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Machining hemispheres on a milling machine

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  • Machining hemispheres on a milling machine

    There have been several threads here asking how to mill concave or convex hemispheres. I just noticed this YouTube video on PM which shows the textbook (Moltrecht, Cincinnati, Brown & Sharpe, ...) setup -- it's fun to watch. Quite the Rube Goldberg contraption to drive the rotab

    http://www.youtube.com/watch?v=3psLvh5ssPQ&
    "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

  • #2
    Another way

    http://www.ipstool.com/Catalog/0185.pdf

    But you need to use the lathe. The ting I wonder about is just how does he control the size of his radii?
    Forty plus years and I still have ten toes, ten fingers and both eyes. I must be doing something right.

    Comment


    • #3
      And here's the final product: a beautiful bronze bearing for a 1916 locomotive:

      http://www.youtube.com/watch?v=fuZQsLR7ty8
      http://www.youtube.com/watch?v=8Pfc6q8t45c
      "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

      Comment


      • #4
        Originally posted by Spin Doctor
        Yeah, I have a Holdridge clone, but it's not nearly as cool as doing it in the mill
        "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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        • #5
          Pretty 'simple' way of doing it, I can see some experimenting going on in the shop pretty soon.

          I'd read the method being described before, but apparently whoever described it had the process mixed up

          Wonder if there are practical limits to the smaller sizes you can do this way.

          Ken.

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          • #6
            Can someone please explain how a bearing can have another shaft at 90 degrees I just cannot see how anything can rotate!
            Peter
            I have tools I don't know how to use!!

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            • #7
              As I see it, it rotates with the shaft and rides in something else (the two flat on the outside) the sherical section is to allow the shaft to rock a bit.

              Looks to be something of a U-joint actually.

              ken

              edit: would like to see the making of the shaft.
              Last edited by kendall; 01-20-2008, 06:14 PM.

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              • #8
                How much do these holdridge ones cost and are they still manufactured??Alistair
                Please excuse my typing as I have a form of parkinsons disease

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                • #9
                  They are high And yes still made by Holdridge
                  Every Mans Work Is A Portrait of Him Self
                  http://sites.google.com/site/machinistsite/TWO-BUDDIES
                  http://s178.photobucket.com/user/lan...?sort=3&page=1

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                  • #10
                    Alistair

                    Holdridge are quite expensive but are easy enough to homebrew.

                    Jon Bohlander
                    My PM Blog

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                    • #11
                      That aint Rube Goldburg. Thats getting it done. Been their done that
                      Every Mans Work Is A Portrait of Him Self
                      http://sites.google.com/site/machinistsite/TWO-BUDDIES
                      http://s178.photobucket.com/user/lan...?sort=3&page=1

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                      • #12
                        As far as setting the radius, you measure from the front of the inner frame (Holdridge has flats on their cast frames) to the front of the tools and subtract the distance from the front to the center of the pin it rotates on. It's nice to have gages cut out of plate for the common radii.
                        Jon Bohlander
                        My PM Blog

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                        • #13
                          Yes, the Holdridge Radius attachments are still made.

                          This site is on the internet has them for sale.

                          http://getmachiningtools.com/pro1115077.html

                          Here is another, or rather two other rare radius attachments.



                          The center, and left side components are a reduction geared feed head,

                          and adjustable internal, and external cutting bars.

                          The mechanism is outside the part, so the pivot point, or shaft

                          of the attachment does not get in the way of the machining operation.

                          The unit on the right is like a rotary table mounted in the slotted

                          bar.

                          Both will cut to center of the sphere. Most other attachments will not.



                          This is the offset setup machining a spherical socket (cannonball mold) in the lathe.

                          Kap

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                          • #14
                            Originally posted by Alistair Hosie
                            How much do these holdridge ones cost and are they still manufactured??Alistair
                            Here you are Ugly.

                            On this page.

                            http://www.arceurotrade.co.uk/en-gb/dept_175.html




                            .
                            .

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



                            Comment


                            • #15
                              Oh, come on John -- Alistair can make one in a couple of hours.
                              "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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