Grinding wide bevels - how to?

Discussion in 'Shop Talk' started by Matus, Jun 27, 2019.

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  1. Jun 27, 2019 #1
    I would like to try to make some knives with a wide bevel grind. I started to work on one and quickly realised, that I need to proceed differently that to what I am normally doing (gentle convex grind) where I start grinding at the edge and slowly move towards the spine and at some point start to work on the distal taper and then keep slowly correcting it peu-a-peu until I like what I have .

    The result I would like to achieve is:
    • distal taper (obviously)
    • grind tapering from shinogi to the spine
    • even shinogi line
    • more-less flat wide bevel grind (the hamaguri would be only made in the finishing steps of grinding or even on stones after that).
    What I do not know is how to start or proceed (technique, tools, etc.). I did not find much of usable input online so far, so I decided to ask for your help.

    I would appreciate your input as how to start. I am fully aware that neither my first nor 5th knife will be perfect, but that is part of the learning curve.

    Thanks in advance
     
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  2. Jun 28, 2019 #2

    refcast

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    If I were to do it, but I don't have the tools:

    If it is a san-mai knife, the core needs to be exposed on both sides evenly as a first step. Monosteel doesn't need this consideration. I would also assume you're not doing single bevel.

    First grind for the distal taper your want, on the blade face. Consider whether you want the face to be flat, slightly hollow for food release, tapered to be thicker at the spine for more meat, or tapered to be thicker a bit at the shoulders for more food release. There could be convex faces, but I've never seen one.

    I would draw or mark the shinogi line you would like. Higher = thinner and more room for convexing, lower = better food release and easier to make. Raquin, Heiji are lower. Konosuke, Halcyon forge are higher.

    Grind from shinogi line down to the edge. If you're using belts, there might be some give in the belts, which would produce a convexing, which isn't necessarily bad. So either have more tension or stiffer backing, or finish on stones / plates. Feel with your fingers as you thin and produce the bevel. Try to switch sides evenly as you go to control warping.

    If you give the knife a bunch of distal taper, the wide bevel will be really thin at the tip, so consider if you want that and microbevel it, or have a thicker spine there and less taper.

    I've seen videos of draw-knives and large waterwheels used to make the wide bevel.
     
  3. Jun 28, 2019 #3

    milkbaby

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    Are you talking about stock removal only? I say just do it the same as forged: forge/grind the distal taper first then grind the bevel. To get an even distance between the edge and shinogi line, don't use a set angle jig but instead your eyes and inspect after every grinder pass to see what you're actually doing.

    If you're also doing a compound grind, where there is a shallow angle from spine to shinogi then a steeper angle for the wide bevel, I would set the angle above the shinogi by doing a full flat grind then grind the wide bevel. In fact, this style is probably the next knife that I plan to make.

    You may be overthinking it. Maybe just changing your procedure to doing the distal taper first then everything will fall into place for you?
     
  4. Jun 28, 2019 #4
    I apologize - I indeed meant only stock removal of double bevel knives.

    That is exactly what I would like to achieve in terms of grind. What you propose definitely makes sense.

    What I am also wondering whether thus would be easier to grind on a platen or using a large grinding wheel on a belt grinder (I do not have such a wheel yet though)
     
  5. Jun 29, 2019 #5

    RDalman

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    I think wheel and practice. You "just" need to get able to grind just the spot at all times. If you want the bevels flat I'd say still you're best off starting on wheel and then flattening it down. I think it's too difficult to do on a flat platen because grinding on belt grinder platen always makes convex.
     
  6. Jun 29, 2019 #6

    Kippington

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    I've worked out a way to do it with a jig, but I haven't tested it properly. It involves a large radius wheel/platen. I will try it soon, as someone ordered a wide-bevel from me.

    Working it out was basically just solving the problem of the changing angle of the wide bevel as it travels down the knife, shown in this old diagram:
    [​IMG]

    I'm too lazy to draw any new diagrams at the moment, but it seems simpler than I had previously thought.
     
  7. Jun 29, 2019 #7

    RDalman

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    I have jig allergy, maybe because I suck at dancing.
     
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  8. Jun 29, 2019 #8

    RDalman

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    Can a radius platen ever run a belt cool enough for zero-grinding on belt?
     
  9. Jun 29, 2019 #9

    Kippington

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    Yep! :D
    At high speeds too.
     
  10. Jun 29, 2019 #10
    Thank you guys for your advice.

    Kippington - that is close to what I want to achieve.

    Robin - I have seen at least one radius platen that was water cooled from behind. But I guess one would need water being sprayed on the belt to keep it cool enough.

    EDIT: Kippington - I only saw your last reply now. I am finding that even on a flat platen one really needs to be careful especially with finer belts. I would naively guess that on a radius platen this would get worse. I would love to hear more of your experience on radius platens in general
     
  11. Jun 29, 2019 #11

    RDalman

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    Ribboned rubber wheel, whole other level of cool and speed.
     
  12. Jun 29, 2019 #12
    The will be my first bigger purchase once we manage to find a house, buy it and move in it and still have money left for other stuff than food :D
     
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  13. Jun 29, 2019 #13

    Kippington

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    Mine is ghetto. It's just a bar of steel with a bend in it, placed between the flat platen and the belt. In such a way it won't fly out obviously.

    Back on topic, I'll try to explain the idea. It's 2am here so I hope it works.
    Assuming the flat platen is static, there is only one way to change the angle of a knife grind - by raising or lowering the spine.
    On a radius platen (or a big wheel) there is a second way to change the angle. If you keep the knife angle the same but move it to contact higher or lower parts of the radius, the angle changes.

    So my idea is to grind the knife at the normal angle at the heel, keeping the spine at the same angle the whole time, but slowly moving the whole knife up the radius as I grind towards the tip, which in turn subtly changes the angle of the bevel. It ends up as a smooth transition of angle from a thicker grind at the heel to a thinner one at the tip.

    Does this make sense? I hope so.
    It works on tests but I have yet to make a full knife from it.
     
  14. Jun 29, 2019 #14

    Carl Kotte

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    I am ready to pull the trigger on a wide bevel! (I think)
     
  15. Jun 29, 2019 #15

    RDalman

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    Just watch out so you don't mess up the finish and mess with the resale value. And load your gun with glass bead shells.
     
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  16. Jun 29, 2019 #16

    Carl Kotte

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    Yes yes, I will do all that...
     
  17. Jun 29, 2019 #17

    Carl Kotte

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    I.e. mess everything up and end with a 0$ knife
     
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  18. Jun 29, 2019 #18

    playero

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    If you mess up and it’s your knife at least in my case I still use them and try other things with them. Most of them time I have two of the same knife.
     
  19. Jul 2, 2019 #19

    erezj

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    Matus,

    Had put a lot of effort into the topic a few month back...the conclusion for me was, learn how to do it freehand, its painful, but worth it at the end.
    Ill try to explain my reasons:
    1. Each bevel is different, the width, distal taper, outline, length all affect the rate the angle of the bevel changes as go towards the tip, or as the width becomes more and more narrow.
    2. I tried working with Jigs, I found that its not 'dumb proof' , you cant get around it, you have to learn to feel the bevel on the grinding machine.
    3. Once you do master the technic, you find it helps you in any grinding job, your fingers just become more sensitive.

    As for the two most important 'realizations' for me free handing:
    1. Once I really understood the gradual change in the angle of the bevel as the taper becomes thinner, helped me understand the general motion, basically, the closer to the tip, reduce angle and lift knife. (Thanks Kippington for the great threads)
    2. I always leave the flat above the shinogi a bit too thick, this way, after I finish the bevels (and I always F*** it up) once grinding the flats, it cleans the Shinogi and becomes 'crisp'

    however, would love to see Kip's jig in action
     
  20. Jul 2, 2019 #20
    @erezj, thank you. I definitely plan to do it free hand (I am not patient enough to invest many hours in complicated jigs anyhow :p). I would like to ask whether you grind on a wheel or a platen and how do you get the best consistency. I am so far grinding on a platen that is in standard (vertical) position and keep the blade perpendicular to the platen edge up. I do plan to get a wheel, but that may be happening only next year for technical reasons.
     
  21. Jul 2, 2019 #21

    erezj

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    I use a self build 2 inch belt grinder, and the girding is done against a horizontal flat plate.

    As for how to reach consistency, a few parameters:
    1. Practice, practice, practice. I would recommend getting a cheap 5mm steel plate, cut out a knife shape and grind wide bevels, then try on a 4mm, then on a 3mm....the thinner the knife, the bigger the challenge.
    2. Posture ! you want the whole body to be relaxed, the less muscle tension, the more feeling to have, how do you learn Posture...practice internal martial arts or ...practice until your body relax.
    3. Visual feedback, keep your eyes on the edge touching the belt, it will hep you both to keep the blade parallel, and to focus
    4. Light touch, don't push your knife into the belt, every thing has to be done gently and gracefully, no sudden moments.
    5. Pay special attention to the initial contact and to the release, that is were you usually make the biggest mistakes.
    6. watch Youtubes, I would recommend Walter Sorrells and actually learned alot from Alec Steel channel, grinding perfect bevels on long swards.
    7. move as little as possible - lock your legs, lock your arms, try to have a flowing motion from the hip.
    8. Dont forget the tip, the angle is usually smaller (if you want the shinogi to rise at the tip parallel to the edge) due to the thinning of the knife (distal taper), so when you reach the tip, slightly reduce the angle and bring the handle closer to the body(lift).

    those are my 7 cents

    but please remember, i am a novice myself, and still trying to implement my own advice with mix successes, so feebacks from you pro's will be most welcome.
    Evaluate each 'Advice' with your own common sense.

     
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  22. Jul 2, 2019 #22

    Dave Martell

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    I'm going to be the oddball here because of how my grinder is set up so how I do it is based on this factor.

    My grinder is laying down so that the platen is horizontal with the bench, much like a waterstone is when sharpening. So I work a wide bevel by grinding it just like I sharpen a wide bevel on a stone, going from corner to corner. This gives a wide contact area between the platen and knife where wobble is greatly reduced.

    Doing it this way also helps to grind the wide bevel evenly through a twist and raise action (again) similar to what you do while sharpening on stones.

    I do have to sometimes go across (90 degs to) the platen to fix/address specific areas but only when needed.

    *Always grind in the distal taper first before the bevels.
     
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  23. Jul 3, 2019 #23

    osakajoe

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    Just lower your angle. This of course is after you invest in an large water wheel as seen in one of Jon’s old videos.


    Very simple lol
    You will need enough to buy a small car though.
     
  24. Aug 12, 2019 #24

    BT11

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    I've mucked around making a couple of wide bevels. Mark your centre line on the edge, scribe in where you want your bevel to finish. And slow and steady with freehand grinding. Slowing the belt speed down when you start getting thin at the edge, or want to work on a particular area helps not cook it. Once I'm about 90% there I'll go to my disc grinder and flatten and smooth the bevel out until its near zero
     
  25. Aug 19, 2019 #25

    Kippington

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    My jig seems to work, but there are all kinds of little details I'd need to explain to be able to tell you how it works in full. Just know that my explanation a few posts above has practical value.
    This blade is 240x52mm (it will get smaller), has distal taper, and is beveled on both sides:
    [​IMG]
    [​IMG]
     
    Last edited: Aug 19, 2019
  26. Aug 19, 2019 #26
    That looks pretty impressive
     
  27. Aug 19, 2019 #27
    This is what I managed to make on the grinder. I plan to take it to stones/sandpaper/diamonds from here (I will be trying different approaches and see what works best).

    11EAD21F-891F-4763-817B-8B792A296D35.jpeg
     
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  28. Aug 19, 2019 #28

    Kippington

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    Very nice! Did you manage to do both sides with distal taper?
     
  29. Aug 19, 2019 #29
    Yes (more less). I first ground the distal taper and then continued with the wide bevel. I may go back to grinder and finer belt, because 1.2442 at 63 hrc is no fun on stones when it comes grind adjustments.
     
  30. Aug 19, 2019 #30

    Nemo

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    Post deleted as my question had already been answered earlier in the thread.
     
    Last edited: Aug 19, 2019

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