Abstract: This invention is concerned with manufacture of spring interior units using known machinery for the manufacture of hour-glass shaped spring members wherein a plurality of the hour-glass shaped spring members are conveyed to a locality whereat a plurality of said hour-glass shaped spring members are displaced in a form of a row located adjacent to another row of springs whence the two rows of springs are joined together at both their end convolutions and the process repeated until a spring interior unit with a predetermined number of rows of springs is formed automatically.