i have a chinese lathe and there's some systems that doesn't work well when you carry relatively heavy work ,the clutch is one .
i've found a solution based on scrap parts , my English is a little rusted so i put pictures ,the first is the molding of the bloc
here the casting raw
this is the parts that drives the added clutch shell
i' ve made a new nut in two parts , one moved by the original system one by the added system
i hope that will be usefull