Watching this amazing hand/eye skill reminds me of a story I heard when I worked for AVRO/Hawker Siddelley/BAE in Chadderton, Manchester, in the 70s:
So, it was England's darkest hour, WWII was not going well and the USA had offered to help out.
So it was Pratt & Wittney and Rolls Royce as the 2 main precision companies.
After a bit of banter (see below*) P&W sent the "Worlds Smallest Bolt" to RR.
What did RR do? Took the "Worlds Smallest Bolt", drilled and tapped a hole in it and sent it back to P&W
* Bit of banter:
P&W offered to build the RR Merlin engine for Spits/Lans/Mustangs.
RR sent them the drawings and specs.
"No way can we build to these tolerances says P&W"
So what did RR do?
Crated up an engine from a Spit with about 1000 hours on the clock, shipped to P&W, quote was "Check this out, its STILL in tolerancer after being in combat"
P&W then found they could build Merlins
Now I refuse to get into the Comet vis a vee the 707 debate