The threads are not painted. The threads are cut into plastic. We evaluated nylon and metal screws. Nylon is no-go because they are too easy to strip the socket and we'd have to tap the threads first. So we use a self-tapping set-screw.
Since the screw is in plastic, everyone should be clear this is not a tone control for constant adjustment. The simple way to use it is if you want more, or less bass, turn the screw 1/4 rotation on each side and listen to several reference songs across a few genres. When you hear it the way you want it, leave it alone. The threads will handle a number of adjustments, but constant use could wear it out. The hex keys are included in the box and have a warning to this effect on the bag.
It works, it works well, but it's not for fiddling over and over and over.