Remember those round slide rules… Do you know how easy they are to use really?
Well, say you had a big round table with a big worm about 120 or 180:1 . Now your scale is big, remember divisions break down quickly into recurring fractions. A big vernier is nice, on my big Rabone Chesterman ( the inside jaws are so half inch) the vernier is fully 2.45 inches. But 9 goes nicely into 360, so how would you number a complete circle decimal vernier scale… to read negative rotations?
Regards,
Ant