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Converting Grit to Microns

Discussion in 'Maintenance, Tinkering & Embellishment' started by TheBishop, Apr 7, 2012.

  1. TheBishop


    Aug 27, 2009
    Something handy I ran across:


      • 1 Determine the particle's grit size. Let's assume a grit size of 3,000.

      • 2 Raise your grit size to the (-0.93589)th power. The easiest way to carry out this mathematical operation is to use the caret symbol ("^"), typing your numbers into a Google search bar.
        3,000 ^ -0.93589
        = 0.000556925

      • 3 Multiply your answer by 11764.7

        0.000556925 * 11764.7
        = approximately 6.5 microns

  2. hardheart


    Sep 19, 2001
    There are multiple grit 'standards' so this actually will not work for many/most abrasives. There are a lot of conversion charts online, including one stickied at the top of this sub-forum. Nice that you shared this, though.
  3. TheBishop


    Aug 27, 2009
    Thanks Hardheart ... I'm noticing this.
    Question if OK.
    Ran across this on ECON:

    Our super fine sanding belts are available in grades from 1800 to 12000 grit. Perfect for knives, marble, solid surface, metals and much more. As always our belts are made with a "non-directional" butt splice. NOTE: First grit size listed is the Super fine grit/the second is the standardized U.S. grit equivalent.

    2730001 1X30 1301800 BELTS 1 X 30 SF PACK OF 6 1800/600
    2730002 1X30 1302400 BELTS 1 X 30 SF PACK OF 6 2400/1000
    2730003 1X30 1303200 BELTS 1 X 30 SF PACK OF 6 3200/1200
    2730004 1X30 1303600 BELTS 1 X 30 SF PACK OF 6 3600/1350
    2730005 1X30 1304000 BELTS 1 X 30 SF PACK OF 6 4000/1500
    2730006 1X30 1306000 BELTS 1 X 30 SF PACK OF 6 6000/1800
    2730007 1X30 1308000 BELTS 1 X 30 SF PACK OF 6 8000/2000
    2730008 1X30 13012000 BELTS 1 X 30 SF PACK OF 6 12000/2500

    So, would the 12,000 grit only come out to what is accepted as 2500 grit?
    Cause if it a true 12000 grit, we are getting into some seriously low microns ... confusing wording.
  4. unit


    Nov 22, 2009
    My suggestion is to not attempt to correlate between suppliers.

    Different abrasives work differently, AND different suppliers arrive at nomenclature differently (or at least it seems that way).

    a quick google of grit size leads you to numerous "resources" in the form of various charts and classification systems, and it is evident that confusion could result a number of ways.

    My rule of thumb is to stick with one supplier for media (i.e. I do not switch from 3M, to DMT, to Spyderco, then back to DMT, then 3M as I go through my progression during a polish job). Perhaps this results in a company monopolizing me, but it works and it eliminates a lot of homework and time to get consistent results.

    There are many ways to do a job well, we do not all necessarily have the same "best" way. Hope this helps...
  5. At times, even within one manufacturer, the 'stated' particle/grit/mesh sizes are almost arbitrary. The best example of this, is Spyderco's own ceramic hones in medium, fine, and EF 'grit'. Each actually uses the same exact abrasive particle size. Only the manufacturing process and surface finish of the hones make each perform to a 'medium', 'fine' or Extra Fine' finish.

    The comment quoted below is from Sal Glesser himself, in a similar discussion on Spyderco's own forum:

  6. Lagrangian


    Jun 25, 2011
    This is a very complicated subject.

    Within a single mesh size, there are smaller and larger particles. The mesh size is basically the median size of particles _by weight_. (I'm throwing away some details here.) Beyond that, the actual distribution of particle sizes has very little restrictions, according to most official engineering standards.

    What we're really interested in is the distribution of scratch sizes produced by an abrasive (is the distribution very uniform, very non-uniform, with a single peak, with multiple peaks?). This turns out to be very complicated too. Here is just a brief partial list of things that affect scratch size:

    1. Particle size
    2. Particle hardness
    3. Particle friability (how easily it breaks into smaller particles)
    4. Particle shape (round and smooth, blocky, or thin and splintery?)
    5. Bonding medium (vitrified, sandpaper, loose, leather, etc.)
    6. Aggregation (whether or not small particles (say in solution or paste) tend to clump together and basically form a "big" particle).
    7. The properties of the materical you are abrading away (cast iron, carbon steel, stainless steel, ceramic,...)

    As a result, it becomes very hard to compare one grit size with another if you change manufacturers, and/or abrasive materials (diamond, SiC, AlO). Sadly, the official engineering stanards are very loose and unrestricted (JIS, FEPA, ANSI).

    If you're curious about some of the technical details for how abrasives are graded in manufacturing, you can read part of this thread (I made a few posts about what I found, but I'm no expert!):

    In particular, have a look at this overview of the offical engineering standards (FEPA, JIS, ANSI). This is from the United Abrasives Manufacturer's Association (UAMA):

    Komitadjie has done a great job with the Grand Unified Grit Chart, but it's really just a very rough road map. You'll have to do some experimentation by yourself to see what works for you, when you switch from one abrasive type/manufacturer to another. If you do, please make a post about it too. :)

    If you find interesting articles or references, please let us know!

    Last edited: Apr 8, 2012
  7. hardheart


    Sep 19, 2001
    Yep, 12K is that particular brands grading, and 2500 would be comparable to another brand, as long as they use the same accepted grit measure. 12K sounds finer, but is meaningless if they are the only ones grading their particles that way.

    As Lagrangian has very clearly explained, the subject is complicated and convoluted. I still start with micron averages, cause heck, we have to start somewhere. It doesn't apply to things like OwE showed with Spyderco ceramics. It's the same for all the sintered ceramic stones, as well as natural stones like Charnley Forests, Arkansas, Japanase naturals, Belgian Coticules, and the rest. Particle size, hardness, shape, and density along with the carrier all play significant roles. But, micron ratings aren't hard to find, micrographs of the abrasive particles along with physical properties and production methods are much tougher to collect for dozens of different stones.

    Even staying with synthetics, you will constantly see things like the Kitayama being stated to cut from 8K to 12K, or the Takenoko 8K and the Arashiyama 6K being the same stone, or the Suehiro Rika graded at 5K cutting like a 3K, and Besters, Green Bricks, Sigma Powers, etc at 700 to 1200 grit cutting faster than coarser DMT plates. Mirror polishes on 1K Choceras and Super Stones while it takes greater than 6K ratings for others to refine the scratch pattern that much.

    Which is also why statements like "it cuts like a 4K" are really meaningless. 4K synthetic stones don't ct like 4K stones, because they all cut differently.
  8. TheBishop


    Aug 27, 2009
    Information Overload! :)
    Lagrangian and Hardheart, you guys have boatloads of knowledge.

    I'm starting to us sanding belts now and have been sticking to mainly 1 - Klingspor up to there 800. Found a smooth transition there in the lineup and then 1200 and 3K Nortons seem to follow up pretty well on getting the scratches gone.
    Then leather strop with Chrom Oxide in .5 seems to do the trick. Gonna add leather and 1 micron Boron before the Chrom Oxide.

    Wish I can find a good supply of around 3 micron paste.

    I went with Klingspor as the full lineup up to 800 is available and want to get comfy with one.

    Now to digest all this info.
    Much Appreciated fellas!
  9. Komitadjie


    May 31, 2011
    Lagrangian has that one spot on. The GUGC is intended to be only a very basic comparison tool between grits, just to give a general idea of how, say, sandpaper stacks up against the JIS number for a waterstone if you want to do that occasional rough profile on sandpaper, then move on to the stones for sharpening, and you need to know which paper is coarser than your 1K. The number of factors that effects how a specific abrasive performs on a specific steel is HUGE, and the micron size is only the beginning of the actual comparison. But for a quantitative comparison, it's the most convenient single number to use, I think, and if you're going to try to set up a chart, simple is good!

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