I suppose you could use a lathe, but most use a drill press with the propeller to turn mounted on a shaft and spinning. And then use a file to turn down to the right size. The best way is to put the file in a "X" "Y" vise so that you can slowly apply the file to the spinning prop. Hope I didn't confuse you too much. I think dragonfire said he used a 26mm Graupner prop for a 2mm shaft to turn down. Good luck.