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Mill tolerances

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  • redbaron192redbaron192
    Hi, I have just brought a new Amadeal X12-300 mini mill (seems to be identical to the mills sold by Big Dog) to replace an old mill that i started off with
    Message 1 of 3 , Apr 28, 2010
      Hi,

      I have just brought a new Amadeal X12-300 mini mill (seems to be identical to the mills sold by Big Dog) to replace an old mill that i started off with about 4 years ago.

      http://www.bigdogmetalworks.com/productcart/pc/viewPrd.asp?idcategory=16&idproduct=781

      I have just milled a test block of aluminum, measuring approx 70mm in the X axis, and 40mm in the Y axis.

      Measuring it with my calipers, and looking at it with a set square, it looks like it is about 0.04mm out of parallel.

      I have checked my vise, and found it is slightly out of parallel by just less than 0.01mm. Checking the table, i find over the entire X axis movement, the Y axis has a variance (depending on the table position) of between 0 to 0.02mm (measured with dial gauge in a locked head).

      Adding these errors up, my test block appears to reflect the potential total variance.

      What tolerance should i be aiming for, or can expect to achieve assuming I can improve the table accuracy?
    • i_r_engineer
      My experience is similar to yours with my Cummins X2. On a block about 3x2x1 I can hold about 0.002-0.003 relative to square and parallel when using my
      Message 2 of 3 , May 3, 2010
        My experience is similar to yours with my Cummins X2. On a block about 3x2x1" I can hold about 0.002-0.003" relative to square and parallel when using my vise.

        The main source of error for me seems to be in tramming the mill at different z heights. To fully tram the mill at all heights requires to first square the column and then tram in the head. The column is easy side to side but must be shimmed front to back. The head has no easy adjustments.

        For me, the .002" is good enough for 99.9% of the work I do. If I need better, I will be doing it by lapping etc.

        Jerry

        >
        > Measuring it with my calipers, and looking at it with a set square, it looks like it is about 0.04mm out of parallel.
        >
        >
        > What tolerance should i be aiming for, or can expect to achieve assuming I can improve the table accuracy?
        >
      • redbaron192redbaron192
        I ve just finished stripping down the upper part of the Mill - its fairly easy to take apart, and started by lapping the slides on the column mount for the
        Message 3 of 3 , May 12, 2010
          I've just finished stripping down the upper part of the Mill - its fairly easy to take apart, and started by lapping the slides on the column mount for the head. I then aligned the spindle to the ways using RDM as seen on a webpage somewhere, so now I am fairly confident the spindle is parallel to the column.

          Whilst it was apart, I packed out the rack with a few sheets of aluminum foil to reduce the play in the gear of the head movement mechanism.

          I've yet to mill my test block again - i am not expecting to see any improvement as the above tends to fix the kind of problem you describe. I am partly through making a bracket for fixing the top of the column to the back wall of my garage to reduce flexing of the column.


          --- In GrizHFMinimill@yahoogroups.com, "i_r_engineer" <i_r_engineer@...> wrote:
          >
          > My experience is similar to yours with my Cummins X2. On a block about 3x2x1" I can hold about 0.002-0.003" relative to square and parallel when using my vise.
          >
          > The main source of error for me seems to be in tramming the mill at different z heights. To fully tram the mill at all heights requires to first square the column and then tram in the head. The column is easy side to side but must be shimmed front to back. The head has no easy adjustments.
          >
          > For me, the .002" is good enough for 99.9% of the work I do. If I need better, I will be doing it by lapping etc.
          >
          > Jerry
          >
          > >
          > > Measuring it with my calipers, and looking at it with a set square, it looks like it is about 0.04mm out of parallel.
          > >
          > >
          > > What tolerance should i be aiming for, or can expect to achieve assuming I can improve the table accuracy?
          > >
          >
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