Grinding Jigs - getting that crispy Shinogi at the tip

Discussion in 'Shop Talk' started by erezj, Dec 6, 2018.

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  1. Dec 6, 2018 #1

    erezj

    erezj

    erezj

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    I'm a small time knife enthusiast, my particular favorite is Wrought Iron San Mai with strong distal taper and crisp Chisel grind...but after building about 7 knives I still haven't been able to get that crisp shinogi all the way to the tip.

    no problem with 70% of the knife, just the tip when it becomes so thin and sweeps up.

    Tried using a basic wooden block jig with two screws to fix the angle, tried free hand...got reasonable success, but not where I want it to be

    appreciate any advice
     
  2. Dec 7, 2018 #2

    Kippington

    Kippington

    Kippington

    A small green parrot Hobbyist Craftsman

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    Have you considered a slightly concave grind (i.e. large radius wheel)? They really seem to help for the bulk of the work, then you can change it to a flat quite easily by hand once the bevel is almost complete.

    There's some more info here about distal taper and its effect on the shinogi line:
    https://www.kitchenknifeforums.com/threads/commission-wip.34734/

    [​IMG]
     
  3. Dec 7, 2018 #3

    erezj

    erezj

    erezj

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    Kip, had a blast reading the thread you shared!

    And, ya man, your knives are amazing + your knowledge sharing is, for me, what this community is all about !

    However...if was quite challenging for me to reach a conclusion...

    so followup question:
     
  4. Dec 7, 2018 #4

    erezj

    erezj

    erezj

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    [​IMG]

    If I analyze the diagram Kip shared above, my conclusion is that the only way to make a Shinogi parallel to the edge in a strongly distal taper knife, is to do it free hand and slowly raise the angle the closer I get to the tip
     
  5. Dec 7, 2018 #5

    Kippington

    Kippington

    Kippington

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    I'm glad you enjoyed it, but if you read further you'll see there's another way. It involves the flats being not quite flat/parallel.
     
    milkbaby likes this.
  6. Dec 12, 2018 #6

    Dan P.

    Dan P.

    Dan P.

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    I'm not the shinogi master, the shinogasaurus, I'd like to be, but leaving the tip a little chunkier can help keep the grind line from being either too thin or getting out of control.
     
  7. Dec 19, 2018 #7

    comet_sharp

    comet_sharp

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    You're most likely subconsciously twisting your wrist at the end of your passes. Just practice more and don't get discouraged.
    -Trey
     
  8. Dec 19, 2018 #8

    erezj

    erezj

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    Thanks for the assistance, just finished a new blade yesterday, got the Shinogi quite well, my temp solution, elbow grease.

    It took forever, but got the results I was looking for, now I just need to learn how to do it on the grinder and save me lots of blisters, raw fingers and a **** load of time.
     
  9. Dec 27, 2018 #9

    merlijny2k

    merlijny2k

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    Oddly I don't find it harder to get a certain shape on the grinder than on a stone. It is just so damn hard not to overheat the tip and or the heel as the grind gets thinner. Just yesterday I got another tip scorched black in about two seconds. With my lever of patience I really should have something watercooled. I find it really odd that so many of the best makers have machines without cooling while cooled ones do exist.

    I haven't worked with laminated steel yet, but I have tried to get even widebevels (with varying levels of success). Some of the things I find promoting success:

    1. Make sure the handle or transition to the handle doesn't interfere. Best solution so far is to have a temprary handle for grinding taht stays much futher down the tang compared to the final one. This solves irregularity near the heel which you don't have.

    2. Have the steel somewhat thicker than the intended finish. My most successfull approach (full freehand) goes somehing like this: first grind taper to about 80% of intended, then grind bevel. While grinding the bevel I switch back to taper everytime I cross the intended line, pushing it back to where it should get. This requires some extra thickness to expend, hence the 80%taper first. I grind the bevels perpendicular to the knife and the taper along the length of it. This gives perpendicular scratch patterns which helps with seeing what you are doing. I finish with grinding some taper. Depending how even the bevels are I get a reasonably even blade road. I don't get it perfect or anywhere near it, This is just my most successfull approach after six tries.

    3. For grinding the tip you can't have the blade perpendicular to the belt, you really have to follow the curve of the edge, always keeping the edge perpendicular to the belt. I see no way to avoid things getting wonky if you don't. From my experience and your description it might be the reason for your troubles.

    One thing I am still very conflicted about is where in the process to do the hardening. My blades hardened early I always end up visibly overheating some spot at some point. That is not even counting overheating that does not result in a burnmark. Blades hardened late in the process have all warped on me but I have had some success getting them straightened.
     
  10. Dec 27, 2018 #10

    milkbaby

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    Digression from original subject: Some makers will heat treat a profiled but unground knife and do all grinding post-HT. This can help avoid warping which is more likely when the blade isn't perfectly symmetrical, i.e. leave it unground and it won't have grind induced asymmetry so less likely to warp. Also an unground knife can easily be squished between aluminum quench plates at heat treat which also keeps it straight.

    When grinding post-HT one thing to be careful about is managing the temperature of your grinder platen. I only have a 1x30 belt grinder and the platen is very inefficient in dumping heat. I do one grinding pass then dunk the blade in water to cool it, and spray the platen liberally with water to cool it.
     
  11. Dec 27, 2018 #11

    merlijny2k

    merlijny2k

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    Yeah I got a bit carried away typing I guess. Part of the problem is I am still grinding with thick gloves. Still reluctant to go bare. That would solve some of the overheating probably.
     
  12. Dec 27, 2018 #12

    erezj

    erezj

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    Bare hands will help a lot avoiding burning the tips! but it really f****s the fingers in so many ways...some of us really like the 'battle' marks :)

    thanks for the process description above, I guess thats about what I usually do, grinding that last 20% of the taper at the end helps clean all the places where I damage the shinogi line before, unfortunately, it also reduces the height of the shinogi at the tip, when I try to fix that...mistakes happen :)

    guess I just need practice practice practice
     

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