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Thread: Diamond plate rougher than oil stone?

  1. #1
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    Diamond plate rougher than oil stone?

    This is not a war on oil vs water vs diamond stones. Merely an observation.

    While at a friends shop he was showing me his diamond stones he uses to sharpen his knives. He also has a few wood chisels he hasnt sharpened and asked if i would show him what i do. While flattening the back of the first chisel, i noticed that even the 600 grit plate was leaving deeper scratches than my oilstone that is advertised as 320 grit. We were using glass cleaner as a lubricant.

    Now his diamond stone isnt anything high end, and that may have a lot to do with it, but does anyone know why this is?

    I guess i have a theory that maybe as my oilstone has worn down it has become finer, and the metal particles suspended in the oil act as maybe a polishing compound similar to a waterstone?

    Anyway, it was an interesting observation.
    Last edited by Jason Buresh; 11-16-2020 at 3:33 PM.

  2. #2
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    Don't definitively know, but some thoughts:

    1- there are many grit scales and not every product, or class of products, use the same one. (E.g. sandpaper doesn't track with waterstones.)

    2- IIRC- grit is an average size and every product has more or less variation from that standard.

    3- (It's rumored) some sharpening stone lines include a little "marketing spin" in their grit ratings.

    4- different abrasives cut the metal with different profiles. Diamond is especially harsh, cutting deeper and creating steeper sided scratches.

    In short, YMMV!

  3. #3
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    One thing might be is diamond plates is NOT worn. The diamond hones, like diamond and CBN wheels, need a some "break in" time to knock the tops off random higher grit particles.

    I haven't paid much attention to the grit vs finish. I keep diamond honing plates from 180 to 1200 grit and reach for a coarser or finer one as needed.

  4. #4
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    my oilstone that is advertised as 320 grit
    The advertisement is marketing nonsense. Oilstones do not have a grit size since they are formed by natural process. Diamonds, abrasive sheets and man made water stones are made with materials that have been screened or measured in some other way to gauge their grit size.

    Man made oilstones may have some relationship to grit size. Usually Crystolon, India and others are labeled coarse, medium and fine.

    Natural oilstones have a few different ratings depending on who is selling them. Washita, soft, hard, translucent and black are common but will have some variance depending on the mine or the vendor.

    Good luck finding a genuine Washita.

    On a diamond stone deep scratches may be caused by a few 'rouge' diamonds on the plate. If you go back and forth 100 times one 'rouge' diamond can leave 100 deep scratches.

    As David posted:

    2- IIRC- grit is an average size and every product has more or less variation from that standard.

    3- (It's rumored) some sharpening stone lines include a little "marketing spin" in their grit ratings.
    One maker's 6000 water stone may be a finer grit than another's 8000 grit water stone.

    Here is something to make it more confusing:

    Abrrasive Grit Chart 2019.jpg

    jtk
    Last edited by Jim Koepke; 11-16-2020 at 4:19 PM.
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  5. #5
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    If the plate has a pattern of diamond (like my Atoma), repeated passes in the same direction will leave an obvious scoring "line".

    Some diamond plates cut steel, fast.

  6. #6
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    This has a pretty good write-up

    https://www.bestsharpeningstones.com...ng-stone-grits

    They are basing things on scratch patterns and their "Soft Arkansas" they list as a grit equivalent to 1200. Everyone does it differently, but, I need to run, so quickly, look hre as well.


    https://www.danswhetstone.com/inform...ne-grades-101/

    Sorry, typing slowly, saw + hand and saw wins, sorry finger, will post about that later.

  7. #7
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    And now you understand WHY I hate working on a Monday....

  8. #8
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    Quote Originally Posted by steven c newman View Post
    And now you understand WHY I hate working on a Monday....
    Cut the finger Friday evening. Oops! Was cutting a box apart with my dovetail saw and it "let loose". Should not have been holding the box by hand.

  9. #9
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    I made some assumptions when I read this. My first assumption was that your oil stone was an Arkansas stone. Bad me!

    Arkansas stones are notoriously "fine" so that is one thing. If your stone is really labeled as you say, then I assume that it is NOT an Arkansas stone, so it is probably manufactured. My experience with this type of stone (India and Crystolon, for example) is that they are very uniform. I do have some manufactured stones that are not as uniform, however; for example, the American Mutt stone by Byxco, but they use water, not oil, and they are not the least bit flat (I would say sadly, but not sure it matters for this stone) and very coarse.

    If you run a blade along the stone, does it catch? I had a stone from DMT that had a few areas that would catch and I just could not seem to wear it down. I finally just ran some metal strongly enough to knock those bits out. I could not see them under a 20X magnifier, but they sure caught my blades. I expect them to need some wear in, but this is typical.

    Also note that some people swear that you should not use diamonds because they will (or can) leave deep trenches that are really hard to remove. I also know people who shake there head at that and only use diamond. Also, some brands are more likely to show this than others, especially "lower quality" brands, whatever that means. I would try to wear it in and see if it makes a difference. If you are not sure how to wear in a diamond plate, just holler, my hands are getting tired so I will stop typing now.

    I rarely do my final polish on a diamond, even if I do have some very fine diamond plates. For the record, some people prefer the rougher edge along the edge, but I usually hear that in the context of a knife depending on what it will cut; for example, a less smooth edge is often better for cutting rope.

  10. #10
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    for example, a less smooth edge is often better for cutting rope.
    This is fine for using a knife to saw rope.

    With a fine edge my old Boker poket knife will cut through rope by setting it on a piece of rope and pushing down on it. No sawing motion needed.

    For larger knives one of the knife making programs demonstrated sharpness by cutting a piece of free hanging rope by swinging the blade at it and cutting it with one blow.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

  11. #11
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    My main plates are DMT since I don't have running water in my shop. The waterstone users are generally quite enthusiastic about their systems, but not an option for me currently.

    While I am satisifed with my DMT plates (300,600,1200,4000), my next plate will probably be an Atoma@ 240 because of my insatiable rust hunting.

    I have quite a few lesser names in smaller diamond products, knife sharpeners and field kits and so on, and the cheap stuff just doesn't measure up. I am not even particularly pleased with my perforated? DMT suff. The flat plates with uniform stones on them are good. The ones of sheet metal tops with holes punched and islands of diamond media are for your utility knife while moose hunting 20+ miles from the nearest paved road, or hatchet; not for your skinning knife in the field and I don't use them in the shop for anything if I can help it.

    It is my personal experience that the price of a diamond stone from a well regarded manufacturer is a good indication of ultimate edge quality achievable. If I was 40 years younger, which I haven't been for 40 years, I might argue with myself about that. The younger me would have (did have) better eye sight and better hand/eye coordination and could do all manner of things I can't do anymore.

    M2c

  12. #12
    Diamond plate rougher than oil stone?

    Short answer: Yes they are.

    Somewhat longer answer: It is a factor of the shape of the cutting grit. Diamonds and for that matter most man made stones leave deep straight sided scratches where a natural stone's scratches are not as deep and have more rounded sides. Straight sided scratches are great for "shine" but not as good for edge retention. That's getting too deep into the sharpening weeds but bottom line almost any stone will give a sharp edge, some will end up with a smoother cutting edge which in turn should last longer.

    ken

  13. #13
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    Thank you everyone for the helpful information. It makes me glad I found a sharpening system that works for me and I stuck with it.

    Jim, that chart is a weapon of mass confusion

  14. #14
    Diamond plates often have some diamonds that are large and stick up considerably higher than the other diamonds.

    Here's a picture of a DMT extra-fine plate, from this post on the Science of Sharp blog. There's a huge diamond in the middle of all the other small ones.

    dmt_1200_new_3_04.jpg

    According to that blog post, some of the large diamonds will fall out after a break-in period, but some will remain. Eventually these diamonds will wear down or fall out, but it can take a long time.

    I've had DMT plates and currently have a Trend diamond plate that initially left deep scratches but then got better over time. My understanding is that Atomas have more consistent sizing, although I've never actually used one before.

  15. #15
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    While I am satisifed with my DMT plates (300,600,1200,4000), my next plate will probably be an Atoma@ 240 because of my insatiable rust hunting.
    For me a four inch wide roll of 220 abrasive paper with an adhesive backing mounted on a long piece of granite works great for handling/removing rust.

    jtk
    "A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
    - Sir Winston Churchill (1874-1965)

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