It's tricky to get the thread/nut tolerances right, you may need to adjust it in the OpenSCAD file. The provided STL is for printing with the “0.15mm QUALITY” setting.

The model consists of a nut, a threaded rod, and a washer that goes on the inner side of the metal sheet it attaches to.

The threaded rod is designed to be attached with a M3 screw. It's OK if the nut is somewhat loose, it will be locked by weight of the cooker/whatever you use them for.

Feel free to remix