Abstract: An arrangement for measuring the pre-tension of a threaded bolt having a central drill hole. A part is fastened to the lowest point of the drill hole and the difference in length of the part relative to the threaded bolt is determined via a length measuring device. An electric holding magnet, introduced into the hole, is fastened to a cable running from a cable drum and carrying an electromagnet, which, when excited, adheres to the closed hole at its lowest point; the cable is tightened and its length is held constant by a ratchet. The cable drum is movably supported on a tube connected to the threaded bolt in such a manner that, when the cable is loose, its carrier is pushed by a spring surrounding the tube against an upper flange on the tube; a length measuring device borne on the carrier contacts a surface of the tube. The measurement is performed with the cable tightened and its length held constant by the ratchet.

Abstract: Apparatus for measuring the pre-tension of a threaded bolt which is elongated by means of a tensioning unit and a screwed-in tensioning bolt; a measuring rod is inserted into a central hole in the threaded bolt and the difference in length is determined by means of a length measuring device.The measuring rod is guided in the housing of the tensioning unit, secured against rotation, and is threaded to engage a threaded bushing. The threaded bushing is longitudinally movable and secured against rotation in a bushing having external teeth. Rotation of the tensioning bolt is transmitted via gears to the threads on the measuring rod and converted into an up or down movement. The measurement may be made when the measuring rod comes to rest at the lowest point of the central hole.

Abstract: An apparatus for measuring the pre-tension of a threaded bolt by means of a two part measuring rod introduced into a central hole of the threaded bolt and of a length measuring device.The measuring rod includes an upper rod threaded to a lower tube which is secured against rotation. Rotation of the threaded rod by a motor moves the end of the measuring rod in or out of the central hole.