Flat seams

The most common seams used are superimposed seams on two plies of fabric using a 514, four-thread overlocking stitch. Also, flat seams are used where two plies of fabric are butted... 

The most comphcated stitch type in this class is type 606, known as flat lock, which can be used to join fabrics that are butted together in what used to be called a flat seam. Type 606 is used on knitted fabrics, especially underwear fabrics. 

The flat-seaming stitch type 607 with nine threads (four needle threads, four looper threads and one top-covering thread) is used for trims and seams simultaneously, producing the flat, butted seams as on infant panties, men s briefs and other knitted garments (Figure 10.20). 

Figure 14.38 Extrusion welding a lap-type seam. Pressure is applied to the flat seam, and a hot air nozzle moves along the weld line ahead of the extruder. The hot air melts the thermoplastic in the weld area, and extruded material flows into the seam, forming a weld upon cooling.

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