and are at a distance from one another given suitable shaping of the spacers 34 35 both the correct angular offset and the correct distance apart is obtained automatically between adjacent leaves so that the embossed leaves 33 can be assembled in a simple manner to form stacks and can then be immediately welded in the case of the spacers 34 35 shown in fig8 four contact lines 37 depicted as broken lines are obtained along which the electron beam welding can be carried out the configurations shown in fig6 8 relate to leaves having integral spacers however similar concepts can be applied just as easily to leaves having separate spacers the use shown in particular in fig8 of spacers designed in this way has a number of advantages firstly the angular offset can be set exactly from leaf to leaf as a result of which the need for the leaves to be put together exactly is reduced secondly as clearly shown in fig8 there are numerous lines on which the electron beam welding can be focussed in order to produce acceptable welding with little disturbance as already mentioned the leaves according to fig8 can be formed by a method such as embossing for example the embossing permits the production of features which emerge from the surface this having more than one advantage with a.