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  • Stoning a Mill Table?

    As a final touch to the renovation of my mill, I have been advised by a friend to go over the top surface of the table with a pair of bar type sharpening stones. The approach would be to use two stones, each being as long in dimension as I can afford. The stones would be rubbed together first, and periodically thereafter to assure that they are both planar. They would then be used to very lightly stone down the raised portions of the ding marks on the table. Of course, best possible care would be taken to assure that only the raised defects were being reduced.

    Would attempting this be advisable, or insane? If the approach is sound, what type and grade of stone should I use? Any advice would be much appreciated.

  • #2
    Well, rubbing together two rectangular stones does not ensure they are flat; one could be concave and the other convex, to match. To generate a plane you need 3 square plates (or stones) that are matched each-to-each at 0 and 90 degrees.

    I'd just use a single stone, and not worry about it.
    ----------
    Try to make a living, not a killing. -- Utah Phillips
    Don't believe everything you know. -- Bumper sticker
    Everybody is ignorant, only on different subjects. -- Will Rogers
    There are lots of people who mistake their imagination for their memory. - Josh Billings
    Law of Logical Argument - Anything is possible if you don't know what you are talking about.
    Don't own anything you have to feed or paint. - Hood River Blackie

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    • #3
      I stone mine whenever needed (which is to say whenever anything hard or heavy dings it). I've never seen this procedure anywhere but it works well for me.

      Clean the table surface as well as possible. Give it a final wipe with a paper towel dipped in acetone/laquer thinner. Spray the entire surface with WD-40. Your stone will "float" on the oil film and only contact the high spots. If you wear an OptiVisor, you'll see bright reflections as any dings are ground down.

      If you can feel the stone on the table, either the stone is not fine enough or the oil film is not heavy enough. I use a white, hard Arkansas stone that's 1" x 3" x 1/4" thick. I would not use anything coarser than that. There's also a black, hard Arkansas but it is super fine. You could probably use a fine ceramic stone as well.

      Check the table with a straightedge of known accuracy. I use a Starrett that's accurate to .0002" per foot. J&L currently has this on sale if you need one. Their item # is STC-51470J.

      ------------------
      Barry Milton
      Barry Milton

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      • #4
        my vote's for insane.

        Its confusing two problems and their corresponding techniques, 1) removing dings and 2) getting a surface flat.

        a small fine Arkansas stone will find and correct the dings. another technique is break off a 2-3" piece of a worn out fine file - this is especially useful for removing any burns that might have been left by scraping. Regardless, finding and correcting a ding or burr does not require a large stone, in fact that might impede the job. with the small stone you can feel when you hit a burr.

        rubbing the stones together is sounds more like a misguided attempt at trying to get them flat and subsequently impart said flatness onto your table. If this is the objective, you need to work from a reference surface, using blue to identify high spots and then remove them with a scraper

        oops, i'm a slower typer than Barry - i think we're both saying the same thing. another thing that scares me about that advice is "getting the longest stones you can find" the Arkansas types we're talking about are very fine and almost have a polishing action, and are usually pretty small in size. I' hate to see you take some big oil or water stone to it!

        [This message has been edited by Mcgyver (edited 04-27-2005).]
        .

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        • #5
          Make sure the table is well lighted, and angle your head at the right angle so you can clearly see the fine scratches the stone is making.This way you can move along when you see that you have removed the high spot and are rubbing across the whole surface of the stone.I always go over the table completly from one end to the other. In theory I am wearing the table "straight down". If you just stone the middle, where the dings usually are,you will create a low spot after 30 or 40 years

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          • #6
            I use a stone shaped like a hockey puck with a big finger groove in the centre. Works great on all surfaces die blocks. Circular pattern not too much pressure. i find i can feel the burrs as i pass the stone lightly over the surface,. Then a couple os swipes burrs gone. Too much spirited stoning will remove too much material.

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            • #7
              You can "wear out" your own file for the purpose.....

              Stone a convenient sized piece of file until you see flats on top of the teeth. Do both sides. I like a piece a bit over an inch wide, and maybe 3 long.

              Now you have a "burr file".

              It won't cut any flat surface, but it knocks down stuff that sticks up. It will do a good job on your mill table.

              I use one between scraping cycles to knock off the "fuzz". You can feel it quit cutting the stuff that sticks up, and start to just skate around.
              1601

              Keep eye on ball.
              Hashim Khan

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              • #8
                I can grasp most of the thread but At this point, I am preparing copies of such scraping articles as I have to Hood- who is doing up a Bridgeport.The Connolly book isn't available in the UK.

                Having got to the stage where scraping cycles reach a point where the surface is flat- but still unfinished, J Tiers suggests a worn or dumbed down file.
                I appreciate why- and that is to remove the small ridges left by successive scrapings.These would show up in a blueing.
                The file suggested is not clear. Could you expand the details, please? I was thinking of size, shape, teeth etc.

                Thanks

                Norman Atkinson

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                • #9
                  When I started rebuilding my old JET mill-drill last year, I realized just how beat-up the table was. No drill-throughs or mill marks, just a bunch of very fine dings from setting tools down, or dropping a hold-down clamp, etc.

                  I got the mill used, with some tiny dings, but I never noticed just how many more I'd added over the years from setting down a wrench or piling clamps or setting 123 blocks down carelessly.

                  I took a small stone- only one I had, I use it for honing lathe tools- and used WD 40 as a lube. I'd squirt a small area, then rub the small triangular stone (on a flat) in an errattic circular and figure-8 pattern. Once I couldn't feel it "grabbing" at the peaks, I moved to the next spot.

                  It made a huge difference in appearance and smoothness.

                  If you're doing it yearly, yeah, you'd need to worry about eventual material removal. If it's a once-a-decade thing, just hit it with the stone and some light oil until you can't feel it catch a burr anymore, then call it good. Don't worry about stoning it down to an even finish or uniform appearance.

                  Doc.
                  Doc's Machine. (Probably not what you expect.)

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                  • #10
                    Thank you, Doc for the time and trouble.
                    I suppose that my mill drill is from the same source but sports a different label.
                    I was actually more moving towards a somewhat ancient 31/2" Myford lathe of doubtful parentage.

                    I got a present- or nearly of another lathe set of castings- to make a straight edge
                    ( well!!).

                    As predictions for the future are not in 10 year cycles but reading the morning obituary column before getting up, I a limiting my enthusiasm to one job at a time- or even getting up.

                    Thanks, once more.

                    Norman

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                    • #11
                      <font face="Verdana, Arial" size="2">Originally posted by madman:
                      I use a stone shaped like a hockey puck with a big finger groove in the centre. Works great on all surfaces die blocks. Circular pattern not too much pressure. i find i can feel the burrs as i pass the stone lightly over the surface,. Then a couple os swipes burrs gone. Too much spirited stoning will remove too much material. </font>
                      I have the same stone and use it before I put my vise back on. I store it in a 50-50 mix of motor oil and kerosene in a old coffee can.

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                      • #12
                        Hi guys I've asked before about this
                        is there any chance i could stone my table with this..pic below
                        The stone part of it is about 4 inches in diameter..having to move the ram on the turret between goes.
                        doing one half of the table overlaped at a time (bridgeport).
                        surly this mounted in the spindsle and with plenty of lube and spun at the fastest rpm it will do a good job.
                        will true the stone first with a diamond mounted on the table.
                        or do you see it otherwise





                        all the best..mark

                        Comment


                        • #13
                          Mark,

                          You are a brave man to think about doing this. Before you do, check surface flatness with a reliable straightedge (see previous post). I'd bet that an older BP, where all the surfaces were handscraped or ground, will be very close to flat, probably less than .0005".

                          Even if the table is in terrible condition, I wouldn't try the method you mention. There are many places that refurbish BP's, and they have the tools & equipment to reflatten the table. It is an operation best done on a large Blanchard-type grinder.

                          ------------------
                          Barry Milton
                          Barry Milton

                          Comment


                          • #14
                            <font face="Verdana, Arial" size="2">Originally posted by aboard_epsilon:
                            Hi guys I've asked before about this
                            is there any chance i could stone my table with this..pic below
                            The stone part of it is about 4 inches in diameter..having to move the ram on the turret between goes.
                            doing one half of the table overlaped at a time (bridgeport).
                            surly this mounted in the spindsle and with plenty of lube and spun at the fastest rpm it will do a good job.
                            will true the stone first with a diamond mounted on the table.
                            or do you see it otherwise

                            all the best..mark
                            </font>

                            Please dont do this to your bridgeport.

                            Comment


                            • #15
                              Not quite hijacking the thread....

                              Norman:

                              Burr file made as mentioned....is a detail cleanup tool, not for accomplishing ANY serious surface metal removal during scraping OR de-dinging a surface.

                              Because the sharp tips are flattened slightly, it glides nearly harmlessly over a flat surface. Almost like sliding a flat plate.

                              I like a busted piece of single-cut file, with smooth or ground-off edges.

                              It is NOT for finishing the surface....it is only for removing "fuzz" after scraping the surface over, before wiping and spotting. Lightly moved around until it glides.

                              You can use a fine stone. I did, but they gummed up too fast. And it was hard to tell what was "enough". So the file came into use. Connoley mentions them.

                              Will do a really good job removing dings. Anything that sticks up. As soon as the surface is flat, it just glides without resistance.

                              About that grinding..........
                              If you use the mill to mill or grind the table, does that not simply reproduce the problems of the saddle in the table? And the worn spots of the table guiding surfaces?

                              Sounds like a very bad idea, frankly.

                              If the table were supported on parallels by its guiding surfaces, and they were known flat and coplanar, presumably the top could be ground on a surface grinder.....or planed, etc with the knowlege that it was parallel with the guiding surface.

                              [This message has been edited by J Tiers (edited 04-27-2005).]
                              1601

                              Keep eye on ball.
                              Hashim Khan

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