I need to re-hang a sagging door (actually several). I've seen this question and answer, but wonder if my situation doesn't call for something a bit different. My issues: 1) its a heavy fire-door with a door-closer. 2) It is currently hanging completely on the door jamb. 3) Each hinge has 4 screw holes. 2 screws probably won't be able to bite the stud no matter what I do. For the other two screws I could probably get a minimum of 1/4-3/8 in clearance away from the edge of the stud if I angle the screws slightly.
I'm wondering if I'm just better off using machine screws with washers and nuts. I'm grateful for any advice.