When I was young I got a job at a manufacturing place that made all sorts of parts for sensitive equipment. Younger people, or people with steady hands would debur and smooth. We would have these huge magnifiers and friggin microscopes and be working with what looked like a really long tiny exacto knives that needed to be replaced every 5 minutes or a couple dozen uses to get that stuff to spec. You can spend 20 minutes on a piece, think it's perfect and then QC would send it right back because they somehow found some tiny inconsistency or groove you didn't or couldn't notice.

There is no way you can expect that level of accuracy, unless your willing to pay for clean room level stuff. Even we weren't always quite that accurate depending on the end use and they charged like almost $50 for something that looked quite like something you get a hardware store for 50 cents.