hole 15 is modified in this case the modification amount of the pitch of the screw thread 18 of the remaining space portion 16 is determined by a thickness t of the stopper 20 of the press tool 21 and the pitch of the screw thread 18 of the pressed remaining space portion 16 is preferably modified to be equal to about u2153 of a pitch of a screw thread 17 of the screw hole 15 in this case the caulking guide portion 19 of the press tool 21 is fittingly inserted into the wrench hole 10 a after passing through the remaining space portion 16 and thus the caulking position of the press tool 21 around the center of the screw hole 15 can be accurately secured and a striking force of the hammer can be maintained uniformly during the caulking of the press tool using an impact hammer leading to an increase in the precision of the modification of the pitch of the screw thread 18 of the remaining space portion 16 during the caulking as a result of a modification test of the pitch of the screw thread 18 of the inlet portion of the screw hole 15 after the set screw 10 is fasteningly.