Chopping boards and Self-Improved Sharpness phenomenon

Discussion in 'Maintenance, Tinkering & Embellishment' started by wootzblade, May 14, 2019.

  1. Diemaker

    Diemaker KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Apr 28, 2017
    I can't imagine polyethelene spliting like this. It takes certain conditions and speed to get metal to shear like this in chip formation when machining.
  2. wootzblade


    Feb 24, 2014
    The effect is pretty much clear now thanks to what have been said by Miso, HeavyHanded, Obsessed with Edges, and Bluntcut.
    I am also adding here what Jan from Czechia wrote, as we know by SEM that the 1-micron diamond leaves near 0.1 micron scratches:

    "In my understanding deburring a knife edge using low speed hard felt wheel impregnated with 1 micron diamond abrasive results in edge
    surface with roughness cca 0.1 micron. That can be considered a nice, smooth surface, until we realize, that the apex diameter is only
    some 0.2 micron (for edge with BESS score 100).
    The experiment shows that repeated movement of the edge in a 32⁰ V groove can remove/smooth some residual edge surface irregularities and lower the BESS score. "

    Summarizing all that, we can say that the sharpness-improving effect of edge-friendly chopping boards is due to burnishing of the metal off the sides of the edge near the apex in the tiny grooves in the board, and smoothing off the apex irregularities.
    Chris "Anagarika" likes this.
  3. miso2

    miso2 Gold Member Gold Member

    Nov 19, 2014

    Do you think plastic actually refines the edge like stropping or just the sides?
    I guess either can improve the score on the tester using 0.2~0.3 mm thick cut medium.

    But if the effect goes all the way to the edge, it may work as an alternative stropping method.
    I would be curious if you can see burnishing at very very near the edge at the light microscopy level.
    Chris "Anagarika" likes this.
  4. wootzblade


    Feb 24, 2014
    We've stumbled across a method to refine the edge, that thanks to our research of the chopping boards had been proved even before we realized we discovered it.
    In the coming weeks I am going to experiment with various plastics and grooves to pick the best material.

    Thank you everyone, it is an exciting side-finding in our chopping board research.
    Last edited: May 19, 2019
    Night Rider likes this.
  5. wootzblade


    Feb 24, 2014
    Update: the edge-hostile plastic board has been identified as Low-density Polypropylene.
    The video shows how we actually do the sliding cuts on the test boards:
    Last edited: May 18, 2019
    filedog and bucketstove like this.
  6. bucketstove


    Sep 23, 2014
  7. wootzblade


    Feb 24, 2014
    In the producer's tutorial videos on YouTube we see highly repeatable scores when they test a production DE razor - but try yourself to test the same razor on the same instrument... you may well get a different score.

    When someone gets the BESS sharpness tester, in the beginning his sharpness scores taken on the same point on the edge can be anything, the variance is huge, but with practice it narrows down.
    The more testing one does, the more repeatable become his scores; the problem is however that it is repeatable within his own habit of tensioning the test line, and will not be exactly the same as someone's else.

    The otherwise near perfect instrument has a single source of inaccuracy - the test fixture (ATF), and improving it could mitigate the issues with repeatability.

    But it still works wonders, this instrument.
    As I've explained, one can relatively quickly make the tester scores repeatable within his personal "standard" - and use it for improving his sharpening technique, and for comparative studies of various blades. Tons of valuable data have already been gathered this way.
    bucketstove likes this.
  8. bucketstove


    Sep 23, 2014
    So how repeatable are your scores?
    In data table you post averages, what is the standard deviation?
  9. wootzblade


    Feb 24, 2014
    Factory edge usually shows greater variance on the tester than the re-sharpened and thoroughly deburred edge.
    3 sharpness measurements were taken in the same point of the edge, approximately of course.
    Examples from the test logs for factory edge vs resharpened:


    Acacia long-grain
    Initial sharpness 110, 140, 125 BESS
    After 2000 cuts 135, 110, 100

    Acacia end-grain
    Initial sharpness 130, 135, 130 BESS
    After 2000 cuts 110, 105, 115

    Bamboo long-grain
    Initial sharpness 195, 200, 190 BESS
    After 2000 cuts 180, 175, 165

    Bamboo end-grain
    Initial sharpness 165, 155, 175 BESS
    After 2000 cuts 240, 185, 210

    Yoshihiro Hi-Soft polyvinyl acetate
    Initial sharpness 145, 185, 150 BESS
    After 2000 cuts 125, 105, 115

    High Density polypropylene
    Initial sharpness 115, 125, 120 BESS
    After 2000 cuts 70, 75, 70

    Low Density polypropylene
    Initial sharpness 110, 125, 120 BESS
    After 2000 cuts 200, 195, 190

    Low Density polyethylene
    Initial sharpness 120, 125, 120 BESS
    After 2000 cuts 90, 85, 95

    Low Density polyethylene
    Initial sharpness 110, 110, 110 BESS
    After 2000 cuts 65, 70, 65
    Last edited: May 24, 2019
    bucketstove likes this.
  10. lutejones


    Mar 15, 2007
    Super interesting, it seems that the groove on the cutting board is behaving like very light passes on a smooth steel.
    It should be cool seeing it under magnification, could some adhesive wear be happening?
  11. HeavyHanded


    Jun 4, 2010
    A slow turning wooden wheel might be nice finisher, just touch the edge to it and run with the grain.
  12. wootzblade


    Feb 24, 2014
    In my experience, hard honing wheels are less practical than somewhat pliable. The last wheel you've ground the edge on, hardly ever is a complete match to the wheel you are honing on, and because of that the ground edge profile usually does not match the honing wheel profile completely; some pliancy of the wheel surface helps. Stone, glass, wood, and even MDF honing wheels aren't as good for finishing as leather, hard felt and paper wheels.
    Last edited: May 25, 2019
    Mr.Wizard likes this.
  13. HeavyHanded


    Jun 4, 2010
    I mean actually make contact edgewise, not across. Mimic the effect of many sliding cuts. I am dubious this would actually work, but no good reason it shouldn't if the mechanism is correctly theorized.
    Mr.Wizard likes this.

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