How to install a cartridge bottom bracket (threaded) in threadless shell? Is it possible to install a threaded cartridge bottom bracket in a threadless shell which has a PF30 installed?
If you want to be able to install any ISO threaded BB, the way to do that is use a press-in adapter.



They have the disadvantage of not necessarily solving the creaking issues that might have gotten you to this point in the first place.

If you just want a simple way to run common 24mm or 24mm/22mm cranks, there are adapters that plug in to an existing PF30 or BB30 for that.

If the shell is metal and you want to run square taper, you can in theory get it cut to T47 and run a Phil Wood BB in it with their T47 cups. Despite being insane, this is the solution most likely to result in zero creak issues.