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ringed drive dog

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  • ringed drive dog

    In James Harvey's Machine Shop Trade Secrets, he is shown using what appears to be a drive dog made from a simple sleeve attached to the headstock center with socket head screws to 'drive' into the face of the work. Has anyone else used this before?

  • #2
    It is called a pot chuck, and it is the oldest form of lathe chuck.
    Today we carve our own omens Leonidas at Thermopylae

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    • #3
      Ok, then. Are you sure though... doesn't a pot chuck's screws run perpendicular to the work? These run axial.

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      • #4
        I dont have that book and you guys come up with some of the neatest stuff here. Do you have a picture of this thing? please post it!

        A pot-chuck to me is a collet with a large machinable flange split in three pieces. Tightening the the single screw in the center spreads the collet outwart to hold onto the ID of a part.

        Ron

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        • #5
          Something like a Giromat?



          These work by he driving dog with teeth in, climbing up the three balls and ramps as so forcing the teeth into the work to drive.

          John S.
          .

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



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          • #6
            What? Show us John.

            ------------------
            Gene
            Gene

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            • #7
              Closer.

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              • #8
                On the flat front face of the body [ top of the pamphlet ] there are 4 indents that take a bearing.
                The drive dogs [ plenty in the box ] with ratchet type teeth on drop onto these balls by the 4 grooves in the back.
                A spring loaded centre runs up the middle and a slide on sleeve [ on the right ] keeps everything together.

                In use you fit this into the headstock taper and mount your shaft between centres and tighten the tailstock so the headstock end of the bar digs into the ratchet drive dogs.
                You are now ready to start turning.
                If and when cuting forces try to turn the shaft against the ratchet teeth the ratchet part rotates and because it's sitting on 4 balls in a ramp the balls climb up the ramps and cause the ratchet part to extend and dig further into the work.

                The leaflet that came with it has been soaked in oil over the years and it's made the pages transparent.
                If you look closely you can see a diagram of how it works on the back of the middle page.
                The top drawing shows the grooves out of line causing the balls to ride up and put pressure on.

                These were designed for auto lathes so they could do all the turning work between centres in one go without having a driving dog.

                This one was made by Myfords for their Minikop copy lathe.
                You can often see the marks left by these type of tools on commercialy produced shafts.
                Look for some radial chisel type marks on the ends of shafts etc.

                John s.
                .

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



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                • #9
                  Ok I am dense
                  I have read the description three times and looked at the pictures and I still dont know what it does or how it works. Anyone have a web site?

                  Ron

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