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Testing Sharpness After Sharpening

Discussion in 'Sharpening Stuff -- Stones, Strops, and Systems' started by awyeah, Sep 6, 2019.

  1. awyeah

    awyeah Empty Pockets

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    New to sharpening. How do you all test your knives after sharpening to know that they are indeed sharp?
     
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  2. A.B.

    A.B. Loaded Pockets

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    Well, if I can shave my arm hair they are pretty much good to go. Cheers

    Verstuurd vanaf mijn SM-G950F met Tapatalk
     
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  3. PragmaticMurphyist

    PragmaticMurphyist Loaded Pockets

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    Stage 1 - slice cut (moving the blade front to back and vice versa) copier paper
    Stage 2 - push cut copier paper (various points on the blade)
    Stage 3 - slice cut phone book paper
    Stage 4 - push cut phone book paper

    If the paper tears then it's a fail at that stage.

    ...but yeah, I generally put bald spots on my left arm too!

    (Note - there's a difference between "shaving" and "ripping hairs out at the roots". Aim for the former.)
     
    Last edited by PragmaticMurphyist, Sep 7, 2019
    #3 PragmaticMurphyist, Sep 7, 2019
    Last edited: Sep 7, 2019
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  4. eugenechia1989

    eugenechia1989 Loaded Pockets

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    Just some tests I do.

    1. I use a flashlight to illuminate the edge. It should not reflect light. The edge should either be a very fine black line or be barely visible at all. Theoretically, the sharper the edge, the less visible it will be.

    2. I shave arm or leg hair. It should pop the hairs off without hesitation.

    3. I slice newspaper slowly and using the entire cutting edge, listening for any inconsistencies in the sound it makes. Theoretically, the sharper the edge, the higher the pitch of the sound it makes, and any changes in pitch should highlight inconsistent sharpness along the edge.

    4. I push-cut newspaper. It's quite challenging, to be honest, particularly with chunkier blade grinds. My saber-ground Endura 4 always struggles with this test, even when it aces the other tests. I sometimes have to slice a bit first and then push.

    5. I do curvy push-cuts through printer / copier paper. I like an S-shaped motion myself.
     
    Last edited by eugenechia1989, Sep 7, 2019
    #4 eugenechia1989, Sep 7, 2019
    Last edited: Sep 7, 2019
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  5. neo71665

    neo71665 Loaded Pockets

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    Arm shave
     
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  6. ccwaters

    ccwaters Loaded Pockets

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  7. ccwaters

    ccwaters Loaded Pockets

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    I only take my edges down to 5 micron finish, here is a shot of a master testing a mirror edge, which If I recall correctly is about .1 micron look up Michael Christy Youtube.

    Lots of good sharpening, edge retention/testing videos.

    The hair in my picture is short, dry and brittle.

    Does the average person need a knife taken to this extreme? Probably not but it does stay sharp longer than a lesser edge.

    [​IMG]
     
  8. Moshe ben David

    Moshe ben David Loaded Pockets

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    All of the above are both practical and economical methods of testing sharpness. Yes, may be somewhat subjective, but when you use the same methods consistently it will give you a pretty solid idea of how your sharpening is doing.

    IF - I did say IF - you feel you need something that gives laboratory type data, there are devices out there. I've been seeing certain YouTubers using a device made by Beiss called the Edge On Up PT50B. Here are a couple of links:

    (this is the BirdShot IV YouTube channel. Husband and wife team who test knives, lights and other edc gear....)

    http://edgeonup.com/index.html get the Edge On Up PT50B here

    I am a fan of BirdShot IV; but I do not have any personal experience with the device. FYI

    L'chaim!

    Moshe ben David
     
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  9. PragmaticMurphyist

    PragmaticMurphyist Loaded Pockets

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    Oh, don't show me things like this! :eek:

    Turning sharpening into a game with high scores (or, in this case, low scores)? This and a pinch of OCD and my evenings would be toast!

    :D
     
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