Working the hollow out of a Moritaka

Discussion in 'The Kitchen Knife' started by DisconnectedAG, Jun 14, 2019.

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  1. Jun 14, 2019 #1

    DisconnectedAG

    DisconnectedAG

    DisconnectedAG

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    Hi everyone,

    Looking for advice from anyone who has Moritaka knives and has done the work to get the hollow grind out of the apex.

    I have the AS guyto and the B2 nakiri. Not my favourite knives anymore, but they were part of my knife journey. One thing I've discovered is that both have a fairly pronounced hollow in the grind below the shinogi line.

    I have a Shapton Pro 320, so can probably get rid of the hollow pretty easily just by going about it in the same way as if I was thinning, but I am concerned that due to the hollow, I'll have to remove metal to a point where the lowest end of the hollow basically becomes the new base for the shinogi, if that makes sense (because I need it to be flat, so to speak).

    Have any community members done this? Will this weaken the blade significantly (as you essentially get a much thinner wedge), and anything I should consider? I'm not terrified of ruining the knives, as it's good practice, but obviously don't want to harm them if I can avoid it.
     
  2. Jun 14, 2019 #2

    lemeneid

    lemeneid

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    Why do you need to have flat bevels?

    I would discourage thinning out hollow ground knives. If you do so, you definitely thin out the knife a lot more and raise the shoulders significantly, and it might lead to more wedging, worse food release and most of all, loss of cutting ability.
     
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  3. Jun 14, 2019 #3

    DisconnectedAG

    DisconnectedAG

    DisconnectedAG

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    Basically, I wanted to use at least one of them to practice my polishing skills. I'm thinking of taking the dive into a jnat and since the Moritaka is iron clad it gives a good oppotunity to play around with the finish. Also, If ind that the hollow discolours/patinas quite annoyingly. I'm not one of those guys who removes patina all the time, but since the deep end never touches anything it gets much darker than anything else.
     
  4. Jun 14, 2019 #4

    MrHiggins

    MrHiggins

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    If you want to get the hollow out, you can use course (140 grit) sandpaper taped to a flat, hard surface. I find that this technique removes a lot of material very quickly. I then move up to 220, then 400 paper before I take it to any stones.

    I would keep the pressure over the hollow, not at the edge or up near the shinogi line. You will probably go through a few full sheets of course sandpaper before you get close to flat. Also, check often that you're keeping an even shinogi line. Good luck!
     
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  5. Jun 14, 2019 #5

    gman

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    when i've flattened out hollow or S grinds i've found it helpful to alternate course and fine stones. the reason being it can be difficult with all the slurry and scratches to gauge progress on the course stone, and you could easily take it too far. by alternating with a polishing stone you get a much clearer picture of your progress, both in terms of how much hollow is left, and in keeping both the profile and shinogi straight.
     
  6. Jun 14, 2019 #6

    M1k3

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    I think OP is talking about removing an overgrind.
     
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  7. Jun 14, 2019 #7

    DisconnectedAG

    DisconnectedAG

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    I think so, but may be wrong. It's not sold or mentioned as a hollow grind, but it may be intentional, it's hard to know.
     
  8. Jun 14, 2019 #8

    GorillaGrunt

    GorillaGrunt

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    The one Moritaka I had didn’t have an overgrind but did have wheel-ground slightly hollow wide bevels. It was a good learning practice for thinning and working with blade geometry to flatten them and fool around with a bit of polishing. I just used coarse stones and it was pretty easy to see when I hadn’t gone far enough and when I had; the steel is good and it won’t become fragile from thinning. It should be microbeveled as opposed to using it zero ground though.
     
  9. Jun 15, 2019 #9

    lemeneid

    lemeneid

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    Take a credit card and run it perpendicular through the bevel along the whole edge of the knife, if you see light throughout, it’s hollow ground. You can use this method to check overgrinds too.

    Additionally since you’re a polishing and jnat beginner, I still highly discourage thinning hollow ground knives for educational purposes unless you’re okay with irreversible damage. Otherwise find a cheap convex grind and learn from that.
     
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  10. Jun 15, 2019 #10

    DisconnectedAG

    DisconnectedAG

    DisconnectedAG

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    Thanks for the credit card trick. Will try this. Re damaging the knife, I take your point and I'm aware of this. Will probably practice on the Nakiri, asimnor bothered if that gets damaged, and leave the gyuto alone for now, as it may have some resell value.
     
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  11. Jun 23, 2019 #11

    DisconnectedAG

    DisconnectedAG

    DisconnectedAG

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    For those who are still following this thread, I did the credit card test on both the Moritaka nakiri and gyuto. They are clearly not designed as hollow grind, they're just ground super lazily with low spots throughout that need to be ground out. I like the shape of the guyto with the very long flat spot at the back though, it's very different from anything else I have.
     
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