Sharpening with different grits on opposite sides of the edge

Discussion in 'Maintenance, Tinkering & Embellishment' started by familyphotoshoot, Feb 21, 2021.

  1. familyphotoshoot

    familyphotoshoot

    54
    Aug 29, 2013
    So Pete on the Cedric and Ada YouTube channel was sent a knife to test by a viewer with a pretty unique sharpening method. He sharpens the knife at a forward angle on one side at a very low grit (~250) and once a burr has developed he removes it via strop and then sharpens the other side at a perpendicular angle to the first side at a much higher grit (~6000) and finishes again with a strop. This produces what he calls "nano-serrations" and he says that it's given him great results in edge retention, and the test results in the video seem to show that there is something to this method.

    Here's a drawing he sent of the edge that's being produced:
    [​IMG]

    And here's the video of the edge being tested:


    Have any of you ever heard of or tried something like this?
     
  2. PlumasDePan

    PlumasDePan

    40
    Jul 21, 2020
    Big if true...

    I was also very surprised by this. Like how can this very simple detail has been not noticed until today by so many knife enthusiast and knifemakers around the world
     
  3. PlumasDePan

    PlumasDePan

    40
    Jul 21, 2020
    I was thinking about this.... Maybe the longer edge longevity is not caused by the cross sharpening but instead by not using so meany stones over 600grit. Like finer stones will cause carbide tearout

    In a study by knifesteelnerds it was show that the ideal for a knife wear resistance is 600 grit. And Pete if i don't recall he always goes through all the progression up to a polish bevel

    I would like to see how this compares to m390 normal sharpened to 600 grit
     
  4. Glock Guy

    Glock Guy Gold Member Gold Member

    Jul 28, 2012
    Scalpels are sharpened with 2 different grits, so it isn’t exactly new. It can also be done a few different ways.

    One is by doing each side of the entire bevel in 1 grit. The other is by doing JUST the micro bevel in 2 different grits. In other words, you could bring the entire bevel to 6k grit, the do a micro believe with 1 side coarse and the other polished.

    If you go the micro bevel route you’ll need a good, hard steel, as it won’t be as noticeable (or easy to do accurately) with a softer steel.
     
  5. miso2

    miso2 Gold Member Gold Member

    Nov 19, 2014
  6. HeavyHanded

    HeavyHanded

    Jun 4, 2010
    I'm going to go out on a limb and say the actual edge along the apex will look nothing like the drawing.

    In my experience you get an edge that cuts close to the average of the two edge finishes, but is tougher to deburr. There may be some value in crossing the scratch pattern but even that is somewhat dubious.
     
  7. David Martin

    David Martin Moderator Moderator Gold Member

    Apr 7, 2008
    I thought my results in this ^ effort was somewhat questionable. DM
     
  8. ToddS

    ToddS Basic Member Basic Member

    419
    Jan 15, 2015
    This myth about blades having "teeth" formed by the "scratches" on the bevel just won't die.
     
  9. Blues

    Blues Lapsed SuperMod / Cattle Knife Rustler Staff Member Super Mod

    Oct 2, 1998
    Apparently the myth has teeth of its own.
     
  10. HeavyHanded

    HeavyHanded

    Jun 4, 2010
    Maybe just a question of semantics.

    There definitely are irregularities scratched into the steel both along and across the edge, strongly influenced by the size of the abrasive.
     
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  11. Blues

    Blues Lapsed SuperMod / Cattle Knife Rustler Staff Member Super Mod

    Oct 2, 1998
    Completely agree. I was just having fun with idioms.

    Does that make me idiomatic or simply an idiot?

    (No need to reply...it was a rhetorical question, and besides, I already know the unfortunate answer. :p)
     
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  12. Diemaker

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

    736
    Apr 28, 2017
    The person that made the drawing obviously never looked at that edge with a good microscope. The "teeth" made with a coarse stone look more like a hacksaw blade than a serrated knife, at least with the hard steels I like. There is no fine apex, it's been torn off with the coarse abrasives.
     
  13. HeavyHanded

    HeavyHanded

    Jun 4, 2010
    For it to look like that you'd need to use a single row of abrasive particles...

    But, you do get low spots at the bottom of some scratch troughs, and this also pushes the apex line over a little. There's not much rhyme or reason to it since the best of abrasive surfaces have some variation in depth.
     
  14. Also noticing, as marked in the drawing anyway, the 'polish' on the second side is done with 6000-grit 'silica' particles (as described on the drawing). If so, whatever edge retention improvements that might be noticed may just be due more to burr cleanup with the 'silica', and less about the actual grooves or troughs left by the silica abrasive, which wouldn't likely dig much into a modern steel as pictured. The two knives he's testing in the vid are in M390 (Benchmade) and M4 (Spyderco). Wouldn't expect much from 6000-grit 'silica' abrasive on those, save for the sort of effect one might get by stropping on bare leather, or maybe burnishing on a very fine natural stone (like a black hard Arkansas). A good stropping job to clean up the burrs and weakened remnants could have as much positive effect as anything, for the sake of edge retention in use.
     
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  15. ToddS

    ToddS Basic Member Basic Member

    419
    Jan 15, 2015
    Here is Maxamet sharpened with Wicked Edge 600 grit diamonds. This is very typical of 'non-linear' edges, where the high spots are mostly burrs and the low spots are mostly chips.
    If you hunt, you might occasionally find a feature that looks like a serration, but it's just not typical in most situations. First problem is that the grit just doesn't penetrate that far, second problem is that most of these "scratches" are burnishing lines, not grinding lines.
    As HeavyHanded pointed out, you need a very small number of abrasives, like a single row (think cheese grater) to get sufficient penetration to make something simulating a serrated edge. Softer steel would help too.




    [​IMG]

    [​IMG]

    [​IMG]

    [​IMG]
     
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  16. Diemaker

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

    736
    Apr 28, 2017
    And that is a 600 grit. Think of what it would look like with a coarse stone.

    PS - Nice clean images!
     
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  17. scottc3

    scottc3 Gold Member Gold Member

    542
    Oct 11, 2014
    PlumasDePan, Pete's spreadsheet has some angle results by steel, and I got some insight from the VLOG's as he went to 12 degrees.

    Watched Pete's m390 video a couple times, and the M2 test just now. His results, the BF link, comments and SEM's above, make me scratch my head thinking what questions would answers directly his two impressive ~1000 cut test results. His spreadsheet of past m390 / M4 rope cut tests reports ~400 thru ~800 cuts. Pete's often stated caveat regarding his results - a dude in his garage testing edges-, argues for understanding results as trends, patterns and principals, not doctoral research. Gab's written and oral reports, efforts, and satisfaction leave questions, even though he demonstrates that toothy edges have there place. Could different results be attributed to the following? And what am I missing?:
    • Pete's sharpening procedure results for Benchmade's m390 / M4 vs. Gab's procedure, within Pete's testing methods-
    • Beyond comments characterizing 6k silica stones effect on m390 /M4, and comments / images of burnishing vs grinding Maxamet with Wicked Edge's 600 diamond grit, is there any effects from Gab's apex creation using different stone types for each side? - diamond for 70µ side, and silica's 3µ side.
    • Gab's procedure is similar to several other techniques mentioned above, taking advantage of bevel face counts / facets treatments to increase and maintain cutting effectiveness.
      • Production of an "open edge" thin geometry scalpel, treating both sides differently ("open edge" scalpel blade describes a surgical blade ground on both sides, but only finished on one.... comes with microscopic teeth along the blade’s cutting edge, which gives a surgeon a consistent feel while making an incision. Open-edge blades tend to be more durable and hold their edges longer.") usamedicalsurgical
    • Missing info-
      • Gab's m390 / M4 grind angle;
      • specific start state for edge tested before Gab applied procedure;
      • Gab does not report his own before and after results, but states generally " it's given him great results in edge retention."
    Aside - finishing up Tufft's "Beautiful Evidence" to help the family understand the gulf between signal and noise, beauty and base, truth and lie, and want to say thx to folks (Pete and Gab Et al.) attempting to increase signal, beauty, and truth. Stay free, out of our liberty we stand with hope-
     
  18. 000Robert

    000Robert Gold Member Gold Member

    Mar 28, 2020
    Sounds like gobbledygook to me.
     
  19. Sonnydaze

    Sonnydaze Gold Member Gold Member

    Jul 6, 2009
    I'm out in left field...sitting down...waiting for some dude to hit the damned ball.
     
  20. Gritomatic

    Gritomatic Dealer / Materials Provider Dealer / Materials Provider

    266
    Jan 4, 2016
    "There is no bigger eye-opener than a good 20X loupe on a freshly sharpened blade." (c) not me

    Microserration created by asymmetrical sharpening has two applications: scalpels and rope cutting competitions. Microserration wins competitions because of the cutting performance, not the edge retention that is very bad. People who studied the topic gave up after their first injuries. Hacksaw profile micro-serrator IS traumatic. Good for scalpels only.
     

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