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Thread: Flattening an oilstone

  1. #1
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    Flattening an oilstone

    If I flatten an oilstone on my diamond plate will it dull the plate? Waterstones flatten easily but this old oilstone is going to take some work.

  2. #2
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    Quote Originally Posted by Tom Bender View Post
    If I flatten an oilstone on my diamond plate will it dull the plate? …
    Most likely, yes.

    Is your oilstone visibly out of flat?

    Diamonds may be harder than an oilstone, but the oilstone will still do a job on the diamonds.

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

  3. #3
    Maybe?

    Part of it depends on the diamond plate in question. Also, part of it depends on the lubricant and pressure used. But diamond plates don't last forever. Theoretically, the diamond is orders of magnitude harder than the oil stone, so it shouldn't affect it much. But it'll still have some affect. It shouldn't ruin it, but it'll likely shorten it's lifespan somewhat.

    If you're concerned, you could use sandpaper glued to a piece of plate glass or flat reference or some other abrasive to flatten the oil stone. It'll take longer, but it'll still get the job done. I've used concrete before (my driveway). It'll wear out a spot on your driveway if you just concentrate in one area, but if you spread it around, it seems to work alright. If you're really concerned about flatness, and your old oil stone is severely out of flat, then maybe hit it the concrete to get close, and finish up on the diamond stone to get it perfect. Make some witness marks with a grease pencil and you'll have a good idea of your progress.

  4. #4
    I've done it. Did it dull the diamond plate? Yes, no, maybe?

  5. #5
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    Yes, since it's the binder that holds the diamond particles together that it's going to wear out.

    The easiest and quickest way to flatten an oilstone is to use silicon carbide lapping grit on a piece of float glass and water. It takes only minutes and there's no silica dust to worry about.

  6. #6
    It depends. What kind of oil stone is it?

    Soft Arks flatten slowly on a diamond plate, but generally don't wreck it.
    Crystolon stones flatten fairly quickly and generally don't wreck the plate.
    India stones and hard/translucent Arks flatten super slowly and put a horrible beating on diamond plates.

    What happens is that the diamonds get pulled out of the nickel plating, starting with the tallest/fattest diamonds. The harder/less friable the stone, the faster it wrecks the diamond plate. That's why a diamond plate will flatten water stones nearly forever, but one go at an India stone ruins it.

    I'd rather not wreck my diamond plates, and sandpaper sheets are 8 1/2 x 11" - huge in comparison to a 2x6 or 2x8 diamond plate. Sandpaper also has the advantage that you simply toss the sheet when it slows down.

    My own flattening travails.. I clamp quality ceramic sandpaper onto my surface plate and sanded dry to level the stone, starting with p60 grit. The flattening work happens with P60. Progressive grits simply clean up the scratch marks. I usually stop at p220 except for translucent arks - which go to p600. Replace the paper as soon as the cutting action slows or you'll never finish.

    Crystolon stones are pretty easy - as they flatten by releasing grit, which then speeds up the lapping. Water them good and just keep going until they're flat.

    India stones are tricky, as they are ultra-hard. Flattening with sandpaper tends to glaze them BAD. If an India stone is more than a little out of whack, flattening with 36 grit silicon carbide on a concrete slab is often the only way to make reasonable progress. Then you can move to sandpaper. They'll be completely dead after leveling on sandpaper, though. The next step, once flat is to lap on a true flat surface with loose 80 grit silicon carbide to restore the cutting power. (I clamp a steel cookie sheet to my surface plate for this. Lexan and plate glass both left me with bellied stones.)

    Good luck and tell us how it comes out.
    Last edited by John C Cox; 06-05-2024 at 7:31 PM.

  7. #7
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    Both my father and grandfather used the concrete driveway to flatten their oil stones and it seemed to work OK.
    Chris

    Everything I like is either illegal, immoral or fattening

  8. #8
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    Diamonds are 10 on the Mohs scale, Novaculite or Arkansas stone is 7. To be a black Arkansas stone, it has other minerals in it, but no idea how hard those minerals are. Just for comparison, a steel nail is 6.5. Doesn't seem to me that damage would be done.

  9. #9
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    It's not the diamonds that wear out, it's the substance, whatever that is, nickel plating? That holds the diamonds to the plate that wears out. The diamonds just get knocked out. I don't see any other reason why my once extra coarse diamond stone now it's kind of a fine stone.

  10. #10
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    I remember a thread years ago about this topic.
    George Wilson suggested using a potters wheel to lap oil stones flat. Another suggestion was a cinder block from the borg.
    I have personally ruined a diamond plate trying to flatten a translucent Norton stone.
    The potters wheel suggestion is something Id like to try someday.
    Good Luck
    Aj

  11. #11
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    I use silicone carbide grit with oil on a granite countertop off cut. Works great and fast.

  12. #12
    I've done really bad flea-market finds on the surface grinder.
    It is fast for flat, but then you need to roughen them up to expose sharp grit.
    The diamond abrasive simply smooths off the top of the exposed grit.

    Per other notes, translucent Arkansas is surprisingly resistant to grinding even with a diamond wheel.
    I'd probably not try that one again. Or maybe use a much coarser wheel, faster traverse & infeeds, and smaller downfeeds.

    But of stones of my own in regular use, i've never needed to flatten one.
    Just use the stones all over. Not all are flat, but i keep them trending that direction. With most applications, focus on trying to make it convex. Use any developing high spots as an welcome option to aggressively counter-cut high areas in the center of plane irons and wide chisels, etc.

  13. #13
    When I needed to flatten a hard Arkansas stone I sent it to Dan's. It was cheap and they sent it back dead flat. Before I sent it out I killed one DMT X-Coarse. Never again.

  14. #14
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    The few times I've ever flattened a Washita or a Soft Arkansas I used an old window pane on top of a cinder block out in the yard with Carborundum grit. I forget what the grade of grit was, but it was some I had left over from grinding telescope mirrors when I was a teenager. It was pretty coarse though, so probably one of the starting grits. Just like grinding the glass mirrors, you make a slurry with a little bit of water.

    Diamond stones don't last as long as it seems like they should, so I wouldn't use one for this purpose. Water stones are much easier to flatten.

  15. #15
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    Diamond stones don't last as long as it seems like they should, so I wouldn't use one for this purpose. Water stones are much easier to flatten.
    Both diamond stones and water stones are friable. Arkansas stones are much less friable.

    The big difference is diamond stones are not a matrix of diamonds. They are a layer of diamonds bonded to steel. Water stones friability works with the surface of a water stone to abrade and polish. On a diamond stone, they will also work until they fall off of the plate. The diamonds become less aggressive over time.

    In materials science, friability, the condition of being friable, describes the tendency of a solid substance to break into smaller pieces under stress or contact, especially by rubbing.
    This is why diamond stones seem to become finer with use. An Arkansas stone has a similar fate, only slower.

    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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