For my final project in a course called fundamentals of machine shop operation, I fabricated a metal turbine using manual lathe and conversational milling work. The tolerances were, in certain points, extremely tight, with bores with tolerances as small as around 0.002", and a couple stainless steel diameters with tolerances as small as 0.0003". My turbine ended up spinning up to 27,000 rpm when driven with compressed air, close to its bearing tolerances.