When the set screw is stripped, the set screw head is damaged, and you cannot use a screwdriver to make a grip on it. In this case, a screw extractor is of great help. But, you must have the right size screw extractor. To remove the handle, begin by drilling a hole into the center of the screw. Then, fit the screw extractor into the drill hole. Use a hammer to tap the extractor gently for a better grip. On the top of the extractor, fix the adjustable wrench and turn it slowly. That way, it will remove the stripped screw.