ORIGINAL: majortom-RCU
Walt, I appreciate the URL you provide, but that relates to servo mounting screws (which I do already use) and not for the screw that holds the servo arm to the servo hub, which is what zeeb is referring to. I will say that I've never had a problem with the servo arms coming loose from the hubs, but I still don't like the philips head, don't like the little star type lockwashers, and would prefer to use a socket head version, if I could get the right diameter & thread pitch.
The screws in the servo hubs can come loose. Had it happen on my first gasser recently. Luckily, my pre-flight check picked it up (not to mention a ball link nut coming off while idling).
I use Tamiya blue locktite, which seems to be popular with the local R/C car guys. It stays somewhat gummy and therefore won't just 'snap' loose. It's also easier to remove parts when you need to. It only goes rock hard (but still removable) after about 12+ months of exposure to the rigors of R/C planes.