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Knife blade physics

Discussion in 'General Knife Discussion' started by bryan123, Oct 11, 2017.

  1. bryan123

    bryan123

    178
    Feb 7, 2017
    I've been wondering about this.

    At the very edge of a sharp blade, how many atoms width are we talking about? Tens? Hundreds? Thousands?

    Thanks
     
  2. Danke42

    Danke42

    Feb 10, 2015
    5-50 atoms.
     
    Korean Hog likes this.
  3. marcinek

    marcinek

    Jan 9, 2007
    8
     
    LEGION 12 and jbmonkey like this.
  4. 3fifty7

    3fifty7 Gold Member Gold Member

    Dec 24, 2016
    30,276
     
  5. marcinek

    marcinek

    Jan 9, 2007
    And define "at the very edge" if you would.

    It's kinda a "How many angels can dance on the point of a needle?" question.
     
    palonej and Korean Hog like this.
  6. retzius

    retzius

    Sep 17, 2009
  7. bt93

    bt93

    May 12, 2015
    If you go by the single atom theory, it's only one.
     
    LEGION 12 likes this.
  8. Insipid Moniker

    Insipid Moniker Gold Member Gold Member

    Feb 28, 2011
    Probably better to use microns as a unit of measure, as atoms aren't a single uniform size and, since we're dealing with molecules, aren't real helpful anyway. Even then, I suspect it would be really difficult to accurately measure.
     
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  9. SpySmasher

    SpySmasher Lead Guitar

    Sep 1, 2016
    When I sharpen, a buttload.
     
    LG&M, palonej, marcinek and 4 others like this.
  10. Twindog

    Twindog Gold Member Gold Member

    Apr 6, 2004
    You can't get a definite answer because the width of a sharp apex varies quite a bit, say from 0.5 to 1 micron.

    And the diameter of an atom is not easy to calculate, either, because there is no easily defined outer boundary of an atom.

    But if you say a really sharp apex is 0.5 microns wide, you can get an idea. 0.5 microns is 500 nm. An atom of iron is about 140 picometers, or 0.14 nanometers in diameter. So you could have 3,571 iron atoms side by side across the entire apex of a sharp edge that is half a micron wide.
     
    LG&M, Korean Hog, number9 and 3 others like this.
  11. dsalazar

    dsalazar Gold Member Gold Member

    963
    Jun 22, 2017
    What he said
     
  12. shinyedges

    shinyedges Unfaltering Love & Undeviating Will Platinum Member

    Jun 5, 2012
    Who the hell is a tom and what does he have to do with knife edges?

    I don't know knifes a tom count.
     
    palonej and danbot like this.
  13. ScooterG

    ScooterG You mean Ireland? Yeah, it’s mine. Gold Member

    Mar 15, 2016
    From the bottom of a perfectly hollow ground blade:
    1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144
     
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  14. oldtymer

    oldtymer Gold Member Gold Member

    Feb 7, 2014
    Enough to make you say OUCH! if you slip:eek:
     
  15. bdmicarta

    bdmicarta Gold Member Gold Member

    Feb 16, 2012
    Molecules of what?
     
  16. Insipid Moniker

    Insipid Moniker Gold Member Gold Member

    Feb 28, 2011
    Steel, I would presume, though I suppose it could be a different blade material.
     
  17. W. Anderson

    W. Anderson Basic Member Basic Member

    Jun 22, 2016
    Dependent on carbide size I'd guess, but you're not gonna have an edge that is a countable amount of 'atoms' thick any time this century, or next.
     
  18. abcdef

    abcdef

    Oct 28, 2005
    Depending on what you mean by "sharp" and "at the very edge", I suppose it could be an elementary particle or fundamental particle. In particle physics, an elementary particle or fundamental particle is a particle not known to have any substructure, thus it is not known to be made up of smaller particles. If an elementary particle truly has no substructure, then it is one of the basic building blocks of the universe from which all other particles are made. In the Standard Model of particle physics, the elementary particles include the fundamental fermions (including quarks, leptons, and their antiparticles), and the fundamental bosons (including gauge bosons and the Higgs boson). Although elementary particles are not made up of smaller particles, some of them may change to lighter particles (according to specific rules). Yeah, I plagiarized.
     
  19. Bill1170

    Bill1170 Gold Member Gold Member

    Dec 20, 2007
    Atoms and molecules are extremely small in relation to the much coarser crystalline structure of steels. The granularity of the crystals will limit apex radius long before you get down to atomic scale. Now if you want really sharp edges, glass is the way to go because it lacks the crystalline structure found in metals. Obsidian (a naturally occurring glass) is used for tiny neurosurgery scalpels for this reason.
     
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  20. W. Anderson

    W. Anderson Basic Member Basic Member

    Jun 22, 2016
    Only for veterinary use, however.
     
    Korean Hog likes this.

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