I used to use the 1/4 nozzle successfully on my drywall router but hadn't learned how to do it before Use it on plastic boxes, even on metal cans I have found that I have torn the metal in places. I've tried different depths to find the right spot to get enough contact with the guide point, but maybe I'm just not feeling right because I can't follow the junction box very well. However, I'm no pro and they held up well to accidental hits on the screw.