Our Education Department was hosting a family workshop for making clocks out of slices of logs, and wanted a way to treat the face of the clock so that it was more attractive than the rough-sawed wood.
I devised a system where we could dish-out the face of the log 0.75" and leave the bark and last few growth rings intact. In preliminary test this outer ring would blow apart during fly-cutting the entire surface.
I created a holding jig with a 90 of hardwood and a couple of De-sta-co clamps.
At the 90 and 180 degree quadrants I installed some screw tips peeking out.
The log was tapped against the exposed screws and clamped.
I created a tool path based upon the smallest log diameter, and printed off a centering template to be placed on the fixtured log.
Here is the finished product. The hole for the clock mechanism was made using a forstner bit on a drill press rather than using the 'Bot. If I was making a a few hundred of these rather than 15, I might have expended the extra effort to make jig for the CNC machine. It did not make sense to expend that effort in this instance.