[Dick Linn]

Lead screws can be made exceptionally accurate. Moore Tool developed jig boring machines that are very accurate and they used lead screws. Richard Moore has been recognized as the man who "gave the world’s industry an additional decimal place of accuracy!"

His son Wayne wrote the book "Foundations of Mechanical Accuracy".

I don't know what they use these days, but they have jig grinders that will position within 90 millionths of an inch in 18 inches of travel.