Measuring tool for detecting length in cavity

The utility model discloses a measuring tool for detecting the length in a cavity. The measuring tool comprises a rod body, the right end of the outer side of the rod body is sleeved with a no-go gauge head, vertical grooves are formed in the upper side and the lower side of the right end of the rod body, a transverse groove is formed in the rod body, the vertical grooves communicate with the transverse groove, locking seats are slidably connected into the vertical grooves, locking grooves are formed in the upper wall and the lower wall of the interior of the no-go gauge head, and the locking seats are connected with the adjacent locking grooves in an inserted mode. The side, close to the center of the rod body, of each locking base is provided with a sliding column, the end, close to the center of the rod body, of each sliding column is provided with a conical base, the interior of the transverse groove is slidably connected with a jacking base, and the jacking bases and the conical bases are installed in a