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Torsion clock pendulum project

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EricB:
The top and bottom pieces that make up the gallery are probably the most complicated parts to make. The shapes are 35mm diameter circles that are cut in by three 20mm radii 120 degrees apart. The center distance between the part and the 20mm radius determines the final shape and size.

To make these I needed to sweep the radius and index the parts. I piled up a rotary table with an accessory plate and an indexing head. The parts where held on a mandrel made from the stub the finial was cut from.

I started with thicker stock just large enough of the parts and turned them into semi circles. After I trashed the first one I found this step was not needed.

I made three of these. The first was too small because I did not get the center distance right. I also did not have enough travel in my setup and could not complete the cuts. I used the scrap as my test piece for later operations.

I did get the curves and sizes right in the end.

EricB:
The next steps for the gallery parts were reducing them to their final dimensions, drilling holes for the three steel pillars, and making the pillars.

The drill rod I used for the pillars was a few thou larger than the holes left by the drill so I sized the pillars with some sand paper.

The final work on the gallery was to drill and tap for the custom screws that hold it all together, and make all the screws.

EricB:
The final machining on this project was to make the hook that attaches the pendulum to the clock. The sample I'm copying has the hook riveted in place. The original parts had the hooks threaded so I went that route. That way too I could fix all the finishes later.

I did not take any pictures of the process, but I started with the threaded end using my scrap part to get them to the correct length. From there I turned the OD and parted off a bit long. I threaded a mandrel to match the hook blank and finished the top shape.

From there I made the hook itself. I've made number of these so I have a special fixture. First the part is cross drilled for a pin, then the central slot is cut from the top down. The part is rotated 90 degrees in the fixture, and the fixture repositioned, then the side cut is made to complete the hook.

None of this build was very difficult, but there are not many people who do this kind of work.

EricB:
Here is the final part in action. I said earlier the using the old nut was a bad idea. You can see the large disk wobbles because the threads in the nut are not square with its mating surface. I'll sort that out when I polish it up.

Thanks for looking.

Eric

http://www.youtube.com/watch?v=dUw8E3m2sXc

Chipswitheverything:
Thanks for the write-up and the excellent photo sequence outlining this quite tricky horology job, interesting.  Dave

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