Hi Richard,
Those setting circles look really cool
May I suggest one little thing: to improve the visibility (by reducing the number of lines) and still keep the same resolution, perhaps you could design the suitable vernier for each scale? This may be a bit fiddly to do (scale of the printout for each vernier must be reduced by appropriate factor, 9/10 or 5/6), but this may be be useful..
Such verniers were/are used on old-fashioned sextants and callipers (sometimes they have also magnifier for more accurate reading, not necessary here of course).
http://en.wikipedia.org/wiki/Vernier_scale