a machine for blending , matting , shortening or sizing natural or artificial fibers , in which the work is performed by groups or trains of three rollers . a first working stage has a single head delivering two slivers and in which the twin bearing rollers are of large size , the two slivers emerging from the single head being fed axially or perpendicularly by directional and juxtaposing members towards a second working stage in a single lap , the width of which is at least 50 % less than the width of an individual sliver . the second working stage has a reducing head which comprises a plurality of trains with twin lower retaining and traction rollers , respectively , mounted overhung on frames , adjustably spaced from one another .