I have a perfect-condition 1930 dash knob (marbelized amber color) that is stuck to a cut-off and rusted shaft. I've tried soaking the whole thing in a jar of PB Blaster for more than two weeks, but still have not been able to remove the plastic knob. Apart from cutting the shaft at the end of the plastic, and drilling the rest out, is there anything else I can try?
I've thought about soaking the whole thing in Coca-Cola (remembering my sixth-grade experiment of dropping a paper clip into a glass of the solution). Or, possibly a well salted solution... or even some type of acid. However, i do not want to ruin the knob, as it is so nice. Reproductions are no where near as nice.