I am working on a personal project at the moment with similar issues (a dock ladder that folds).
I haven’t viewed your .skp, but this would be a general process:
In the .skp model, create a centre axis for the bolt with a guideline. (in your version of SU, may require editing the bolt - finding the centre of it by drawing a line across its diameter).
You can then use the rotate tool to rotate (type in your prefered rotation angle once you engage the tool) the required components (after selecting all items you want to rotate and make a group or component).