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Is it me, or is it the usuba? - Page 2
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Thread: Is it me, or is it the usuba?

  1. #11
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    JBroida's Avatar
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    that is also very true... on really wide bevels, you notice pressure changes more. The place where your fingers are above is where the bulk of sharpening takes place, so you may end up with things that look like high and low spots based on not moving your fingers around enough. Light pressure minimizes this, but its still true.

  2. #12

    echerub's Avatar
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    Yeah, and that's something I'm a little concerned about. If that is the case, then it's a good thing it's showing up for me with the econo-usuba and not a nicer one

    Well, I'll take a close look at the knife later on...
    Len

  3. #13
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    Quote Originally Posted by echerub View Post
    Yeah, and that's something I'm a little concerned about. If that is the case, then it's a good thing it's showing up for me with the econo-usuba and not a nicer one

    Well, I'll take a close look at the knife later on...
    You should take it with you to Tosho or knifetoronto (or both even better) and let them take a try with it. Easy second and third opinions and cheaper than buying another if it isn't necessary

  4. #14

    echerub's Avatar
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    I don't know if my eyes are playing tricks on me - it's such a fine edge - but I think there is a bit of lateral waviness going on. Looking from heel to tip, the middle of the knife curves a little to the right compared to the portions immediately before and after it. The heel and tip are out of focus and doing funky things on me. Astigmatism sure doesn't help when I'm trying to eyeball a thin thin edge like this

    But if I trust my eyes and it's not just my brain doing some wishful thinking, that slight waviness would make sense. It would put the "arched" areas further "down" compared to the middle of the M. Hence, when sharpening on a flat stone those "down" areas will necessarily wear more.

    Yeesh. Man, now I'm *really* starting to get a sense of how freakin' difficult it must be to make these things right!
    Len

  5. #15
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    I totally know what you are going through. I have a usuba that when I first started sharpening I was using way too much force and my blade was very wavy. I ground it flat and resharpened and still wavy. eventually I learned to reflatten the blade, and sharpen it very very slowly and with light pressure and it worked. Occasionally after sharpening now I will hold it up to the light and see some slight wave but I just let it slide now.

    But I remember those first few times I kept holding the knife edge up to windows, lights, rulers, the wall, any flat edges I could find in the apartment (I couldn't find anything perfectly straight!) and my eyes were dry as chalk.

  6. #16
    Mike Davis's Avatar
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    I will also add that it might be a heat treat issue. If you have hardness zones, even if it only varies by 1-2 rc points, it could cause issues. You could theoretically bend the edge by applying pressure when sharpening....If the HT is shot, it might flex and stay flexed. Just another thought to drive your current insanity.

  7. #17

    echerub's Avatar
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    After a brief chat with the Wizard Out West (that'd be Jon ), I've got a bit of a task ahead now: trying to straighten out edge warpage

    Thank goodness this is a for-fun knife and not one that I'm relying on...
    Len

  8. #18
    Senior Member Seth's Avatar
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    I have a 240 nenohi kama usuba; a big beautiful knife for sure. I had some waviness and started checking the geometry against the quartz counter. With back side down there is a slight rise at the curved part of the spine - distal. Flipping over, the blade road is dead flat. I figured then that this was technique. On flat stones I did the blade road longitude direction with light pressure only in areas where the edge humped. I use a microbevel on this knife as well and worked that gently as well. I was able to get the edge fairly straight and over a couple more sessions it should improve. For those lusting after good usubas this is an argument for sticking with 180s or 195s as I expect these would be easier to deal with.
    Seth

  9. #19
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    I've gotten this before, and I have to say I've never successfully straightened an edge with an "n" or "m". Last time I tried, I destroyed my knife, LOL. It was like the knife was cursed! This is something I always check when buying new knives now cause dealing with such a problem is a huge pain. The only thing I would recommend is keep on grinding away properly, and don't get frustrated and screw up your knife chasing your "m" shape.

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