Edge dulling very quickly

Discussion in 'Sharpening Station' started by justin bray, Dec 30, 2018.

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  1. Dec 30, 2018 #1

    justin bray

    justin bray

    justin bray

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    Hey there! I just bought a masakage Koishi AS Gyuto and I love it.

    I am a professional cook in a high end Japanese restaurant so I need my knife sharp.

    I Sharpen everyday, on a chosera 3k and a cerax 1000. I have built muscle memory and I can produce an edge that is sharp to pass the nail biting, paper cutting and hair shaving tests.

    The problem I have is maintaining it. If I use the knife to do a few small tasks, nothing major or anything(cut onions on a poly board, slice meat), the knife no longer passes those tests, or it notably does worse.

    The knife never gets really dull, but it definitely is sliding on my nail unless I use some pressure.

    Is this normal? I would like an edge that could pass the fingernail tests after a day of light work. Is that not reasonable?

    I am wondering if you guys had any idea on what a cause may be? If I barely touch up(3 strops) on a chosera 3k it then passes the fingernail test again, then will fail it after say slicing a few steaks or veg. It's so strange to me. Am I crazy?

    Any help is appreciated! Thank you!
     
  2. Dec 30, 2018 #2

    Knife2meatu

    Knife2meatu

    Knife2meatu

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    You're most likely not deburring properly; and then you're presumably just re-sharpening that same wire-edge -- that all at once explains the a) high initial sharpness; b) poor edge retention; c) easy re-"sharpening".

    You can test for the wire edge easily by gently pressing the flat of your fingernail against the side of the edge: this allows you to deflect the edge slightly to check for thinness; a foil edge offers virtually no resistance to the lateral push.
     
  3. Dec 30, 2018 #3

    refcast

    refcast

    refcast

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    New knives can have this wire edge type thing happen. I guess it's from the heat treat -- the outermost layer of steel is different than what's inside. Once you get past this, no crazy-tough wire edges seem to form for most well-treated steels.

    Just keep on sharpening until that bothersome steel is removed. At this point, any edge retention issues that may happen would be due to chipping, too thin behind the edge, or misuse (which i don't think is the case here).

    The wire edge is sharp in the 'sharpness' tests because they don't involve a lot of force -- unlike cutting steak or onions. That amount of force is enough to wobble the wire edge over, at which point there is no sharp edge cutting though the food. At least when I experienced in my case.


    Deburring/Refinement:
    Keep your fingers as close to the edge as possible. Closer the better! Push/pull then edge parallel strokes. Repeat with lighter pressure, shorter, smaller movements. Even if the knife doesn't move, there is still force there for the final refinement/deburring! Repeat until burr is removed and until your final stone. If the burr is tenacious, yeah, you can continue to use heavier pressure. The refinement is important because it makes a cleaner edge, which means in use loose pieces of metal don't get ripped off -- so a tougher and sharper edge. Also the remaining steel is seems to be less 'fatigued' during sharpening.

    This should work . . . but you can see.
     
  4. Dec 30, 2018 #4

    zitangy

    zitangy

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    possibilities that comes to my mind...

    a) if there is a burr problem or an uncurled burr , i wld attempt to eliminate it with an alternating and edge leading strokes as this wld tend to "cut" the burr away. Hopefully this solves the problem as spine leading wld just uncurl any burrs

    b) if this does not work, you may try creating an entirely new fresh edge, the abrading it 90 degrees to the stone quite lightly and then resharpen the edge.

    AS steel shld always be bitey enough and this is suppose to be ard 64 hrc. and thus good edge retention

    hope it works... Z
     
  5. Dec 31, 2018 #5

    Benuser

    Benuser

    Benuser

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    You may have overlooked a micro-bevel, factory buffering may have fatigued the steel, wire edge...
    In any case, make sure to have fresh steel and get rid of that factory edge. Take a good coarse stone and go on: create a fat burr, remove it very lightly with a much finer stone and start on the other side. From now on at least you're sure the old edge is gone.
    Even with common maintenance I start sharpening AS — very lightly this time — on a medium-coarse stone. Not to remove a lot of steel, but it contributes in some way to a much better end result, a higher edge stability. Must have to do with tungsten carbides. Got the trick here and it works.
     
  6. Dec 31, 2018 #6

    gman

    gman

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    i have the same knife. as others have said, deburring is really important. too much pressure on your finest stone will continue to work up a burr instead of removing it. a light touch at the end does wonders. i also strop on leather with 1 micron paste, and the end result is a knife that will pass the fingernail test for 2-3 months of home use (if i let it go that long).
     
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  7. Dec 31, 2018 #7

    justin bray

    justin bray

    justin bray

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    Thank you everyone !I'll try all these suggestions. Hopefully it's just a hard burr to remove
     
  8. Dec 31, 2018 #8

    labor of love

    labor of love

    labor of love

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    A simple wine cork could be your best friend here.
     
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  9. Jan 12, 2019 #9

    rick alen

    rick alen

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    For some perspective, my Takamura and Kagero PM steel knives took a good dozen [light] sharpenings to get past the "factory" edge to something relatively stable in terms of microchipping.
     
  10. Jan 13, 2019 #10

    inferno

    inferno

    inferno

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    look up bob kramers sharpening vid where he does one stroke on each side and switches side of the blade each and every swipe on the stone (no need to deburr/strop then). also use very light pressure the last 10-20 swipes or so. basically the last swipe determines the final edge. surprise surprise...

    5 minutes in

    also: a good knife will last one shift or so i heard. thats it.
    knives actually goes dull by just cutting 2 cuts of cardboard comparatively. all steel does.
     

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