Abstract: Instead of a single headstock, two headstocks (12A,12B) are assembled one behind the other. Their spindles (14A,14B) have the same lengthaxis. The movements of the headstocks in the direction of that axis and for the opening and closing of their corresponding collets are controlled in such a way that while one of the headstock advances the material bar (M) with closed collet, the second headstock returns to its start position with open collet. During the transition phases both collets are closed. The main advantages are: the separate material feeding system is no more necessary and the dead times required for returning the headstock are suppressed.