When drilling a hole in wall to put up shelves I have encountered the same problem twice with two different drills: the drill assembly which holds the drill-bit unscrews itself from the main body of the drill whilst I am drilling leaving the drill-bit and assembly sticking into the wall while the main part of the drill, still in my hands, comes away completely. There's a long screw inside which holds the two parts of the drill together which seems to have worked itself loose but even when I try to screw it back together I get the same problem.
I chucked away the first drill as it was old and cheap and borrowed a new one from a friend, but I've got the same problem! Am I doing something wrong or is this a common problem with cheap drills?
Thanks.