arranged two by two and diametrically opposite with respect to the axis of the jaw support and two adjacent grooves are offset from each other by an angle of substantially 90 degrees each of said grooves receives a jaw 18 able to slide in this groove for reasons of clarity only one of said jaws is shown in the figure in fig5 the jaw support 10 of the first tier equipped with four jaws 18 is shown surrounded by cam 12 in rest position the track 16 of this cam is conformed to cooperate with ends of jaws 18 to allow displacement of said jaws radial to the axis of rotation of the jaw support 10 towards this axis of rotation when said cam rotates about the jaw support in the direction of arrow f during crimping as shown fig6 at the end of crimping ends of jaws 18 lying opposite said ends of said jaws cooperating with track 16 are therefore moved into the hole to crimp the contact as shown fig8 the ends of jaws 18 cooperating with the track 16 are bevelled and a rotating element 30 is arranged between each bevelled edge and the track 16 the rotating elements 30 are not shown fig5 6 and 7 for the clarity of said figures the bevelled edge of a jaw 18 is made so that the distance between this jaw and said track is maximal at the rear of said jaw and minimal at the front the notions of front and rear being consideration in relation to the direction of movement indicated by arrow f of the cam 12 and hence of track 16 relative to the jaw support 10.