, and still have Tungsten HSS chisels as well as well as two powder metal (m4) chisels.

  12. #11
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    Quote Originally Posted by planemaker View Post
    Hi Ian. Do you think it possible that the hollow grind has played some part in weakening the strength of the steel at the very cutting edge. Would the cutting edge have chipped so easily had the iron remained a flat bevel.

    Stewie;
    Stewie, I wouldn't think so, because my secondary bevel was quite wide, and I doubt making it any wider would've made a difference to the strength of the edge. As a partial proof of my argument, none of the chips extends more than halfway into the secondary bevel. I will never be weaned off hollow-grinding - it saves too much time & elbow-wear!

    I agree with DW in that you need to pay attention to the secondary bevel and adjust according to the steel type AND the wood you are planing/chiselling. I may have to revisit grinding sharpening angles on the PMV11 blade, though. At least for some woods, the recommended angles are obviously not steep enough. However, the easier way may be to simply not use this blade on such recalcitrant material. That won't be too difficult, because as I said, it's far more appropriate for making garden beds than fine furniture!

    I pretty much agree with his attitude to very hard steels, too, with some reservations. There is no doubt in my mind that harder steels wear far better with many of our abrasive, highly siliceous woods than the older, softer steels, but it isn't black & white. It obviously depends on how much impact they have to tolerate, to a large extent. Last week I was pounding my old Titan firmers (plain old HCS) into some very tough Bluegum, and they stood up to it amazingly well, I had to touch up a couple of times whilst chopping 8 large mortises through 2.5" thick stock, but there was not a hint of chipping. A few strokes over the fine stone put the gloss back on them each time. Had I used my A2 chisels for the same job, with the same (fairly low) bevel angles, it would have been a very different story!

    If you use your tools enough, you get used to the idiosyncracies of each, including what sharpening angles work best in what situations. This is one reason I keep a few more planes & chisels around than I really need - it isn't practical to keep altering sharpening bevels every time I change woods, so I keep enough set up to cover common situations reasonably well, if not optimally. You could take this philosophy to extremes and end up with a ridiculous number of duplicate planes & chisels - I was tending that way, until a shred of commonsense crept in....

    Cheers,
    IW

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