[kragen]

Yes, quite commonly he spends several days making a part where he gives you all the dimensions and tolerances in three minutes at the beginning of the video, and the reason it takes several days is that if at any point he screws up, the part will obliterate him, his lathe, both, or his client, so he doesn't rush anything. And, yes, he spends a lot of his time coping with non-idealities. These are among the reasons that whipping up a quick Perl script is so much faster than whipping up a quick hydraulic cylinder.