My idea is for loose and slipping setscrews used to secure pulleys, knobs, or hand wheels to shafts that don’t have flats for such purposes. When the setscrews just can’t be tightened enough to prevent the problem, I drop a short clipping of solid copper wire into the hole. The soft metal deforms and grips the shaft and the setscrew tip, preventing the screw from coming loose. I keep a short length of 8-gauge copper ground strap around for just this purpose.
The copper works better than any commercially available thread-locking liquid. I don’t get thread-locking liquid creeping under the component I’m attaching to the shaft, locking the component to the shaft. And, setscrews are easily removed when using the copper, so there is no risk of destroying their heads.
On-line name BadDog Wheaton, Maryland