In the first Machine Thinking video he presents the Watt micrometer as one of the worlds first precision measuring tools. I would like to ask how early clock makers and engineers measured precise tolerances without a preexisting reference tool? And how could they be confident that any tools they made themselves could maintain accuracy over a variety of measurements?
A lot of credit should go to Henry Maudsley, an English mechanic who did a lot to create the first precise machine lathe, with a lead screw and compound rest for the cutting tools. That made it possible to make precise screw threads , and being able to make precise screw threads made micrometers possible. His famous "Lord Chancellor" micrometer, capable of measuring .0001", is at the Science Museum in London, along with some other of his inventions.
Clock and watch makers could work to pretty close tolerances because it is possible to fit small things, like gears and pinions, quite closely with simple lathes and scrapers, files. An 18th c. wheel cutting engine, for doing gears, could be entirely hand powered and do quite close work. But those gears and pinions were, again, being fitted. They were not being repeatedly generated to spec. The "American System" really did depend on machine tools.
Yes, eventually Jo-blocks were made that were quite precise- ( thank Henry Ford for that, Ford put Johanssen into business) but that was after decades of increasing precision, standardized measurements , thread specifications by engineering societies. Johanssen had master gauges and very good micrometers, was also able to use surface grinders capable of such accuracy.
David S Landes Revolution in Time
Joseph Wickham Roe: English and American Tool Builders
"Precision measurement" originates with astronomy, as you need to get angles measured very precisely to get to constellation movements. This is actually not that hard to achieve if the measuring instruments are big enough, and the mathematical foundation for these actions have been around for millenia - this is what "construction with compass and a ruler" in geometry is all about.
Essentially, to divide a unit of any length in 100 parts, you need to build a parallel line far apart; create 100 equal parts of any length on that line (by design - repeat any length 100 times over); draw lines from the end points of the pre-divided length through the end of the length to be divided; and put lines from that intersection point to ends of each of 1/100's. The intersections of those lines with the length to be divided would give you 1/100'th.
This is described in Proportion 10 of Book 6 of Euclid's Elements.