I suppose a CAD program is the wrong tool for the job then. For example, I often found Illustrator to be the wrong program for what I was using it. I only used it because I had it, and because I really needed vector graphics. I am sure that there are people who design gage dials, scales, and watch dials, but I have no idea what software they use. A movie prop maker I know recommended Deneba Canvas, but I am totally unfamiliar with it.
I can and probably will design the scales in Photoshop, because I know how to do it with it, but it will be tedious. Gah! I plan on printing out a negative on Press-n-Peel Blue transfer film. The film goes on a paper-thin brass sheet, which is then etched. The etched dial goes on a painted metal disk, that way I have a brass colored dial with colored numbers.
The slide rule will consist of two discs (each made from a thick base with the thin, etched dial on top of it), one smaller inner with the angle units and the target size, and one larger outer dial with the target distance. I'm shooting for a dial with 70 mm radius, which will give good enough resolution.