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Now that I own one...

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  • Now that I own one...

    What do I do with it?

    I bought a 12"X18" precision ground cast iron surface plate. I light polish with a scotchbright and some oil brought it to a glass like finish. The only problem is, I don't know what to use it for. I know this sounds really dumb, but I need some education on this.
    Arbo & Thor (The Junkyard Dog)

  • #2
    Arbo, among other uses, it's perfect for precision layout in conjuction with a height gage. Also, it can be used in conjuction with spotting dye for scraping projects as well. Sorry I can offer more, but my experience is more limited than yours. You might check some of Forrest Addy's posts on scraping for additional insight.

    John B

    Oh yea, I almost forgot, invest in a quality (read Starrett) surface plate cleaner and fabricate some type of cover for it. I used a cardboard target backer to fab a cover for my granite plate.

    John B

    [This message has been edited by jr45acp (edited 07-23-2004).]
    John B


    • #3
      You'll get a lot of information on how to use it, but you'll need some other equipment to fully utalize it like a height gauge, angle block, sine bar, and some sort of presision spacers (gauge blocks, spacer blocks, shaper gauge). Since this is a cast iron plate I'm assuming it's an old one you acuired. If so the first thing you should do is find someone with a good granite plate and ask them to help you check your plate against it with some prussian blue (hi-spot) since cast iron is less stable and durable. When you have it spotted take a picture of the marking so you'll have an idea where the unusable areas are.



      • #4
        I don't know what the old timers will say about it but I personally would never use Scotchbright or any of it's clones on a surface plate. The plate is likely finished to 0.0001 or better and Scotchbright is abrasive. It will take off a little of the surface and it's difficult to predict or control the exact amount without measurement.

        I would use either a commercial surface plate cleaner or just plain soap and water. Dry well with a CLEAN soft cloth.

        I always take care to lightly wipe my plate clean before each use. And I wipe everything that I am going to put on it. This is to avoid scratching with stray grains of abrasive or just plain dirt which is a lot like abrasive.

        If I am wrong on this, someone please chime in.

        Paul A.
        Paul A.
        SE Texas

        Make it fit.
        You can't win and there IS a penalty for trying!


        • #5
          On precision steel / CI surfaces, I use Nevr-Dul wadding and only when absolutely necessary. Also, you want to make sure that you do not focus on a small spot or area but rather, spread out the effort.

          I'd avoid abrasives like the plague because they remove metal and can embed themselves in the surface. The fine grades of scotchbright have silicon carbide as the abrasive.

          I would check it for damage spots (dents and the like) and stone them out with light oil. There are some techniques using very thin shim or paper to prevent a stone from touching the surface except for the dent (until it has been taken down at least).



          • #6
            12" x 18" surface plate perfect!! - I mean. I'm familiar with those particular plates. They're um - radioactive - yeah, that's it. I'm qualified to receive radioactive stuff. Send your new surface plate to me and I'll take care of it - I mean see that it properly enters the contaminated waste site at Handford, WA.

            Trust me.


            • #7
              I am always scared of someone who adds "Trust me" to the end of a statement.
              I think you should send it to me, with shipping prepaid, and I will have it properly disposed of. If Forest is the proper place to dispose of, I will make sure he receives it...
              David from jax
              A serious accident is one that money can't fix.


              • #8
                Cast Iron makes it at least 50 years old. I betcha that it is "way" outta flat but good enough for toolroom inspection. If you ever get another plate, preferably a granite one, you can use the cast iron one for a lapping plate by taping whole sheets of abrasive paper down to it. It works great! We used to use kerosene to clean the adhesive off when changing the paper. If your going to use it as a surface plate, try using rubbing alcohol as it doesn't leave residue. Be VERY careful with it. One of the reasons they stopped using castiron is that when you chip the surface the edge around the chip is higher than the rest of plate.

                EGO partum , proinde EGO sum


                • #9
                  Oooooooh, I bet Evan would like to have that. It would make a great table for his drill press. Come to think of it, I could use that too!