[ARC5] Stuck set screw

[Robert Nickels]

My worst experience was with a Hallicrafters HT-20 transmitter that had 
been stored in a damp basement - lots of knobs, two set screws each, and 
not a one would budge.   I finally set up a carbide drill bit with a 
depth stop so I wouldn't drill into the shaft and drilled each one 
out.   As Mike says, you have to use a carbide bit - either a long bit 
or with an extension, and take your time.    In my case, even after the 
set screws were drilled out the knobs still would not come off because 
of the corrosion. I was fortunate in being able to access the shafts 
behind the front panel, where I could clamp each with a needle-nose Vice 
Grips.   Then I wrapped each knob with cloth and tape to protect the 
knurled surface and used another pair of Vice Grips to gently break the 
knob loose from the shaft.   In most cases I still had to "thread it 
off", but as long as you can minimize the strain on the pot or switch 
you can apply pressure without too much fear of damage.     I tried 
every penetrant on the shelf and didn't have any success with any of 
them but for those who are interested in comparisons of your favorite, I 
recommend Canadian YouTuber "AvE"'s humorous and slightly R-rated 
review, with actual comparative test data:

https://www.youtube.com/watch?v=YeTNXbDbHcM

The fun part was drilling out and retapping the knobs for the next size 
larger set screws and making the transmitter look like new after getting 
the front panel repainted and silk screened.

73, Bob W9RAN