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  1. #1
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    Default Flattening a cast iron plate

    Hello, I am flattening a couple of cast iron plates 63 x 200 surface dimensions. I have tried, over several hours, 80 grit W&D on glass, 80 grit of a belt sander belt on glass, and the Extra Coarse side of a DMT DuoSharp diamond plate, as used to rapidly repair damaged or real rough edge. (220 mesh, 60 mircron), without getting too far, as shown in the attached photos below

    Can anyone please suggest a better way of flattening these plates, to a surface finish much the same as using 320 grit W&D?

    All suggestions and ideas gratefully received

    P1690269 (Large).jpg P1690270 (Large).jpg
    regards,

    Dengy

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  3. #2
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    Without having access to a surface grinder pretty much W&D is your only real option. One thing that might help would be a wooden carrier with a handle so you can really bear down when rubbing over the W&D. I made a surface plate a couple of decades ago using the traditional methods of filing and scraping with a reference surface but that is a whole different skill set to learn.

    You could go on the Metalworking Forum and ask if someone would be willing to grind them flat but naturally there would be a cost involved; it will be much cheaper than asking a local engineering shop to do it though.

    Are they for sharpening with diamond lapping pastes or something totally different?
    Nothing succeeds like a budgie without a beak.

  4. #3
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    Are they for sharpening with diamond lapping paste ?
    Yep, was intending to try it out and see how it goes for for me honing chisels after hollow grinding. I like the idea of being able to hone them by hand quickly without using a jig. I have been using hard leather and more recently, hardwood, with the green polishing compound from Polish Up. Looking to try out an AutoSol car polishing paste too

    Thanks for this reply, Chief. I use the magnetic stand from my dial gauge setup to grip the plates and it allows me to use downward pressure, although not evenly spread over the whole length of the plate.

  5. #4
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    Thanks for the tip about using a surface grinder. Found our local blade sharpener had one, and would flatten both sides of the cast iron plates for $15 each. He said they would have a glass finish. Looking forward to getting them done
    regards,

    Dengy

  6. #5
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    That's an excellent outcome and sounds pretty darn cheap also. Looking forward to the photos...
    Nothing succeeds like a budgie without a beak.

  7. #6
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    Way to go.

    If approaching that with some kind of powered setup I would rough them out on a linisher (the Sorby ProEdge in my case) or even Worksharp discs mounted on an arbour in a lathe or drill press.

    Lapping can be done manually. Just takes time . I did a #8 plane base once. Loose 80 grit SiC grains on plate glass is probably the best option. That starts to work when the glass becomes abraded enough to hold the grains. Use kero for lubrication and regularly wipe off the abraded metal and broken grains.
    Cheers, Ern

  8. #7
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    BTW one alternative to DIY cast iron plates is solid diamond plates at end of their life.
    Cheers, Ern

  9. #8
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    Start with 80m grit trizact belt glued to glass. This lasts longer and cuts better. Then move to a 120 grit trizact belt. After this you can use wet and dry. Wet and dry does not last long enough in the low grits to do the work you want.

    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.

  10. #9
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    Glued sheet abrasive leads to the corners getting overworked.

    When rehabbing a chisel or plane blade you can leave the bevel till last and then grind the drop-offs away.

    When metal workers need a flat surface by hand they scrape or lap. They don't sand.
    Cheers, Ern

  11. #10
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    Hi Ern

    The issue with the corners is down to technique, don't you think? How one centralises down force is very important. Do not "wipe" the plate back-and-forth. I have had very good results, with no dubbing I can measure (good enough for the purpose). Certainly, scraping can bring a higher level of flatness. This may be done at the end, if needed. Do you find scraping faster than sanding?

    Regards from Perth

    Derek
    Visit www.inthewoodshop.com for tutorials on constructing handtools, handtool reviews, and my trials and tribulations with furniture builds.

  12. #11
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    I never got past it I'm afraid. Tried figures of 8. It also happened with the WorkSharp discs and the ProEdge linisher but to a lesser extent. My generalisation was that the leading edge gets more abraded than the trailing. My speculation was that sheet abrasive allows some compression and some stretching and bunching - very minor but over thousands of strokes...

    As for scraping, with the kind help of forum members I got kitted up to do it but ran out of motivation.
    Cheers, Ern

  13. #12
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    Quote Originally Posted by Dengue View Post
    Hello, I am flattening a couple of cast iron plates 63 x 200 surface dimensions. I have tried, over several hours, 80 grit W&D on glass, 80 grit of a belt sander belt on glass, and the Extra Coarse side of a DMT DuoSharp diamond plate, as used to rapidly repair damaged or real rough edge. (220 mesh, 60 mircron), without getting too far, as shown in the attached photos below

    Can anyone please suggest a better way of flattening these plates, to a surface finish much the same as using 320 grit W&D?

    All suggestions and ideas gratefully received

    P1690269 (Large).jpg P1690270 (Large).jpg
    If you dont mind me asking where did you get the cast iron. I am considering trting this method out as i am sick of the mess from water stones.
    Thanks

    Stuart

    Sent from my SM-G930F using Tapatalk

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