I recall reading (I apologize that I can't remember where) that the milling machine rested upon two
distinct achievements: flat and straight ways, and the precision lead screw. Terry gave us a
description of how the former could be achieved through ink and painstaking iteration, and how
relatively imprecise lathes can be used to produce very round products. The lead screw couples
translation with rotation. I don't recall how the first precision lead screw was fabricated, but I do
remember a comparison to viral replication: once such a screw was in hand, it could readily be used
to fabricate numerous copies (at different scales), which could then be used to generate additional
copies. It's not clear how precision was increased over time (paintaking iteration? or perhaps some
sort of mechanical averaging?) but no doubt there's an interesting story there.
Regards,
-Ben Shaw
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