Eli5 How was the first industrial machine made without the precision of machinery?

Question

How do you make a machine that has perfectly flat/plumb/level metal components without the aide of a machine to begin with?

In: 224

Answer 1

Not that long ago 50-60years they used build lathes and mills by [scraping ](https://en.m.wikipedia.org/wiki/Hand_scraper) in the ways. On industrial scale not done anymore but plenty of hobbyist do it to this day.