Normally I would assume that a YouTuber claiming to have built a more accurate DIY CNC lathe than Dan Gelbart's was full of shit, especially if he didn't mention Gelbart in the title. But Cylo's Garage is an exception. His objective is diamond-turning optics. So he does need tighter precision than Gelbart's 1μm, and he's been working toward achieving it in an astounding fashion for years—inspired, he tells us in the video, by Gelbart.
This video, though? You know how people say "this meeting could have been an email"? This video could have been a web page. Or an email. It's just a set of slides with a voiceover. Save yourself the time and just read the subtitles:
yt-dlp --write-info-json --write-sub --write-auto-sub --sub-lang en --restrict-filenames https://www.youtube.com/watch?v=vEr2CJruwEM