I bought an air variable capacitor from ebay. The old-fashioned metal kind with large interlocking plates. First time I've seen one.

But my problem is - there is no 'stiffness' in the shaft, so if you mount it the way the mounting screws imply, with the plates at right angles to the ground, then the plates don't stay in place when you let go of the shaft.

Is that normal? Or is there a way to tighten it? There's a screw at the pivot end of the shaft, but it cannot be tightened any more than it already is...

 

No its too loose,if its a Jackson type air capacitor there is usually a locknut at the end or grub screw, can you post some pictures please?

 

The end of the shaft away from the knob normally has a grub screw surrounded by a locking nut, which has to be loosened before the screw can be adjusted. Don't over do it though or the plates might touch.
Frank

 

Ah - thank you both very much! Loosening the nut allows the screw to be tightened - perfect. All working fine now - much obliged.