Using a cheap rotary index and some 1/4" x 5 1/2" acrylic discs. Drilled the holes using the DRO bolt circle function. Made 5 discs using numbers not possible with the original rotary index, up to 48. May make more if needed--they are pretty easy to make
It is a function of some?(most)? DRO's that will give the coordinates of the xy axis to drill holes for a given diameter.
You enter your center of a cirlce x-0/y-0 and the diameter of the circle you want, the number of holes, the start and end angles.
Edit: Also known as Pitch circle diameter--probably the correct name.