Abstract: A carriage-mounted sewing machine with special stitch forming means and an advance power trimmer are driven as a unit along the rails of a railway sewing machine bed by operation of the sewing machine motor and a unique clutch arrangement coupled with the carriage train drive for the railway bed. The stitching mechanism features an improved looper arrangement whereby precisely the necessary degree of slack is produced in the butt seam stitches to enable the spliced carpet sections to "butt out" perfectly without a gap and without overlapping at the butt seam or buckling. A specialized presser foot and throat plate arrangement allows the butt seaming of carpet sections up to two inches in total thickness. Carpet scrap is reduced to a minimum.