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Re: Finding Center of Round Stock

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  • Rick Kruger
    Why would it matter how you got to the other side, either by raising the quill, removing the edgefinder or running the table left/right to clear the end of the
    Message 1 of 45 , Feb 4, 2004
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      Why would it matter how you got to the other side, either by raising
      the quill, removing the edgefinder or running the table left/right to
      clear the end of the part/vise and moving the table back into
      position? Once one edge is found, the table dial can be reset to
      zero (or DRO if you have one), then what I do is move the table 1/2
      the dia. of the edge finder probe, and reset the dial/DRO to zero so
      the centerline of the spindle is centered over the edge of the part
      just "found". Then, it is an easy matter to move into the part
      whatever the distance is that you need to drill/mill. In this case
      its half the dia. of the part. Measure the part to determine its
      diameter and do the math. It is also sometimes possible to "edge
      find" on the corresponding vise jaw face, the jaw holding the
      opposite side of the part. I don't think this is as accurate as
      measuring the part directly, but its probably close enough for lots
      of situations. If you are lucky enought to have a DRO that does the
      centerline computation for you, its a snap to edge find both sides
      and use the DRO to do the math.

      I use a DRO so backlash is not an issue as far as locating centers or
      other points. It is an issue when milling, and I tend to account for
      it in positioning the table even for drilling, but this occurs after
      the "position" is located using the edge finder & DRO.

      Another way to end drill the center of a round part held vertically
      in the mill is use a stop on the side of the jaw, such that a 90 deg
      corner is formed (one that reaches the centerline of the stock),
      edgefind both surfaces of the jaw and stop, set both to zero,
      establishing a 0,0 datum at the corner of the jaw/stop, then dialing
      over 1/2 the stock dia. from both axes. I use this ALL the time, for
      nearly all my milling/drilling. When I'm done with one
      operation/part, I return the spindle to the 0,0 datum location and
      lock down both table directions and turn the DRO off. Then, when I
      return for another operation (hours, days, weeks later), I have the
      same 0,0 datum to start from. (Often I verify this if its been more
      than a short time between). The DRO maintains is coords. even when
      off, but even if it doesn't, just resetting zero on both axes before
      moving the table re-establishes 0,0.

      Another way to do the end center drilling would be to set up a rotary
      table with a 3-jaw chuck, center it by whatever method you like (I'd
      use a piece of tubing and a test indicator, but have used a dead
      center in the spindle held firmly into the centerhole of the RT
      for "less accurate" needs). Then put the round part in the chuck and
      drill away. This takes some setup time but works very well,
      especially for multiple parts.

      Rick


      --- In GrizHFMinimill@yahoogroups.com, "Jim E." <jim0000@a...> wrote:
      > BIll:
      > Many of the recommendations you're receiving will only give
      > approximations if the sides or end edges of the workpiece aren't
      smooth. Running any device, no matter the type, across rough or non-
      trued surfaces will give only approximations. Question is, to what
      level of approximation can you live with?
      >
      > Plus, to those who are advocating the use of an edge finder to
      locate the center, whether while flat or on end: how do you do so
      without
      > a: lifting the spindle to get the finder over to the opposite
      side, or
      > b: removing the finder from the collet, then re-inserting it after
      > moving the piece to the other side of the spindle?
      >
      > Graciously,
      > Jim
      > Lakewood, CA
      > All Hail Rube Goldberg!
      >
      > dswr@w... wrote:
      >
      > > Bill, you are right... about the assumption of a diameter of
      1/2". I was thinking of the original post where the question was
      about drilling a 1/4" hole through the side (diameter) of a 1/2"
      round bar. Sorry 'bout
      > > that!
      > >
      > > Also, the diameter of the Edge finder can be some dimension other
      than 0.200".
      > >
      > > Leo (pearland, tx)
    • Barry Young
      Hi guys: I would recommend that you pick up an edge with an edge finder, move in .500 and drill a hole. Then measure the distance from the edge of the part to
      Message 45 of 45 , Feb 6, 2004
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        Hi guys:

        I would recommend that you pick up an edge with an
        edge finder, move in .500 and drill a hole. Then
        measure the distance from the edge of the part to the
        center of the hole. This is how you find as I have
        done, exactly how far you are from the edge you are
        when you use an edge finder. I am .0001 from the edge
        with my edge finder and with the techniques I use. So
        do the experiment and test your own techniques. Every
        tool and every machinist will get different results.
        The only way to be sure is to try it.

        Barry Young


        --- h12721 <73772.2557@...> wrote:
        > --- In GrizHFMinimill@yahoogroups.com,
        > ljack70117@a... wrote:
        > > When the edge finder jumps off as you said, it is
        > .0005" past the
        > edge.
        > > Thank you
        > > Larry Jackman
        >
        > Hi Larry, where does the 0.0005 come from? Could
        > it be 0.0004 or
        > 0.0006 or 0.0001 or what ever? At what speed?
        > Regards Hilmar
        >
        >
        >
        >
        >
        > >
        >
        >
        >
        >
        >
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