Summary

based on a screwthread library that is CC-By-CA but I can't find it anymore, so it's hard to attribute...

To attach lampshade to lamp fitting. Moertje_220.stl should fit, measured diameter of fitting is 20.5mm but that (and 21.5) is to tight. This varies from printer to printer.

Print in a material that does not melt or catch fire during use.