I wanted an airtight PC4 feedthrough for my drybox, so i took some insperation from the RoboMagus solution and iterated to this solution.
The cap is capable of sealing the whole feedthrough airtight, when it is not in use. I also added a filament stopper that fits under the cap to be able to connect the system without opening the drybox.
It works fine with PC4-M6 and PC4-M10 connectors from Amazon. I found out that the thread is actually an BSP G1/8-28 thread for the M10 connector, as the pitch of the thread wasn't M10. The PC4-M6 connector has an M6 thread in this model. I also added a Nut for real M10 PC4 connectors (that also exist).
The feedthrough is glued to the outside of the box with 3M VHB double sided tape and the connector is held in place with the M6/M10-Nut. I drilled 10mm holes and aligned them with the hole of the feedthrough when glueing and that is basically it.
Also check my desiccant box that is pictured in these pictures:
https://www.printables.com/model/290383-ikea-365-108l-sliding-desiccant-container-for-dryb
The author remixed this model.
same idea but with screw on cap.