[Modges'66]

And now, without further adieu, on to the fabrication of the heater control knobs!
I started with a piece of aluminum big enough to yield 5 knobs from, in order to have a backup plan for screwing up a few in the process. NOTHING ever goes as planned in your mind!
Once that I was pleased with the profile of the knob shape, I drilled & tapped #10-24 holes in the bottom of the knob profile that would be used to retain the knobs onto the levers of the control. Then, through the center of each tapped hole I milled a 3/32" slot for the control lever to fit into.
So as you will see, the threads on each side of the slot hold the setscrew that retains the lever.
Pretty simple really...NOT!
Once that all of this was completed, I separated the knobs from the workpiece by sawing them & machining the sawed surfaces to size.
I then milled a groove into the face of them with a 3/16" ball nosed cutter, and polished the individual knobs!

I didn't even screw one up!...yet.