This cap protects your BNC conector while not in use.

Turn the cap onto your BNC connector and tighten it firmly. It is held in place by taper friction, not by a bayonet spring (which would be difficult to print with PLA or PETG).

Print it with a small layer height (0.2 mm or less).

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Update 5 January 2026:
I made the internal grooves' angle shallower to increase friction effectiveness.

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As always I include the OpenSCAD source file for you to adapt and/or improve:

• Download and install OpenSCAD from https://www.openscad.org
• Launch OpenSCAD and open the enclosed OpenSCAD source file (/File/Open).
• Amend the parameters at the top of the file or even amend the code.
• Save your changes (/File/Save).
• Render the design (/Design/Render).
• Export the rendered design e.g. as a .stl file (/File/Export/Export as STL).
• Slice and print.

See my other designs at
https://www.thingiverse.com/thinger13/designs