If you want to make a range of gears between 15 and 136(rack) you would need 136-15 = 121 cutters, that have a true convolute shape. Because this is a little bit over the edge, they divided this over 8 ranges. Take a look at a gear hobber and try to figure out, how these machines make with 1 mill per modula, perfect gears. Try to figure out the difference between the mill in the link (incorrect) and Geof's hobber mill (correct). Hint: Every tooth is corrected off-center. After that you will see the unavoidable imperfection of the gear cutter.
Carel |