

https://www.sciencedirect.com/book/edited-volume/9780815515814/handbook-of-plastics-joining pirate this and read chapter 17 it’s really valuable
I actually prefer other kinds of fastening for pla. Magnets can be melted into undersized holes via a soldering iron (just avoid cooking too hot, keep it around 100 degrees).
Push fits and friction welds work well in certain applications.

If you have a vibratory tool you can join whatever since PLA melts so low but round shit you can put in a chuck will weld with a drill. They do wear down a bit though, so you need some extra material and you stop when it’s in the right place.