@isocat @catsalad @GustavinoBevilacqua Almost! I was thinking that several of the photographed ones were very hard to cut but there's even more challenge in a couple of the diagrammed ones. The 20th century lathes that I learnt on weren't made for things like the "holes not square" thread nor the "all size tapers". But a 19th century or earlier lathe is more open to those sorts of turning, and so were the lathes of the 16th century when people did things like elliptical cross-sections for fun.