Here’s the solution to the sliding coil deteriorated bushing problem on the National NC-101X shortwave receiver. Unlike that other National products with “plug in” coils, like the HRO, the early NC-100 series use a “catacomb” coil assembly that slides inside the chassis to switch bands. A very ingenious design, and it works very well..for 80 years or so, and then the plastic bushings deteriorate from age and use.
The chances of finding new old stock bushings is slim to none, and even if they were available, they’d be just as deteriorated as the ones inside my receiver.
The solution, order a 1/2” to 9/16” bronze bushing from McMaster Carr, machine it down so the outside diameter is .512 inch, press in place using Loctite to retain, ream the ID so the shaft slides through the bushings freely.
I’d like to thank Marc KA2QFX for his very gracious and kind skills in the machine shop, machining the new bushings to fit properly into the sliding coil form.
After two long months, I can finally see the end of the NC-101 project in sight.