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Thread: Asymmetry – The REAL DEAL

  1. #31
    I thought of another example that might help clear this matter up some.

    Let's this time use a honesuki (a double beveled 90/10 ground knife) as our test mule. We'll use a right handed version here for our discussion.

    So this is a knife that's a bit thicker than a gyuto is and much more asymmetrically ground.

    Here's a picture of the right side of the knife....




    Here's a picture of the left side of the knife....




    You should note that the edge bevel on the right side of the knife is significantly taller in height than the bevel is on the left side, in fact the left side edge bevel is almost difficult to see at all.

    This is a good example of how you can not use the same angle when sharpening both sides of the knife and that's true for both free handing and using a guided device.

    If you're free handing the spine will have to be further away from the stone on the right side of the knife then when compared with the left side but only by a small amount. This is to adjust for the thicker blade.

    If using a guided device (like the Edge Pro) it is easy to see (in use) how you must change the angle of the stone arm. What happens is say we choose the left side (the side with the very small bevel) to sharpen first. We lay the knife down onto the flat table and then adjust the stone arm to hit this edge bevel correctly, making about a 1-2mm bevel at the very cutting edge. When we flip the knife over to the right side (the side with the large bevel) we immediately see that the stone is hitting above the edge bevel on the right side. Why? Because the knife is nearly flat on one side and has a large wide bevel on the other side - it's asymmetrical.



    Now let's take a single bevel (a 100/0 ground) knife like a yangiba and sharpen this both using freehand and a guided device and what do we have happen? We see the very same things as we do with the honesuki (90/10) knife except the issue of having to use different angles is even greater enhanced for us to note and have to deal with.

    Is there anyone who thinks that you can use the same angle on an Edge Pro (or even freehanding) for both sides of a yanagiba (by using the grind more on one side than the other method or the counting strokes method) and have it come out OK? I seriously doubt that I'll find someone who can show me this to be the case. Why? Because I know that I have to sharpen at least a 15deg bevel angle on the right side and then switch to 0 deg the left side. Why? because the knife is asymmetrical - FACT!

    The very same principle/practice is true for all Japanese knives because they are all asymmetric, the amount of change that we make (or not) is dependent mostly on the amount of asymmetry of a particular style of blade as well as the blade's thickness. We can, but should not, ignore these simple facts if we want to properly sharpen our Japanese knives.

  2. #32
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    Thank you! This example just helped my head a lot. Makes perfect sense that I would have to adjust the arm's angle on the Edge Pro every time I flip the blade to accommodate asymmetry. It is starting to really come together for me now.

  3. #33
    I think the best way of explaining why some people don't like guided devices for sharpening around these forums is pretty simple. A guided device does nothing more other than provide a sharp edge. If you want your knife to cut great than you definitely need to free hand IMO. So if all you care about is slicing paper with no effort take a guided device, if you care about cutting all sorts off stuff with ease then go the hard way and learn how to free hand.

    As Dave mentioned there are no absolutes in sharpening, always adjust and adapt to make a knife work for YOU.

  4. #34
    Thanks for this thread Dave. May save some of us from going down an a path of
    sharpening/cutting frustration

  5. #35
    Das HandleMeister apicius9's Avatar
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    ##{}{%, this is longer, better thought through and more complicated than most of final papers I am reading right now... And I really only want reasonably sharp knives. Makes me want to reconsider pull-through gizmos again... I still don't see the appeal in sharpening, sometimes it seems way over my small brain's capacity...

    Stefan

  6. #36
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    Quote Originally Posted by geezr View Post
    Thanks for this thread Dave. May save some of us from going down an a path of
    sharpening/cutting frustration
    or pull us back from the brink...

  7. #37
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    So am I correct in saying that when a knife is described as being "90/10 right hand ground" that it means that the cutting edge is 90% offset to the right side? Like if you had a number line (1-2-3-4-5-6-7-8-9-10) that represented the total width of the spine of the knife, the cutting edge is sitting on the 9th place holder?

  8. #38
    This might explain why my Fujiwara FKH Gyuto can shave armchair and glide through printer paper just fine, but wedges like it has superglue on the sides of it when I go to cut carrots/potatoes. Just when I thought I was getting the hang of sharpening, good old Dave brings be back to square 1.
    Twitter: @PeterDaEater

  9. #39
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    Quote Originally Posted by adletson View Post
    So am I correct in saying that when a knife is described as being "90/10 right hand ground" that it means that the cutting edge is 90% offset to the right side? Like if you had a number line (1-2-3-4-5-6-7-8-9-10) that represented the total width of the spine of the knife, the cutting edge is sitting on the 9th place holder?
    yup

  10. #40
    Quote Originally Posted by El Pescador View Post
    yup
    Really? With the spine up, edge down, tip facing away from you, the bevel is farther on the right side than on the left side? This doesn't make sense to me considering that on a right-handed single beveled knife, the edge will be at 0.

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