As Prof Chris said, we are discussing very small "inaccuracies". Nowadays much closer tolerances can be achieved than a man could in the (say) eighteenth century, working with hand tools only, but that is not to say that the eighteenth century standards were not good enough. We have to strive for the highest level of accuracy and consistency, that's the way we are wired, but good enough will do.
I cut my fret slots by hand, to the rule of 18, using a very rudimentary jig. It works for me.
I cut my fret slots by hand, to the rule of 18, using a very rudimentary jig. It works for me.