Pressure on trailing stroke vs. push stroke

Discussion in 'Sharpening Station' started by gyutorific, Feb 10, 2019.

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  1. Feb 10, 2019 #1

    gyutorific

    gyutorific

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    I've heard/seen the following sharpening advice regarding the amount of pressure to apply on the pull/trailing stroke vs. the push/cutting stroke:

    1. Apply more pressure on the pull/trailing stroke
    2. Appl;y more pressure on the push/cutting stroke
    3. Apply equal pressure on both strokes

    These people never explain why they do it like they do.

    = Confusion

    I suppose there are complexities with the type of knife, steel, stone grit, stone composition, angles, etc. Fair enough. (Stropping on leather with a *trailing* stroke (for obvious reasons) seems to be the only universal.)

    Anyone care to clear things up for me/us?

    Thanks,

    James
     
  2. Feb 10, 2019 #2

    Midsummer

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    I do not know what is right in an absolute sense. I am pleased with the level of sharpness I can obtain and have compared it to other peoples efforts. I am interested in replies from some of the great sharpeners.

    I find that I can maintain the angle better if I apply heavy pressure only on edge trailing strokes. I tend to wobble more on the edge leading ones. So I try to do most of the sharpening(ie apply pressure) on the edge trailing strokes were my knife to stone angle is more consistent.
     
  3. Feb 10, 2019 #3

    refcast

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    1. Apply more pressure on the pull/trailing stroke
    This makes sure that there are no particles in front of the edge to collide with it and dull it. However, this means that the steel can bend, so the very edge doesn't contact the stone as strongly, and the burr is just a bit more likely to stay. I think this lets the edge refine more, assuming the burr is removed. Prevents biting into the stone, especially at high angles or pressure.

    2. Apply more pressure on the push/cutting stroke
    This makes the very edge collide directly with bound and loose abrasive, which makes a fresh edge. But that fresh edge can bite into the stone deeper, which dulls it a bit or sharpens it (depends on how you look at it) and loose particles can collide and dull it, which does help burr removal though. I think this has less potential for maximum sharpness, but it's better for removing or minimizing a burr.

    3. Apply equal pressure on both strokes

    Both phenomena above happen about equally.

    *4. Deburr using edge parallel strokes
    Edge no longer has teeth but is really smooth. I guess the ultimate or very last burr removal step, good for only the final burr stuff but not good for giant burr at lower grits.

    Just apply these concepts to stropping and yeah, we see that only edge trailing makes sense, cause edge leading will just bite into the leather and dull itself (or does it? I'll try it carefully some time)
     
  4. Feb 10, 2019 #4

    milkbaby

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    I'm not a great sharpener, but I do follow the school of pressure on the edge trailing direction but not on the edge leading. This is because it's possible to "bite" the stone with edge leading pressure, so I generally avoid it. If you are super consistent with angle though, I doubt it matters much in general. I'm sure on YouTube you can find some examples of crazy sharp knives that were sharpened with only edge leading strokes.

    I also like the traditional Japanese back and forth "scrubbing" motion whereas some people only go in one direction and lift the knife up to start another of the same stroke. To me, when the knife is always in contact with the stone, it feels easier to maintain the angle than if i did one stroke, lifted up, and repeated.

    Go watch Jon Broida of Japanese Knife Imports on YouTube. He always explains the whys behind what he's doing, so you get the concept. When you can fully understand the reasons behind what's being done, you can adjust your sharpening to your own preferences. For example, if you understand the concept that the angle must be consistent, then in general it doesn't matter if you apply pressure on only edge trailing, edge leading, or both directions.
     
  5. Feb 12, 2019 #5

    nutmeg

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    I prefer trying to apply the same pressure back and forth in order to stay focused on the angle and finish the job quicker.
     
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  6. Feb 12, 2019 #6

    aaamax

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    This^
    And once you build up a rhythm, there is no thinking involved. That is why sharpening is almost meditative. Love it!
    Side note for you Jnts weirdos out there... how many of you sniff your stone before using. Especially when you first get started? OOpps, too much information? lol.
    Cheers.
     
  7. Feb 12, 2019 #7

    Luftmensch

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    They do it like they do it because that is the way they like to do it?

    ¯\_(ツ)_/¯

    While there are good basics and common sense, there are many routes to a good edge. I don't think there is an absolute truth here. Style boils down to individual preference - which is likely a complex mixture of how people learned, their dexterity and hand dominance. Within a sensible range, I dont think there has to be an objective explanation beyond that?

    For what it is worth*, on low grits I will use more pressure on push strokes for aggressive material removal. For the rest (medium and high grits) I would say I aim to achieve a symmetric pressure. I will also tend to finish using only very light push strokes on a high grit stone. But hey... thats just me. That was my route to a comfortable, competent and repeatable edge.


    * I consider myself an intermediate sharpener (I really have no basis for comparison)... I am certainly no artisan but I am well beyond the learning phase. I think the most important milestone is achieving consistency no matter the 'style'. From there it is easier to experiment with different pressures and strokes to find out what is both comfortable and effective (though I suppose the whole learning process is coupled).
     
  8. Feb 12, 2019 #8

    Dbjames123

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    You should not apply any pressure on the pull stroke. Your causing the blade to dig. Your removing the work you do. If you watch japanes sharpeners they actually will tell you to apply hard pressure on your push and actually pick the knife up and on the pull stroke. Subsequently lessening pressure as you move up grit
     
  9. Feb 12, 2019 #9

    Mucho Bocho

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    I've heard this too, though Jon has commented very little on stroke pressure for double bevel knives. I thought stroke pressure was only really critical on single bevel knives.
     
  10. Feb 12, 2019 #10

    Grunt173

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    Is that what you meant to say or do you have your push and pull backwards?
     
  11. Feb 12, 2019 #11

    Dbjames123

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    Your only applying pressure when your going away from the edge. So its changes between sides. Also always moving your fingers across the blade applying pressure evenly on every spot. If you only apply pressure at the tip and heel the middle will not get enough work.
     
  12. Feb 12, 2019 #12

    Dbjames123

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    If the edge is pointed away your applying pressure on the pull and if the edge is pointed toward you then you are only applying pressure in the push. Sorry for the confusion
     
  13. Feb 12, 2019 #13

    Dbjames123

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    Pressure is most important on low grit stones. When you get stones for finishing around 8000 and above I personally let the weight of my knife do the work. At that point your mostly removing burrs, making a micro bevel, and polishing.
     
  14. Feb 12, 2019 #14

    Dbjames123

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    Korins videos on YouTube could really run this down easily for you.
     
  15. Feb 12, 2019 #15

    Luftmensch

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    Hehe for clarity perhaps 'edge-leading' and 'edge-trailing' is more precise than 'push' and 'pull'

    (I am guilty of this above)
     
  16. Feb 12, 2019 #16

    Dbjames123

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    Good point
     
  17. Feb 12, 2019 #17

    Grunt173

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    Ok got ya.I am so use to terms,edge leading and edge trailing. That covers both the sharpeners that use either one hand or swap hands for sharpening.
     
  18. Feb 12, 2019 #18

    Luftmensch

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    As I understand it, when honing the back of single bevel knives, an important objective is to preserve the flat region (uraoshi) around the hollow (ura). When working on the back, lowering the pressure of spine leading strokes helps reduce the amount of material removed from the uraoshi at the spine. If a lot of pressure is applied on spine leading strokes, the uraoshi at the spine gets wider faster than it should. This is bad as now there is a greater surface area of hard steel in contact with the stone. This will make each subsequent honing more difficult. It also ruins the aesthetic of the uraoshi.

    I think the important thing to note is that the uraoshi at the spine can only be modified from one side (practically speaking). You cant make the uraoshi at the spine thinner unless you regrind the hollow. The uraoshi at the edge can be modified from both sides. While you don't want to remove any more material than you have to when honing the uraoshi at the edge, at least you can make it thinner by attacking it from the front. This is what happens when you hone the primary bevel on the front (kireha). As you grind material away, you are bringing both the cutting edge and the shinogi line (angle change between the primary bevel and blade face) up towards the spine. This has the effect of making the uraoshi at the edge thinner.

    To try and preserve the uraoshi and depth of the ura, only high grit stones are used when working on the back.

    As for working on the primary bevel at the front.... I am not so sure pressure needs to be moderated between edge-leading and edge trailing strokes. I don't see a big need for it. There are some angle differences, related to maintaining the convexity of the bevel (hamaguri grind), but i don't think pressure plays a large role in this.




    Caveat emptor: I'll leave it to a certified guru to give a more authoritative explanation. I may be wrong. This opinion is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE*.

    * For the other, 98%, this is a GPL joke...

    Hey @Mucho Bocho, I don't mean to jargon-splain to you. I am sure you know these terms. I thought being explicit might be educational for future readers and new comers to kataba (single-bevel) knives.
     
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  19. Feb 12, 2019 #19

    Michi

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    Right. Translation: "Don't blame us if it doesn't cut. We only made the knife."

    Applies not only to GPL, unfortunately… :(
     
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  20. Feb 14, 2019 #20

    refcast

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    Just as a test to what I said, I did try edge leading on leather to touch up a razor. Reverse stropping if you will. VERREREYREy carefully. Like a mm or so in stroke length, blade angle almost parallel, with enough pressure to sink in just slightly to round the leather over to the edge.

    A great edge, definitely doing this in the future. Sure beats regular stropping for final refinement. Actually got those pesky little stubbles out...
     
  21. Feb 14, 2019 #21

    Luftmensch

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    That is bold of you. What is the surface texture of your strop? Is it the grain side (smooth) or flesh side (fibrous) of the leather? I imagine it would be harder to reverse strop on the fibrous side.
     
  22. Feb 14, 2019 #22

    K813zra

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    I am a pressure on the trailing stroke and release on the leading stroke kind of guy on most knives. Why, simply because that is what feels most natural to me and gets me the best edge much of the time. There are exceptions. Very short blades with a lot of belly are easier, for me, to do leading strokes while getting the belly well. Knives like my pocket/edc knives I sharpen like this.

    As for lateral strokes, this is something I learned from Jon over at JKI by watching his videos. As another poster said, this seems to work really well with tiny bits of burr. Not so much with huge starting burrs. Those get abraded off over time.

    In short, why I or others do what we do is simply because it is what we are comfortable with. Me, I based my sharpening technique, initially, off of what I saw others do and adapted it to my own needs over time. I simply go with what works.
     
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  23. Feb 14, 2019 #23

    Grunt173

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    Edge trailing pressure for me and zero to light pressure on the leading stroke and I would never think of edge leading for stropping on my 2 foot long Kangaroo strop.Just the thought of that sends chills up my spine.
     
  24. Feb 14, 2019 #24

    refcast

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    The smooth side. Yeah, though cutting into it--dangerous!
     

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