Abstract: The forming simultaneously of a series of cylindrical metal belts in a range of slightly different measures suitable to be fitted into each other into a multiple layer driving belt. The belts are formed from a series of blanks of tubular material, having the same diameter. Two parallel rotatable rolls, having a length exceeding the total length of the series of blanks are inserted through the series of blanks which are positioned side by side along the said length. One of the said inserted rolls is a stretch roll having a relatively small diameter with respect to a pair of work rolls of large diameter between which the tubing-stretch roll assembly is engaged in a position offset to one side of the plane containing the axes of the said work rolls.