I made a temporary base for the clock from scrap 3/4" plywood which will permit running the clock before the wooden base is constructed. It will also permit testing the positioning of the columns relative to the dome -- if the dome isn't positioned correctly the clock won't fit under it.

To do this, I extracted a Deltacad template from the main drawing, which shows the position of the columns and the circle which represents the dome base. I used the template to mark the base column-mounting holes on the wood, and I Also used it and a compass to make a pencil line on the wooden base which indicates the position of the dome.

To drill the holes, I used a 1/4" Forstner bit, which drills clean holes. The position of the holes is tested using the actual brass upper balance bridge plate. When the time comes, the Deltacad template will be used to drill holes in the actual wooden base.

I used 1/4" fine-threaded brass studs to bolt together the columns, upper balance bridge and movement base plate. I also used the same together with 1/4" nuts to bolt the columns to the 3/4" plywood base.

I also mounted the movement to the movement base plate. Four holes must be drilled in the base plate for screws through the transverse mounting holes in the bottom pillars of the movement. First, I used the register marks on the paper on the base plate and the corresponding register marks on the paper on the movement plates to get plates and base in alignment. Then I used a transfer punch to transfer the position of the mounting holes in the pillars at the bottom of the movement. These transfer punches are available in sets, and one can be found which is a close fit to the holes in the movement bottom pillars, thus ensuring an accurate transfer of the position of the holes.

The mark made by the transfer punch acts as a center punch, making starting divots in the base plate. As usual, I marked, drilled, and tapped one hole at a time. I put in one screw, used it to screw the movement to the plate, and then marked the next hole, drilled and tapped it, and so on. This reduces the chance of error.

I also made two small columns, the ones which suspend the lower balance bridge to the upper balance bridge. These are made from 1/4" hex brass rod. They are 1-1/2" long, made to separate the balance bridges 1-1/4". The end spigots are drilled and tapped for 4-40 screws. I did the tapping in the Taig lathe to be sure that the tap enters the holes accurately. Taps that enter a bit crooked into a long hole can snap unexpectedly. The tapping was done by turning the lathe spindle by hand.

The columns were finished as before with fine sandpaper, then Scotchbrite pads, then steel wool, then with tripoli on a leather buff. The flats on the columns were fine-line finished with buffs. It's convenient to screw the columns onto a piece of dowel or pegwood for cleaning and finishing, so that fingerprints are kept at bay.

With the balance bridges and plates all together, I put the balance itself in the unfinished bearing holes in the bridges, just to get a first glimpse of how the clock will look.

Todays' links:

Wooden base
Register marks
Transfer punch
Tapping columns
Column with pegwood
Polishing hex flats
Balance and bridges
Current state
Base template, Deltacad download
Base template, dxf file download