Altering profile of Takeda bunka

Discussion in 'Sharpening Station' started by Viggetorr, Dec 1, 2019.

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  1. Dec 1, 2019 #1

    Viggetorr

    Viggetorr

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    I have a NAS Takeda bunka with a profile that I find a little to rounded for my taste. I'd like to be able to chop garlic, for example, but given the constant curve of the edge it leaves the edges of the garlic intact.

    I'm thinking about putting it to my coarsest stone (Shapton Glass 220) and simply adding a flat spot in the middle by grinding away. Is this a good idea or will I risk messing it up?
     
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  2. Dec 1, 2019 #2

    labor of love

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    Altering the profile means you would likely have to also have do thinning as well. Thinning a takeda is not an easy task.
    Seeing as Takeda has a low bevel, changes made will likely effect how the knife performs a bit more drastically than say something more conventionally ground.
     
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  3. Dec 1, 2019 #3
    It is going to be a lot of work that will take several hours. I am not saying that you should not give it a go, but swapping it for one that fits you better could save you a lot of work.

    I recently did some thinning on my Takeda NAS nakiri (has also a lot of belly on both ends, but I like it) and yeah, it was quit some work just to thin it a bit
     
  4. Dec 1, 2019 #4

    labor of love

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    Side note: takeda does do direct orders...personally I think a lot of stuff they produce that’s off the shelf has too much belly for me. You can request a flatter profile or better yet find an old school flatter profiled takeda photo, send it to them and ask them to reproduce it for you. In the past I’ve had very good results going the direct route.
     
  5. Dec 2, 2019 #5

    Viggetorr

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    Thanks for your input!

    Maybe I simply don't understand, but to me the thinning doesn't seem like an issue as you automatically thin a Takeda when your sharpen it. It doesn't get fatter towards the spine like most knives, and if you retain the zero ground bevel thinning shouldn't be needed?
     
  6. Dec 2, 2019 #6

    ian

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    Say you alter the profile by grinding away at the middle part of the edge (not the whole bevel, just the edge) until the profile is more flat. Then the knife will be much thicker behind the edge in the middle of the blade than it will be toward the extremities. Also, the shinogi won't be parallel to the edge anymore: it'll be closer to the edge in the middle.

    But maybe you're suggesting just laying the blade flat on the bevel and grinding mostly in the middle part of the blade, instead of as above. I guess that will work, and probably most people would call that thinning. Might be a little tricky to get the profile perfect without (or even with) some bread knifing, though.
     
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  7. Dec 2, 2019 #7

    Dendrobatez

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    Working on takedas is a huge PIA I'm not sure how the grind is on the NAS ones but the old ones I own had pretty apparent scandi grinds. Changing the profile in one spot without thinning the entire thing would make it perform wonky afterwards. Again I know I've seen some from a few years ago that were more flat ground so it depends on which you have
     
  8. Dec 2, 2019 #8

    labor of love

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    Think of it this way, if you remove metal from the edge then that means the distance from edge to shinogi becomes closer than it was made to be. Not only do you have to thin but you have to raise shinogi in the areas where the profile was modified to maintain the geometry.
     
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  9. Dec 2, 2019 #9

    Viggetorr

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    [​IMG] [​IMG]
    Yes, maybe I was unclear: given that the bevel is so low and it comes with a zero grind from the factory I always lay the entire bevel against the stone when sharpening it. So I guess that's both sharpening and thinning at the same time, while maintaining the geometry and distance between shinogi and edge.

    ian, what do you mean by "bread knifing"?

    Yes, mine has a scandi grind, so I always thin when I sharpen it. See pic below.[​IMG]
     
    Last edited: Dec 2, 2019
  10. Dec 2, 2019 #10

    ian

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    Breadknifing is the term people seem to use around here for altering the profile by trying to saw through your stone, like you would use a bread knife to saw through bread. It’s a useful technique, since it’s sometimes hard to get that nice continuous curve otherwise. It’s a terrible term though. I was convinced it meant producing serrations initially.
     
  11. Dec 2, 2019 #11

    labor of love

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    Thinning will not raise the shinogi line, you will very likely have to reestablish a new shinogi line. For takeda knives this is not an easy task. I dunno, maybe you can get away with not doing this...but in order to maintain the geometry after removing and altering the edge you have to raise the shinogi line higher up the blade than where it’s at presently, thus raising the blade road.
     
  12. Dec 2, 2019 #12

    ian

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    Hmm, won't it, though? If you place your blade so the wide bevel is in full contact with the stone and sharpen with even pressure over the entire thing, the wide bevel should just move up the knife, staying at a constant angle. So, assuming the grind is basically constant width outside the bevel, the shinogi will move up. Here's a before/after pic of a chisel sharpened in this manner.

    thinning.jpg
     
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  13. Dec 2, 2019 #13

    labor of love

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    Okay you got me. :) I did word that incorrectly.

    But if thinning evenly on the entire wide bevel acts to maintain geometry that wouldn’t be enough after removing steel from the edge correct?
    At that point it’s not about maintaining an altered profile, it’s about reestablishing a former geometry.
    You’d have to over compensate in the shinogi area for the steel lost at the edge.
     
    Last edited: Dec 2, 2019
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  14. Dec 3, 2019 #14

    ian

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    Totally. The way I was interpreting @Viggetorr’s OP, though, I think he was just suggesting to thin more in the middle of the knife than on the extremities, without ever screwing with the edge on its own. That would work (I think), although maybe would be hard to control. And of course it’d be a lot of work.
     
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  15. Dec 3, 2019 #15

    kayman67

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    I would draw a new profile and work my way towards that. With proper plates, should be a bit easier. I did similar stuff, but not on Takeda. Don't eyeball-it.
     
  16. Dec 3, 2019 #16

    Benuser

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    Excuse my ignorance, but what is a low bevel?
     
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  17. Dec 3, 2019 #17

    ian

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    I assume he meant the wide bevel is not very wide.
     
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  18. Dec 3, 2019 #18

    Viggetorr

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    Exactly. It doesn't seem like it would be too hard to me, but maybe that's because I've never tried anything similar before! :D I find it very easy to sharpen this way, but of course this would mean remove a lot more metal than a regular sharpening session. I'd imagine the biggest challenge would be getting a nice flat edge throughtout the middle of the knife?
     
  19. Dec 3, 2019 #19

    ian

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    Yea, but I’d question whether you really want a truly flat edge. You probably want just a less aggressive curve. If your edge is perfectly flat, it may feel weird on the board. And if your cutting board is not *perfectly* flat, a flat edge won’t even contact the board where you’re cutting. Much better to have a gentler curve.
     
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  20. Dec 3, 2019 #20

    Viggetorr

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    That is true, I guess that's what I actually want. My concern, then, would be maintaining a perfect curve without accidentally creating "deeper spots" along the edge that won't come into contact with the board whereas the edges on both sides does.
     
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