In the previous papers, the authors proposed a method to obtain the most proper fastening force caused by nuts for a given bolt and external repeated load, showing some examples. It was also made clear by those examples that tension bolts have not so much strength as normal bolts. A method for graphical determination of the strength of bolts under repeated load was also stated. In this paper, they carried out a method to calculate immediately the most proper fastening force so as to induce the maximum amplitude of the external load under various mean external loads. A graphical method was also carried out. Moreover, they carried out a method to calculate the most proper fastening force for the purpose of preventing the oil leak between flanges comparing with the proper bolt connection with numerical examples.