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  • New (to me) Mill

    Hello, I'm new here and this looks like a good place to learn alot of stuff about machining. I have a question about a mill I just got. How good is good enough? I mounted a guage to test any variance in the table and moved the table front to back and side to side and the table only varied from 0.0000 to 0.0015...In my mind, that's good..but then again, I'm no machinist! Any thoughts?

  • #2
    {{How good is good enough? }} One of the great questions of all time. Search the archives for checking the spindle, table, and everything under the sun. What kind, size is it? Welcome!

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    • #3
      "It all depends." What are you trying to do? Quite likely the accuracy you have will be "good enough" for most anything you're likely to tackle...but only you can know for sure.

      There's also the "knowing your machinery" aspect of things. If you know the quirks of your milling machine, and what you need to watch out for, you'll be able to get better work out of it than one might anticipate.
      ----------
      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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      • #4
        .0015 error sounds very good to me.

        How's the tram of the spindle to table?

        That means mounting an indicator in the spindle
        and sweeping the table with the indicator.

        A good machinist learns to compensate for errors
        and make parts better than his machine.

        If you're making rocket parts, your .0015" may
        not be good enough.

        For most work, that will be fine.

        Kap

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        • #5
          Kindest regards from over the pond and a hearty welcome Alistair
          Please excuse my typing as I have a form of parkinsons disease

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          • #6
            Originally posted by KMB
            I mounted a guage to test any variance in the table and moved the table front to back and side to side and the table only varied from 0.0000 to 0.0015...
            The test you did measures the local flatness of your table, and your numbers are fine if you're just getting started.

            Eventually you'll want to check/adjust the "tram" -- how perpendicular the spindle is to the table, but that's a relatively involved process.

            For now, I'd just make stuff. You'll know if you have a problem with the machine alignment. Then post your question here -- you'll find a ton of people willing to help you.

            Have fun, be safe!

            Cheers,

            Robert
            "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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            • #7
              Originally posted by kap pullen
              .0015 error sounds very good to me.

              How's the tram of the spindle to table?

              That means mounting an indicator in the spindle
              and sweeping the table with the indicator.

              A good machinist learns to compensate for errors
              and make parts better than his machine.

              If you're making rocket parts, your .0015" may
              not be good enough.

              For most work, that will be fine.

              Kap
              That's exactly what I did! I figured it would be a good test for it. I'm making motorcycle and lighting parts, no rockets here!

              The mill is an old Maxmill YC-1-1/2VA (Bridgeport Clone)...I can't remember the table size, somwhere around 9x50 I want to say...here is a pic of the same one: http://machinetoolsforsale.com/Pictu...Mill_Vmill.jpg

              I've done some test cuts with aluminum, and I'm very excited about using it.

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              • #8
                Originally posted by KMB
                I mounted a guage to test any variance in the table and moved the table front to back and side to side
                ...
                Originally posted by KMB
                Originally posted by Kap
                That means mounting an indicator in the spindle and sweeping the table with the indicator.
                That's exactly what I did!
                To test the tram of a mill, the table doesn't move: you mount a DTI on a horizontal rod like a Zero-It indicator holder, and sweep the DTI in a circle around the table. You'll have tram errors at each point on the clock face. You then adjust the front/back, and left-right "lean" of the spindle to minimize the tram error, which results in the spindle being perpendicular to the table.

                What I was implying by "just start making stuff" is that you'll typically see tram errors when you take wide parallel cuts across a flat workpiece -- there will be a ridge between each subsequent pass. If you're not seeing any problems with this, then you don't really need to adjust the tram yet.
                "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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