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Cutting a DRO glass scale

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  • Cutting a DRO glass scale

    As mentioned in another thread, I needed to cut a Mitutoyo DRO scale down to fit on the long axis of my mill. Obviously a fairly nervous business, a couple of hundred pounds (sterling) down the pan if it goes wrong.
    I'd given the options some thought for a while, it's not just a straight cut because the aluminium body is cut with a step for the end block.
    The option I went for in the end was to use a hand-held 5" angle grinder with a thin (1mm) cutting disc, the ordinary ones sold for cutting steel, usually labelled as for stainless. Did some experiments with bits of Ali and shards of ordinary window glass which convinced me that nothing really nasty was likely to happen, though obviously the discs are not intended for cutting either aluminium or glass. The glass shards would break after a moments grinding, not exactly on the line of the grind but not in a completely unpredictable way, so after the experiments I went for the real thing.
    There was about 10" to cut off, so I started by cutting an inch or so off the end of the scale to see what happened, reasoning that my tests had shown that the whole scale wasn't likely to shatter and if this cut was a mess I could still try other ways for the 'real thing'. Test was OK, so I marked off for two cuts 10mm apart for the step. Again I was playing a bit safe by cutting to almost the full length of the mill table, which would allow spare for a second attempt if it went wrong without actually shattering the scale. Cutting ali with a grinding disc produces a fair bit of heat, an extra reason for going very gently.
    In fact, the whole thing was remarkably painless, of course the extrusion needed a bit of filing to tidy up and then drilling for the end block, and I filed the end of the scale back a bit with a diamond file as well as smoothing the edges, so that the end block would not be putting pressure on the end of the glass.
    A good blow through with compressed air, refit the reader head and fit the end blocks with a dab of silicone, and all appears OK.
    Please don't shout at me if you use this method and it goes wrong

    Tim

  • #2
    I have tried to cut glass with a diamond blade for concrete and it went badly wrong with the glass shattering. I suspect that a tile-cutter disk which has much finer diamond powder on it would make a good job. Never tried it with a carbon blade.
    For extra protection of the glass scale I'd be tempted to sandwich it between two pieces of something that the disk will cut, to help prevent it shattering. Good idea to do some test-cuts on the end first.
    Peter - novice home machinist, modern motorcycle enthusiast.

    Denford Viceroy 280 Synchro (11 x 24)
    Herbert 0V adapted to R8 by 'Sir John'.
    Monarch 10EE 1942

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    • #3
      Great Job, Glad it worked. Sounds like a tedious afternoon. Fred

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      • #4
        Originally posted by laddy
        .... Sounds like a tedious afternoon. Fred
        Not really, probably spent 1 to 1.5 hours start to finish, including test cuts and putting it back together. Fitting to the machine will take longer, it's a beautiful spring day here, far too nice for (optional) workshop time so that'll have to wait.

        Tim

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        • #5
          I would have thought that the glass scales were tempered and would have shattered the entire scale even if you tried to "nip" @ the end of one,
          you pioneered a new option (or at least an option for your brand of scale )

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          • #6
            Originally posted by A.K. Boomer
            I would have thought that the glass scales were tempered and would have shattered the entire scale even if you tried to "nip" @ the end of one,
            you pioneered a new option (or at least an option for your brand of scale )
            My old mill had an old model of Heidenhain DRO, I gave up with it after problems first with the counter and then one of the scales, it seems that those particular scales have a life span & they were all dying at about the same age so no replacements available.
            After I'd abandoned using it, the glass in the long scale broke presumably after a mechanical shock. It broke into 3 or 4 pieces, no sign of shattering there.

            Tim

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            • #7
              My wife and I dabble a little in Stained Glass and we purchased a diamond ring saw that is used to cut glass like a band saw. I think if someone was to try what Tim did with his glass scale, it would be wise to locate a stained glass shop and see if they would be willing to attempt the cut. Glass seems to not follow the rules when it come to cutting.
              Glad to see that you had success Tim, but really think you got lucky.
              Mel
              _____________________________________________

              I would rather have tools that I never use, than not have a tool I need.
              Oregon Coast

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              • #8
                A quick update, got the newly cut scale mounted & tested on the machine today, all seems fine. Short scale next, that one is exactly the right length already.
                I mentioned somewhere that I fancied getting a 3-axis setup but they're out of my budget at present. I've got an old Anilam Wizard 2-axis kit which I'm thinking of fitting as a dual Z-axis readout, one scale on the knee and the other on the quill. I'm undecided at the moment, it's more work when I've got other things to get on with, & the machine will end up like a Christmas tree with scales & cables everywhere, including the VFD in an enclosure bolted to the top of the overarm
                Anyone done this sort of thing?

                Tim

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                • #9
                  Originally posted by Timleech
                  the machine will end up like a Christmas tree with scales & cables everywhere, including the VFD in an enclosure bolted to the top of the overarm

                  Anyone done this sort of thing?

                  Tim
                  Wot ? made a Christmas tree ?

                  .
                  .

                  Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                  • #10
                    Originally posted by John Stevenson
                    Wot ? made a Christmas tree ?

                    .
                    Ho Ho Ho

                    Fitted two 2-axis DROs onto a mill, and if so was it worth the effort?

                    Tim

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                    • #11
                      One of the guys on another list has a two axis on a lathe and a further 2 axis setup with the scales on the compound and tailstock.

                      seems to work for him but then again he doesn't go out much as he doesn't know where magnetic north is

                      .
                      .

                      Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                      • #12
                        I am just wondering why you didn't buy a scale the appropriate size???
                        Precision takes time.

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                        • #13
                          Originally posted by Ringer
                          I am just wondering why you didn't buy a scale the appropriate size???
                          Simple. I already had the longer scale, a new one the right length would have been of the order of £200/$300US or more (ball park ). Selling the one I had would have been uncertain.

                          Tim

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                          • #14
                            ahhh OK...
                            Precision takes time.

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