Old telegraph equipment, including bugs and other landline equipment often has been abused at sometime during its life, resulting in bent screws. I've tried several ways to deal with this over the years, and think the best way to attempt to straighten bent screws is by screwing on nuts, equidistant both proximal and distal the bend, if you can get a nut past the bend. Put it in a vise, using the nuts as a fulcrum, with a 1/4" wooden board pressed on the 'hump' of the screw. Tighten the vise until it looks straight. I put a dot on the screw head as a reference point so I can identify the place where the bend is worst, and that's where the wooden board makes contact with the screw. Sometimes you need a second fine-tuning go-around. Usually you can't get it perfect but can always make it better than when you started. If it's badly bent, and you can't get a screw past the bend, using wooden strips as the fulcrum is an alternative. When it's just the head of the screw that's bent, putting the screw in a hollow standoff that's slightly larger than the screw diameter, tighten the outer standoff it in a vise, and hammer the screw head with a rubber mallet flat against the top of the standoff.