Made progress on the roundel last night. I’d like to say that I anticipated all contingencies and things went to plan, but much cursing and on-the-fly re-engineering ensued.
I had a piece of ~5/8″ walnut already milled. The interior diameter of the base hole was 5-13/16″; I split the difference and set the cutter. Started the cut, and realized the cutter was set for an exterior diameter (the cutter is tapered on one side and flat on the other – set the flat to the outside and it cuts a hole with the exterior edge of the cutter; set the flat on the inside, and it cuts a flat sided disk). Swapped the cutter, and started over on a new piece of the same board. Cut for a while, with much burning. Flipped the board and continued cutting. Progress was slow, my nose was filling with acrid walnut smoke, so I took it to the bandsaw and trimmed the excess outside the groove being cut. This necessitated screwing the blank to a backer board to keep my fingers away from the arm on the fly cutter as it spun around at 500 rpm. But the cutter no longer burned, and quickly sliced through the remaining material, leaving me with a perfect disk.
Set the router up for a 3/16″ x 1/4″ rabbet and cut the rebate.
The rest of the night was a matter of adjusting fit and planing the roundel thinner. I decided to router a little more after the roundel was too thin to leave on the bench (the screw holding the bearing in place on the bit would contact the benchtop), so I mounted the piece on a block of wood with double sided carpet tape. The final fit is a little loose in the camera base, but won’t affect the gluing – it’s the top portion of the plate where the glue surface lies.
I realized somewhere in this process that I can remount the roundel and set the fly cutter to exactly the diameter of the existing rabbet in the camera bottom and fit the piece in perfectly, without altering the camera physically.
So, that’s where I left off. A new wrinkle became apparent, though – the threaded insert is longer than the roundel is thick. I checked the penetration of the tripod screw by setting the roundel on the tripod, and the screw just peeks above the roundel. So, I’ll need to modify the threaded insert, or the camera bed will contact it and be limited in travel.