Abstract: | The static durability of the threads is settled by iso rules and determined by the test of turn tearing onthe bolt.The fact that the threading by deformation insure to the threading turns a continuos fibre unlike the basismaterial insures a growth of the durability comparing to the threads obtained by splinteringThe process of thread deformations, leads to a greater concentration of the steel pearlite grains under thepression of deformation, ( it is realized in this way a thickening of the pearlite grains ). Consequently thereoccurs a general deformation of the chrystal grating of the deformed metal layer, that influences the quality ofthe piece |