A form for a tuning inductor used in the output filter of a two vacuum tube ham radio transmitter

thingiverse

In making this radio, the instructions called for a classic air wound coil using 20 gauge wire spaced 16 turns per inch. My past experience is that getting this spaced coils to remain rigid is somewhat of an issue. So, I got to thinking that I could apply screw threading to basic coil form size and create ridges that would hold the coil secure. From there it wasn't much more effort to add mounting places for securing the coil to the radio. I also included a ridge that allows for a small microclip to be securely attached at any turn along the coil to adjust its inductance. Since you are not likely to need this exact inductor, I have included the OpenSCAD source so that you can create your own custom coil forms.