Nothing can ruin a restoration project faster than broken knobs. Sure, that old “boat anchor” ham rig will work just fine with some modern knobs, but few and far between are the vintage electronics buffs that will settle for such aesthetic affrontery. But with new old stock knobs commanding dear prices, what’s the budget-conscious restorationist to do? Why, fix the cracked knobs yourself, of course.
At least that’s what [Level UP EE Lab] tried with his vintage Heahkit DX60 ham transmitter, with pretty impressive results. The knobs on this early-60s radio had all cracked thanks to years of over-tightening the set screws. To strengthen the knobs, he found some shaft collars with a 1/4″ inside diameter and an appropriate set screw. The backside of the knob was milled out to make room for the insert, which was then glued firmly in place with everyone’s go-to adhesive, JB Weld. [Level UP] chose the “Plastibonder” product, which turns out not to be an epoxy but rather a two-part urethane resin, which despite some initial difficulties flowed nicely around the shaft collar and filled the milled-out space inside the knob. The resin also flowed into the channels milled into the outside diameter of the shaft collars, which are intended to grip the hardened resin better and prevent future knob spinning.
It’s a pretty straightforward repair if a bit fussy, but the result is knobs that perfectly match the radio and still have the patina of 60-plus years of use. We’ll keep this technique in mind for our next restoration, or even just an everyday repair. Of course, for less demanding applications, there are always 3D printed knobs.
This may turn out to be useful. I have an old piece of equipment in which one of the potentiometers was replaced at some point, and the new one’d shaft is not the same size as the original. I could replace that pot again, or shim the knob, but installing a new insert is another reasonable alternative. Especially if I wind up replacing the other four shafts, as is likely if I install more modern guts into this shell.
Tnx.
File a wee bit of flat on that shaft, you dont need to torque to a gadzillion foot pounds and the allen set screw plastic threads live a lot longer
Or countersink a small divit with a dremel.
I used candle wax to protect the screws sticking out at the bottom of the threaded inserts that I had to glue back into my laptop.
If you can drill and tap set screw holes into a heat settable insert, that would give you as nice amount of surface area for the adhesive to grab onto. You’d need to drill out the treaded part of the insert but that’s pretty easy going.
For a 1/4″ shaft, an inserts designed for a 1/4-20 should be fine or you could go 1/4-28 for a little more material to work with in terms of drilling out the threads. In the case of the 20 pitch, you mostly just need to drill out the threads as the major diameter should be pretty close to 1/4″.
I’d have goner that route since I have some of the inserts around. A lot of how you do it just gets driven by what you’ve got on hand or when you find a suitable solution – then you can stop looking and just get on with it.
Nice fix.
…presuming there’s a separate video concerning fixing the rotary switches and their increased resistance.
Nice hack.
You just reminded me of a Singer frequency generator that had a number of wafer rotary switches.
As they aged, contact cleaner would no longer help.
Just use the old knobs as greebles.