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Thread: Scratches on End Grain

  1. #1

    Scratches on End Grain

    Today I went back to trying to sort out a skew mitre plane that I was working on. The original blade wouldn't hold an edge, and I was getting ugly scratches on end grain. I tried everything, and finally gave up and tried another blade. Still the same problem! I set it aside for a month, but went back to it today. Maybe someone can help me diagnose the problem.
    Here is what I get on pine end grain:

    photo 4.jpg

    For comparison, here is my no.4 with a Hock blade.--some faint scratches but nothing I can't live with.

    photo 2.jpg

    And here is the smoother I just made--no scratches.

    photo-163.jpg

    I am sharpening at just under 30°, which is as high as I can go (bed is about 39°). After a number of passes, the iron has lots of very small chips that I can see under a 10x lens. I tried to take a pic but the iphone camera can't focus enough.

    My main thought is that the iron is too hard, so I tempered it to this color:

    photo 1.jpg

    Not sure if the photo is that accurate but I would describe it as gold. Anyway, tempering didn't really seem to help. My first guess is that it is still too hard, but at this point I'm doubting myself and don't know what to think. I'd hate to take this one too far and ruin it, so I decided to ask for advice first.
    Some other possibilities:
    - it's too soft. What would you describe as the characteristics of too soft vs. too hard?
    - There are clearance angle problems. Doesn't seem like that would produce scratches, but I don't know.

    One other thing: they are both Butcher irons, but from different eras, and one was slotted and the other not. Don't see how that would matter, but wanted to mention it.

    Anyway, sorry for the marathon post. If anyone has any great ideas, I'm all ears! Thanks!
    Last edited by Steve Voigt; 07-11-2014 at 10:26 PM.

  2. #2
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    David or someone with more experience than me will have better input, but that's definitely the sort of thing I've seen with chippy irons. (Actually, it looks pretty much like what I got with my Lie Nielsen A2 in my BU jack until I raised the bevel angle)

    With too soft irons, on end grain, instead of that failure mode, I just get an iron that stops cutting way to soon, either needing to be advanced for a heavy cut with a lot of muscle to do any work (although this doesn't work on end grain) or worst case, a folded edge that can easily be felt.

  3. #3
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    Just another thought - this is clean wood, right? I've had similar problems when I've tried to shoot the end grain of wood from the lumber yard right from the store and not on an end I've cut - doesn't take much grit to wreak havoc on your blade.

  4. #4
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    You already know the answer: the steel sucks.

    I don't know how much you know about steel, so pardon me if I state the obvious, but there are so many that don't have a proper understanding, so perhaps a bit of an explanation will be useful.

    Looking at plain high-carbon steel first. Carbon and iron do not normally like each other and do not readily combine chemically. When steel is heated, the clumps of carbon in the mass of iron and carbon (and other impurities) dissolve and spread out. When the steel is suddenly cooled by quenching it in water or oil (traditional method), the carbon doesn't have time to clump back together again, but instead gets locked in with the iron forming a crystalline structure called "martensite." The little clumps of martensite crystals are in turn sometimes called "carbides" by some.

    Interestingly, these crystals take up more volume than the same amount of un-crystallized iron and carbon does, which is why the stresses induced by quenching often cause warping and even cracking. An example of this is the curve in Japanese swords which is formed when the blade is differentially cooled when quenched.

    But there are lots of critical factors to be considered. The amount of iron and carbon needs to be balanced or the steel will be too soft or too brittle. Cast iron, for instance, has too much carbon, and so while it is often hard, it is very brittle. Too little carbon, and we have "mild steel," which is very tough and predictable under stress and so perfect for many purposes, but will not hold a cutting edge for long.

    But even if we have the right balance of carbon and iron, and the mixture is heated and quenched (and then tempered by reheating) at the right temperatures and the right timing, the hard martensite crystals often form isolated islands within the iron mass with rivers and oceans of softer iron surrounding them. In a cutting edge, many of these hard crystalline clumps will of course be front and center cutting wood for you, but the softer iron surrounding them will be quickly eroded, and then even the hard martensite crystals, losing support, will be torn off the cutting edge. Depending on the hardness of the material being cut, the blade's edge quickly becomes ragged, leaving striations on the wood's surface.

    The best steel has always been made by the process of hammer forging (not to be confused with drop hammer forging where metal is slammed into a mold by a huge mechanical hammer weighing tons). Material of the right size and thickness is heated to the right temperature, and then beat the right number of times, at the right locations, with the right force with a hammer, either hand-held or mechanical. The material gradually cools while this hammering is going on, of course. It is then reheated and hammered again, for a total of at least two "heats." This hammer forging process breaks down the islands of crystals into smaller ones, and distributes them more evenly throughout the material. When the material is quenched the last time, the martensite crystals remain locked in place. This process makes all the difference in a cutting tool's performance, bit it is difficult and takes years of experience to learn to do properly and consistently. This is why the term "hand forged" is important.

    A sentence on tempering. Tempering involves reheating the steel to a lower temperature for a short period of time to relieves stresses and to cause some of the martensite to degrade a bit, making the steel softer, but much tougher (less brittle). All this is much easier to say than do, and so the skilled blacksmith has been the most valued of mankind's craftsmen since the time someone tried to block a stroke from a steel sword with a copper or bronze sword. The blacksmith makes everybody else's tools.

    In modern time, we have figured out how to add other chemicals to the mixture to make the process of heat treating steel easier and more predictable. Chrome, nickle, vanadium, molybdenum, tungsten, lead, boron, calcium, copper, manganese, and many other chemicals are sometimes added to improve toughness, abrasion-resistance, corrosion resistance, machinability, and to encourage the crystalline structure to remain fine and evenly distributed. These additives can also decrease warpage and make it possible to obtain a useful steel even if the heat treating and tempering temperatures are a bit off the ideal. But for working wood with tools that are to be sharpened by hand, nothing beats plain high-carbon steel that has been worked with great skill.

    In reality, it's difficult to find new tools made this way anymore since these very effective but traditional methods do not lend themselves to mass-production by Chinese peasants. Needless to say, they are not sold at Walymart or Home Despot. This at least partly explains why so many discerning woodworkers seek out vintage tools.

    So, back to the original problem. The answer is the steel on your particular blade sucks. Re-heat treating will not solve it, because even of you get the temperatures and timing right, everytime the steel is heated, carbon escapes. That is the black skin and scale that appears on the blade's surface. The only fix is to get a better blade.
    Last edited by Stanley Covington; 07-12-2014 at 9:02 AM.

  5. #5
    Stanley: Thanks for taking the time to write this up; I learned something!

  6. #6
    Stan,
    I appreciate the thorough post, but as a former machinist I'm pretty familiar with the structure of steel. That knowledge isn't helping me a lot with this specific problem; however, I'm sure others will find your information useful.
    Regarding the steel "sucking," I'm not sure I understand your point. You say that hand-forged, high-carbon steel is the best. As I mentioned, this is a Butcher iron, probably mid to late 19th C. Like all irons of that era, it is simple water-hardening steel, very similar to W1 or 1095, and not much different from your Japanese White. Like all tapered, laminated Western irons, it was forged; probably with a trip hammer rather than by hand, but pretty close (and I've seen plenty of videos of Japanese smiths using trip hammers). Butcher was also the dominant maker of the time, and well-respected. So, to clarify: are you saying that all irons of this type "suck," or are you suggesting that this particular iron is defective? I've definitely considered the possibility that it's the latter, but I'd like to keep trying before I throw in the towel and get another iron. If you're saying it's the former, we'll just have to agree to disagree. The third pic I posted is also a vintage forged, laminated iron, though probably a little later, and it seems to be doing ok.

  7. #7
    Quote Originally Posted by Joshua Pierce View Post
    … that's definitely the sort of thing I've seen with chippy irons. (Actually, it looks pretty much like what I got with my Lie Nielsen A2 in my BU jack until I raised the bevel angle)

    With too soft irons, on end grain, instead of that failure mode, I just get an iron that stops cutting way to soon, either needing to be advanced for a heavy cut with a lot of muscle to do any work (although this doesn't work on end grain) or worst case, a folded edge that can easily be felt.
    Josh, thanks, this is very helpful. I guess I'm lucky in the sense that almost all the irons I've used have been pretty good, so I don't have a great sense of how quantifiable defects actually play out at the bench.
    On your other post--yes, the wood is clean; I repeated this test with the 3 planes several times, and tried a board of soft maple too. The results have been very consistent.

  8. #8
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    Steve:

    I am not condemning Butcher irons, much less all such "types." But obviously the one in question is not up to the job. The Hock blade clearly has it beat hands down.

    I am not condemning any old irons. I have several old irons made in England in the 1800's I cut down and used for planes. Some suck and behaved just as you described yours does. At least two of them cut like the very devil. Excellent irons.

    There are Japanese blades that suck too. Mostly for the reasons I described. Quality control is difficult in any situation. Modern materials and methods (at least outside of China) produce mediocre performance, but cheaply and very consistently.

    But you know what they say about sows ears, and silk purses. Just my opinion and an attempt to share what I learned and concluded when faced with the same problem.

  9. #9
    First you need to know that the edge really has nicks. Did you look under magnification? Before and after sharpening? Before and after cutting? You can also often feel them with a fingernail, but optical magnification is much more precise. It doesn't have to be a microscope, I can see nicks with an 8x loupe, long after I can't feel them anymore.

    I don't think it could be something else then nicks in the steel, but you have to be sure first. And I'm afraid I can't help you much further, because i don't know enough about metal to give a cure for a bad blade.

  10. #10
    I think it's a matter of the steel being at 29 degrees and maybe preferring another 3 or 4 degrees on the skew. I haven't found any steel of any type that won't eventually chip while wearing when it's below about 33 or so degrees - esp if the wood includes hardwoods and softwoods. It's just a matter of how much you can tolerate.

    I wonder if you added literally four or five strokes on a polish stone around 35 degrees if you'd have too fat of a profile for the plane to still cut OK.

    At this point, I use planes with a 45 degree bed for everything, so I haven't thought about this for a while. When I used japanese planes more, I was keeping the final bevel around 28 or 29 degrees, and it always drove me a little bit nutty because on hardwoods, a japanese iron will still have minor chipping, and the entire purpose when I was using a japanese plane was to get a bright uninterrupted surface. They are also less convenient with large nicks, but the small ones usually come out in a normal sharpening process.

  11. #11
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    If two different blades on this plane do it, and your other planes don't, have you considered the possibility that it's not the blade but the sole of your plane that's scratching the stock?

  12. #12
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    I know those scratches, chippy iron. My A2 blade in the LV apron plane will do that same unless freshly sharpened, which is why I want to try a PMV11.
    I would try David's suggestion and give a tiny micro bevel on your last stone.

  13. #13
    Steve, if you have two different Butcher irons and both give problems, I doubt it is the steel.

    One thing I thought of is that if you measure the 39 degree bed along the side of the plane, the bed angle when measured perpendicular to the mouth would be slightly higher. For a 15 degree skew (measured along the bottom of the plane) the effective angle measured perpendicular to the mouth would would be 39.97 and for a 20 degree skew the effective angle would be 40.75. So you may have a little more clearance than you had thought and could slightly raise the bevel angle.

    I would also spend some extra time sharpening compared to your normal routine to get beyond small flaws that you cannot see. Both on the bevel and the back. Also I would spend extra time stropping on a clean hard piece of leather, back and forth.

  14. #14
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    If your Butcher iron was properly hardened to begin with,heating it to a gold color(a darkish straw) isn't going to soften it. It was heated to a darker color originally,to begin with.

    It is easy to see if your blade is too hard:Test it with a fine cut file in good condition. I have said here several times that while using antique planes for the many years I was in costume,I found that the most durable irons were the ones that I could barely file with a new,sharp Nicholson file. Of course,these days,unless you have an old USA made Nicholson,that will mean nothing. A butter soft Mexican Nicholson is not going to tell you anything.

    I'd first experiment with grinding your blade at a less acute angle to see if that strengthens the edge,preventing the micro chipping that is probably causing your scratches. If all else fails,and your iron is too hard to file,I suggest heating the iron to a dark brown color.

    Getting a durable edge is a balancing act between hardness and toughness. I seriously doubt that your blade steel sucks.

  15. #15
    Thanks to everyone who chimed in; I really appreciate the suggestions.

    George: You're absolutely right about the gold color not being hot enough; I was just being cautious--didn't want to go to far. I did retemper to a purple-gold color, but that didn't fix it, and I'm reluctant to take it any farther. However, as a side benefit of this project, I did learn to temper more evenly, which I'm happy about. You have written many times that oven tempering can be problematic, and it definitely has been for me. This time around, I tempered on the stove top, and was able to get a much more even color. I should stfu and listen to you more often!
    The file trick has never worked for me, George. The main problem is that any good file I have is well broken in. But I did have success trying to scratch the backs of several irons with a carbide scribe, and comparing the results. This showed me that the Butcher was actually a little harder than the Hock, so way too hard. It's a little softer now, which is why I'm reluctant to temper more.

    David: I had already tried a tiny steeper microbevel, and it didn't help. But I think I agree with you about bed angles. My smoother, which is pitched at 50°, outperformed the other two planes on end grain, and is not remotely hard to push. But you can't shoot with a coffin plane!
    That led me to the solution, though. I gave up on maintaining the low angle and started back-beveling the iron. I'm not crazy about back bevels, but it beats consigning the plane to the plane graveyard in my basement. I bet you have one of those.
    Anyway, the scratches mostly disappeared at 4°, and completely disappeared at 6°. Which leaves me with an included angle of …45°! Doh! If I could do it over again, I'd bed the plane at 45°. Live and learn.

    Stanley: I don't think the iron sucks, but it is true that steels like W1, or your Japanese white, are less tough than O1 or Japanese blue. And end grain is very hard on edges. In retrospect, an O1 iron, not vintage, might have been a better choice.

    Joshua and Mathew: You guys were definitely right about steeper bevels making the scratches go away. It just took me awhile to get to the back-bevel idea. Thanks!

    Warren: I don't have a proper leather strop, but you've convinced me. I'm going to get one from Joel before the summer is out. Your point about spending extra time sharpening is well-taken.

    Kees and Alan, thanks for your suggestions. It was definitely the angle, but it was good to rule out all other possibilities.

    Thanks again folks!

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