Commission WIP

Discussion in 'Handiwork Display' started by Kippington, Nov 7, 2017.

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  1. Nov 7, 2017 #1

    Kippington

    Kippington

    Kippington

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    I'm working on a new knife and found something that you guys might find interesting!

    If you have a strong distal taper on a knife, like this:

    [​IMG]

    Grinding the primary bevel at a consistent angle makes the shinogi travel in a funky line as the spine gets thinner and the bevel slowly runs out of space to go:

    [​IMG]

    Just something cool I thought I'd share before I blend it all together and this little detail gets lost :)
     
  2. Nov 7, 2017 #2

    Nemo

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    This makes sense but it is cool to see it. Thanks for showing it.
     
  3. Nov 7, 2017 #3

    Kippington

    Kippington

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    Thanks Nemo
    HOLY CRAP :bigeek:
    I recall an image from this old thread... suddenly it makes sense!

    [​IMG]

    Oh man, this is so much fun! :lol2:
     
  4. Nov 7, 2017 #4

    RDalman

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    It can also be that the edge is not very straight. A "good" grind will show this more than one with chunky edge also. Not saying that is the case here, just that it can show like that :)
     
  5. Nov 7, 2017 #5

    Kippington

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    I was quite sure it was straight, and a good grind too... but now you're making me double-check it! :razz:

    Yeah it looks good, but the straightness along the edge is damn near impossible to catch in a photograph. Hell, it was hard enough to get a good picture of the distal taper!

    At the very least I'm hoping these images demonstrate the primary bevel getting smaller as it moves further away from heel and into an ever thinner cross-section. Even as it moves up the belly of the knife towards the tip, the bevel is always shrinking in width. I'm looking forward to finding out how well this cuts :laugh:
     
  6. Nov 8, 2017 #6

    ashy2classy

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    Very cool to see the grind picture...knife looks great! Thanks for sharing.
     
  7. Nov 8, 2017 #7

    jessf

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    I think this is pretty standard geometry when you cut the bevel first, then apply distal taper. Had you applied the taper first then cut the bevel there would be less of a need to go back and fix the bevel. The angles close up as you get closer to the tip so there’s a lot of free hand blending needed.

    I believe the photo of the japanese knife is the result of a warped blade that wasn’t sufficiently straightened post heat treat or flattened on the stones before the edge was applied.
     
  8. Nov 8, 2017 #8

    Kippington

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    Can you explain what you mean in more detail?

    As I understand it, if you do a good job on both the distal taper and keeping a consistent bevel angle, you should end up with the same end product regardless of whichever one you did first.

    [​IMG]

    The picture in the first post is very much like these diagrams, only there is an added sweep of the belly which makes it unappealing to the eye. It's a bit of a shame that it looks bad because there's nothing on the bevel to 'fix' as far as I can tell.

    Also FWIW I actually did the taper before the bevel.

    I hope this makes sense. It does in my head. :O
     
  9. Nov 8, 2017 #9

    merlijny2k

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    I always thought the idea was that the lesser height of the bevel should more or less correspond with the lesser height of the entire knife. If you start with a higher bevel it takes longer before you run out. On another note, if I look st how my Kamo is ground which is widebevel like you are making, he takes bevel height as the constant, not bevel angle. Gives a super thin tip but that is definitely the approach I want to take once my grinder arrives.
     
  10. Nov 8, 2017 #10

    JMJones

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    Are you doing the grind with a jig?
     
  11. Nov 8, 2017 #11

    milkbaby

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    I think what jess says about the angle closing up, what m2k says about keeping the blade road height the same, and what JMJ asks about using a jig are probably right. If you use a sled jig to grind the bevel after grinding in the distal taper, it won't account for how the flats narrows as you go from heel to tip. Freehand automatically takes into account the distal taper. Or you can use something like Fred Rowe's bubble jig which is only a visual indicator that your freehand angle is staying constant.

    When the width produced by the angle of the bevel grind exceeds that of the distal taper at the spine, then the shinogi would have moved up to the spine which is what you typically see.
     
  12. Nov 8, 2017 #12

    jessf

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    You’re right. Not mater how you start the end product can be the same, so my original comment wasn’t accurate. I freehand my bevels and distal taper and blend all at once. So i’m really touting the time saving merrits of freehand grinding. But you didn’t really ask for that kind of advice so i’ll shut up for now.
     
  13. Nov 9, 2017 #13

    Kippington

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    Wow, what an eye opening response from other knife makers. In my defense, this is still a work in progress!

    Thanks for all your advice on grinding wide-bevels - I might try creating one in the near future to see if I can tackle this very topic.
    This particular knife was never designed to be wide-bevel, it only looks a bit like one after the distal-taper was first set, then the initial bevel had reached the center on both sides.

    Say what you will... I still find the idea behind this shape to be a thing of beauty:

    [​IMG]

    Don't worry, I don't believe it leads anywhere dramatically improved, different or super useful. I wont chase it down a rabbit-hole - I simply saw it mid-way through making this knife and thought... nice. :)

    By the way, if any of you guys possess the skill to add a well defined sweeping wide-bevel onto both sides of this taper, I'd happily admit you are a way better knife-maker then I am... that would take some next level wizardry! :laugh:

    [​IMG]
     
  14. Nov 9, 2017 #14

    milkbaby

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    That diagram is for a rectangular chisel and is not applicable to your knife with a curving edge. If you're using a sled jig to keep the angle the same, then as the edge moves away from the line of the heel, you're actually grinding a less acute bevel angle. You want the angle consistent to the edge, not the line running from the heel parallel to the spine.

    I assume you didn't keep the pictured grind or did you? That last picture with the coin seems to look good?
     
  15. Nov 9, 2017 #15

    milkbaby

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    Here is what my thought process comes to:

    [​IMG]

    And I am totally open to being wrong, and if so hope somebody can explain why.
     
  16. Nov 9, 2017 #16

    Mute-on

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    This is how I envisage the issue, too. Well conceived, milkbaby.

    If this goes much further, though, my head will explode ;)
     
  17. Nov 9, 2017 #17

    Kippington

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    But oh no! I totally disagree!
    This is a sweet discussion though :laugh:

    I am torn as to whether to go off your diagram, or to draw my own crudely designed picture. I'll try using yours - tell me if I am making sense or if I am maybe missing something obvious.

    [​IMG]

    In this picture, the distal taper causes Green XSection to be the widest and at the same time has the shortest profile (Green Profile).

    If you move towards the tip of the knife in your image, Red XSection gets shorter, at the same time the Red Profile gets longer... and it gets worse at the Blue line! The bottom triangles are an approximation of what happens to the bevels (ignoring the flats I guess)

    There's no way of sticking to one constant bevel angle when you include a taper. If you consider the White Profile line (right angle to the edge), this distance is supposed to stay the same no matter where you are along the wide bevel. This is a good way of sticking to one bevel angle, however this will only work if you do not have a taper.

    Well that's how I see it anyway, please feel free to tell me how I'm wrong or if none of this makes sense :laugh:

    BTW that coin picture above, that was what the taper looked like before grinding any bevels.
     
  18. Nov 9, 2017 #18

    milkbaby

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    Kippington, I agree with your analysis of my diagram: my drawing is wrong. The way is drawn actually agrees with what your initial picture showed with the grind lines getting shorter as you get to the tip.

    We should actually cross section the blade orthogonal (perpendicular) to the edge as shown by your white line; that's actually the bevel height we all consider not the straight up and down lines we drew. The bevel grind angle CAN remain the same as long as your distal taper doesn't thin out (before the blue line) any smaller than width of the shinogi at point GP. I think on this point we'll agree.

    If your distal taper goes thinner than the shinogi at GP before you hit the blue line, then your grind angle has to narrow to maintain the same height. This concurs with jessf in his first comment.

    I think this is an excellent discussion! Y'all let me know if there's something else I didn't consider, but I think this post finally hits the nail on the head. :)
     
  19. Nov 9, 2017 #19

    milkbaby

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    As soon as I replied I think I'm wrong again. LOL

    Edited: if your distal tapered flats are consistent width from the spine to the shinogi or grind line, then the grind angle has to narrow to maintain the same grind height or you get what you showed in your grind pic.

    The only way to maintain the grind height at the same edge angle is if the "flats" are actually angled from the spine towards the edge. I bet this is the case in Japanese forged wide bevels, i.e. they're not forged flat but thinner as you go towards the edge from the spine. Then the grind puts on the blade road that is a consistent height. This would be a full height compound grind in stock removal. The distal taper would still have to not run down thinner than the at the shinogi at the blue line to be able to maintain the angle and grind height.
     
  20. Nov 9, 2017 #20

    RDalman

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    Bingo! But on the grinder you're not limited to loosing forging heat in a second when getting really thin. Nothing stopping anyone from doing both aye.
     
  21. Nov 10, 2017 #21

    Kippington

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    Thanks for posting that image milkbaby, had you not drawn it, this thread could've gone very differently! It was starting to feel a little one sided against me, and I could've sworn I had the right idea about what was going on (pretty sure some of the same traits are showing up in the Kato picture), but I wasn't going to start trying to explain stuff out of the blue! :laugh:

    I'm looking forward to trying to make a dedicated wide-bevel in the near future. I will have to think about what you said about the flats not being parallel, cant quite wrap my head around it, but it definitely shows up in this picture at the Hira:

    [​IMG]

    But first I need to complete this current WIP.

    Quick! Somebody check on Mute-on!

    [​IMG]
     
  22. Nov 10, 2017 #22

    Marek07

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    OK... that's one diagram too many! I'm now totally lost. :dazed:
    Once you get your head around all this Kipp, perhaps you could explain it to a much more confused brain (mine) in short sentences & simple diagrams. Might be easier in person - with knife, grinder and jig all in view.
    :wink:
     
  23. Nov 10, 2017 #23

    Kippington

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    Sure thing Marek! :biggrin:

    [​IMG]
     
  24. Nov 10, 2017 #24

    milkbaby

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    Yeah that drawing on the right that shows the hira angled in is what I was saying in words in my last post. It is possible to calculate all the angles you want to grind but in practice it's easier to just go by eye especially if freehand grinding. And forging is different as you only have a picture in your mind's eye where the centerplane of the blade is as well as the various angles which are a bit wobbly depending on how good you are with the hammer forging in the geometry evenly.

    In the end as Robin said on an my Instagram post of that diagram, performance is what matters no matter how you arrive at it.
     
  25. Nov 10, 2017 #25

    Mute-on

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    Too late ...

    What a mess! ;)
     
  26. Nov 10, 2017 #26

    jessf

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    I recall now that I forge in the taper then freehand grind the bevel. I haven't made a blade in a while so it all starts to fall out of my head.
     
  27. Nov 11, 2017 #27

    Kippington

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    Well I've finished the grind and have attached a makeshift handle on it - Time to give this knife a test run!

    I'm used to using 'lasers' over 'workhorses' so I was a little clunky at the start of the video, but I got into the rhythm after the first few cuts. She's a different kind of beast, I can tell you that much!



    Labor of love asked for a thicker grind on this knife, so I took a lot of inspiration off the Kato thread that was mentioned earlier. I'm very pleased with how this has turned out!
    This is the pre-polish check up with Labor, making sure its all good with him before I spend hours making it pretty. Figured I may as well post it in this existing WIP thread. :)

    This thing is heavy! 236g with a light handle attached. As I understand it, this is actually lighter than a Kato 240mm, even though this knife is both taller and longer.
    I have it balancing on a pencil to show center of mass.

    [​IMG]

    [​IMG]

    [​IMG]

    The blue reflection gives an idea of how the previous 'wide bevel' grind is now a blended concave grind. Spine is 4.3mm thick above the heel, quite beefy and (I believe) the same as a Kato 240mm. The taper hasn't changed from the first image on page one.

    Taking a picture to show straightness of the cutting-edge is next to impossible...

    [​IMG]

    I'm not looking forward to polishing, but it has to be done... I might see if I can bring out the hamon if it doesn't take too much effort - although I hear its a pain in the ass to do. :scared4:
     
  28. Nov 11, 2017 #28

    labor of love

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    Oh man, I’m gonna have a real good time with this beast.
     
  29. Nov 11, 2017 #29

    Kippington

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    Haha sweet! I'll get to polishing it tomorrow. :biggrin:
     
  30. Nov 11, 2017 #30

    Marek07

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    Wow! I'm holding the passaround which is beast enough for me. This one needs to come with a health warning!.
     

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