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RE: [mill_drill] Edge Finders - pros and cons

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  • Cecil Strange
    If you do not know that the edge of your workpiece is flat and square to less than .001 , and if you are relying on the accuracy of a leadscrew in a mill drill
    Message 1 of 25 , Sep 24, 2010
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      If you do not know that the edge of your workpiece is flat and square to less than .001", and if you are relying on the accuracy of a leadscrew in a mill drill for positioning, then finding an edge to greater than .001" accuracy is never going to matter.  All you need to do is run the revolving cutter into a piece of cigarette paper stuck to your edge.  That will get you almost as close as a mechanical edge finder, doesn't require going back and forth to be sure of yourself, and is fast because it eliminates a tool change.

      For a center punch mark, judging a wiggler by eye should be good enough, and you should use a centering scope if it isn't.

      For a hole, I use an indicator to learn about the edges relative to the X and Y axes and whether the hole is round.  The size of the hole and the tolerances I have to work to sometimes dictate a more expedient choice.
    • picclock
      Thanks for the Edge Finder comments, it seems to have elicited a large number of responses. I ve ordered an 827MB which should be here today or Monday. The
      Message 2 of 25 , Oct 2, 2010
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        Thanks for the Edge Finder comments, it seems to have elicited a large number of responses.

        I've ordered an 827MB which should be here today or Monday.

        The trick with the cutter and paper relies on the cutter diameter being known to be correct - something I would not like to rely on. Having said that for some noncritical jobs I have been guilty of using a similar technique.

        My mill is digitised on all three axis so I am under the illusion that I think I know where I am :-) . To be fair I have measured the relative accuracy of work done using digital positioning, and am always amazed at how accurate it seems to be. It's also a lot easier to work with.

        Many Thanks

        picclock

        (still very much a beginner)

        --- In mill_drill@yahoogroups.com, Cecil Strange <cecil_strange@...> wrote:
        >
        >
        > If you do not know that the edge of your workpiece is flat and square to less than .001", and if you are relying on the accuracy of a leadscrew in a mill drill for positioning, then finding an edge to greater than .001" accuracy is never going to matter.  All you need to do is run the revolving cutter into a piece of cigarette paper stuck to your edge.  That will get you almost as close as a mechanical edge finder, doesn't require going back and forth to be sure of yourself, and is fast because it eliminates a tool change.
        >
        > For a center punch mark, judging a wiggler by eye should be good enough, and you should use a centering scope if it isn't.
        >
        > For a hole, I use an indicator to learn about the edges relative to the X and Y axes and whether the hole is round.  The size of the hole and the tolerances I have to work to sometimes dictate a more expedient choice.
        >
      • rick_kruger
        A bunch of very good replies, great information. I mostly use the standard mechanical (spring) edge finders, for both edges and finding the center of holes.
        Message 3 of 25 , Oct 9, 2010
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          A bunch of very good replies, great information.

          I mostly use the standard mechanical (spring) edge finders, for both edges and finding the center of holes. Learned the cigarette paper trick in my dad's shop in the 60's and still use it occasionally. Use the conical mechanical edge finder for centering holes. I have and use the laser pointer edge finder when the location isn't critical, but find it far more satisfying to "know" where the edge is via the mechanical finder.

          One caveat on finding hole centers that really hasn't been mentioned. To effectively use the conical edge finder to center holes, you really have to know what your backlash is (to close to 0.001") on both X and Y axes. If you don't, you really don't know where you are. What makes it so easy for me, is the use of DROs. Eliminates the backlash issue altogether.

          Same thing applies to finding a straight edge, depending on how you are going to approach it with a cutter.

          Rick

          --- In mill_drill@yahoogroups.com, "picclock" <mdare@...> wrote:
          >
          > Hi
          >
          > I've decided I need to get a 'real' edge finder as I have a job coming up which will need positioning to better than 1 thou.
          >
          > I've looked up info on the internet and found the following.
          >
          > Laser edge finders are not accurate - especially on an edge.
          >
          > Electronic ones are a little better but often don't have a well defined on/off point leading to inaccurate settings.
          >
          > Optical ones seem quite good - One I found with a webcam looked very easy to use but I would need an old laptop or similar for a display which seems a bit of overkill. Another older design loked like it was part microscope which fitted to the mill.
          >
          > Wobblers seem to get very good press for repeatabilty and accuracy. The only small problem I forsee is that centering on a punch mark, small hole or shallow inside edge would be difficult/impossible.
          >
          > At the momement I'm just chucking up a piece of rod and subtracting half the diameter. But I don't normally do anything that requires a high degree of accuracy.
          >
          > Any buying/using advice welcome
          >
          > picclock
          >
        • Johnny
          Definitely use the spring type Rick mentioned, and, do yourself a huge favor - buy a Starrett, I promise you won t regret it. I would avoid using punch marks.
          Message 4 of 25 , Oct 10, 2010
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            Definitely use the spring type Rick mentioned, and, do yourself a huge favor - buy a Starrett, I promise you won't regret it. I would avoid using punch marks. Holes are easily located by just an X and a Y dimension. Locate using your Starrett. Layout lines, with the help of the conical or pointed end of the Starrett, will warn you if you've screwed up. Lock the table, start the hole with a center drill, then drill that bad boy. I do accurate drilling all the time, and that works for me. Might work for you also. If you are using a mill-drill, you might have a problem with quill slop, rendering it unable to hold its position. I used to have a Rong Fu and with it drilling holes with precision was challenging. Repeatability was also an issue. I sold my RF five or six years ago, so I don't know if quill slop is still a problem or if work-arounds have been devised. Good luck with your project.

            John

            --- In mill_drill@yahoogroups.com, "rick_kruger" <krugerr@...> wrote:
            >
            > A bunch of very good replies, great information.
            >
            > I mostly use the standard mechanical (spring) edge finders, for both edges and finding the center of holes. Learned the cigarette paper trick in my dad's shop in the 60's and still use it occasionally. Use the conical mechanical edge finder for centering holes. I have and use the laser pointer edge finder when the location isn't critical, but find it far more satisfying to "know" where the edge is via the mechanical finder.
            >
            > One caveat on finding hole centers that really hasn't been mentioned. To effectively use the conical edge finder to center holes, you really have to know what your backlash is (to close to 0.001") on both X and Y axes. If you don't, you really don't know where you are. What makes it so easy for me, is the use of DROs. Eliminates the backlash issue altogether.
            >
            > Same thing applies to finding a straight edge, depending on how you are going to approach it with a cutter.
            >
            > Rick
            >
            > --- In mill_drill@yahoogroups.com, "picclock" <mdare@> wrote:
            > >
            > > Hi
            > >
            > > I've decided I need to get a 'real' edge finder as I have a job coming up which will need positioning to better than 1 thou.
            > >
            > > I've looked up info on the internet and found the following.
            > >
            > > Laser edge finders are not accurate - especially on an edge.
            > >
            > > Electronic ones are a little better but often don't have a well defined on/off point leading to inaccurate settings.
            > >
            > > Optical ones seem quite good - One I found with a webcam looked very easy to use but I would need an old laptop or similar for a display which seems a bit of overkill. Another older design loked like it was part microscope which fitted to the mill.
            > >
            > > Wobblers seem to get very good press for repeatabilty and accuracy. The only small problem I forsee is that centering on a punch mark, small hole or shallow inside edge would be difficult/impossible.
            > >
            > > At the momement I'm just chucking up a piece of rod and subtracting half the diameter. But I don't normally do anything that requires a high degree of accuracy.
            > >
            > > Any buying/using advice welcome
            > >
            > > picclock
            > >
            >
          • rick_kruger
            I have to agree. This is definitely a place I found it pays to buy the best, or at at least Starret. Had import edge finders. Barrel dimensions were not to
            Message 5 of 25 , Oct 11, 2010
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              I have to agree. This is definitely a place I found it pays to buy the best, or at at least Starret. Had import edge finders. Barrel dimensions were not to specs. Had trouble getting them into the collets (R8). Bought a Starret set. No problems. Love 'em. Don't particularly notice a difference in the edge finder functions, just a whole lot easier to insert into the collets, which saves time and frustration.

              Rick

              --- In mill_drill@yahoogroups.com, "Johnny" <jttoner@...> wrote:
              >
              >
              > Definitely use the spring type Rick mentioned, and, do yourself a huge favor - buy a Starrett, I promise you won't regret it. I would avoid using punch marks. Holes are easily located by just an X and a Y dimension. Locate using your Starrett. Layout lines, with the help of the conical or pointed end of the Starrett, will warn you if you've screwed up. Lock the table, start the hole with a center drill, then drill that bad boy. I do accurate drilling all the time, and that works for me. Might work for you also. If you are using a mill-drill, you might have a problem with quill slop, rendering it unable to hold its position. I used to have a Rong Fu and with it drilling holes with precision was challenging. Repeatability was also an issue. I sold my RF five or six years ago, so I don't know if quill slop is still a problem or if work-arounds have been devised. Good luck with your project.
              >
              > John
              >
              > --- In mill_drill@yahoogroups.com, "rick_kruger" <krugerr@> wrote:
              > >
              > > A bunch of very good replies, great information.
              > >
              > > I mostly use the standard mechanical (spring) edge finders, for both edges and finding the center of holes. Learned the cigarette paper trick in my dad's shop in the 60's and still use it occasionally. Use the conical mechanical edge finder for centering holes. I have and use the laser pointer edge finder when the location isn't critical, but find it far more satisfying to "know" where the edge is via the mechanical finder.
              > >
              > > One caveat on finding hole centers that really hasn't been mentioned. To effectively use the conical edge finder to center holes, you really have to know what your backlash is (to close to 0.001") on both X and Y axes. If you don't, you really don't know where you are. What makes it so easy for me, is the use of DROs. Eliminates the backlash issue altogether.
              > >
              > > Same thing applies to finding a straight edge, depending on how you are going to approach it with a cutter.
              > >
              > > Rick
              > >
              > > --- In mill_drill@yahoogroups.com, "picclock" <mdare@> wrote:
              > > >
              > > > Hi
              > > >
              > > > I've decided I need to get a 'real' edge finder as I have a job coming up which will need positioning to better than 1 thou.
              > > >
              > > > I've looked up info on the internet and found the following.
              > > >
              > > > Laser edge finders are not accurate - especially on an edge.
              > > >
              > > > Electronic ones are a little better but often don't have a well defined on/off point leading to inaccurate settings.
              > > >
              > > > Optical ones seem quite good - One I found with a webcam looked very easy to use but I would need an old laptop or similar for a display which seems a bit of overkill. Another older design loked like it was part microscope which fitted to the mill.
              > > >
              > > > Wobblers seem to get very good press for repeatabilty and accuracy. The only small problem I forsee is that centering on a punch mark, small hole or shallow inside edge would be difficult/impossible.
              > > >
              > > > At the momement I'm just chucking up a piece of rod and subtracting half the diameter. But I don't normally do anything that requires a high degree of accuracy.
              > > >
              > > > Any buying/using advice welcome
              > > >
              > > > picclock
              > > >
              > >
              >
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