line position of fig1 the threads as they are forced into the entrance portion 22 of the die 21 are progressively deformed or crushed with the crests of the threads cold flowing into the alternate valleys see crushed threaded section 26a as the first threads 26a substantially fill the straight die portion 23 a desired holding tension in the rod 13 is reached and the load is supported the entire internal length of the die 21 including the entrance portion 22 and the straight die portion 23 has an interference fit causing the deformation of the threads 26a the surface engagement between the die 21 and the crushed threads 26a establishes a frictional holding interface to provide the desired tension in the bolt assembly when tensioning the bolt assembly 10 an initial threshold level is selected that is clearly within the elastic limit of the rod 13 this lower limit and the fact that there is substantially no torque forces involved maintains the rod 13 at a tension where fatigue is minimized the rock is held under normal conditions and then under emergency conditions caused by separation of rock as shown by developed fault f 1 in fig2 there is an increase in tension and a resultant yielding of coupling 14 to allow the rock to sag the relative sliding movement in the coupling 14 prevents any significant increased tension and consequently of course maintains that tension well within the safety.