Fixed-length tool

The utility model discloses a length fixing tool, which comprises a jacking mechanism, a floating mechanism, an elastic sleeve piece, a moving mechanism and a length measuring device, and is characterized in that the jacking mechanism comprises a jacking mechanism body arranged in a first direction and a first butt joint piece rotationally arranged on the jacking mechanism body around the first direction; the floating mechanism comprises a floating mechanism body arranged in the first direction and a second butt joint piece rotationally arranged on the floating mechanism body around the first direction. The first butt joint piece and the butt joint piece are axially connected through the elastic sleeve piece, and the elastic sleeve piece, the first butt joint piece and the butt joint piece jointly form a connecting structure rotating consistently around a first direction; the moving mechanism is used for loading the jacking mechanism body and the floating mechanism body and moving the jacking mechanism body a