[3X24SPD]

I typically use Heat Staked threaded inserts from McMaster-Carr installed with a soldering iron for smaller stuff, but you can model a hole in a part and tap it.
For larger threads, you can model using a helical sweep. If you do a helical sweep on a 1.79 degree taper, you can print NPT.
I modeled and printed this filter assembly yesterday. It has 5/8-11 thread and 7/8-14 NPT modeled and printed.