Lap Seaming

The Lap Seam, in particular the LSa-1 type, is defined by the ASTM booklet D6193 as:  “This type of seam shall be formed by overlapping two or more plies of material a specified distance and seaming with one or more rows of stitches.”  In other words, the right ply overlaps the left ply and is sewn together (in this instance with a top and bottom coverstitch type 607).

A lap seam is sewn on 36200 machine styles 36200ACZ13, 36200UE52, 36200UE60, 36200UY52, 36200UY60, 36200UH52, 36200UM60, 36200UEA52, 36200UEJ60 and similar older styles. To perform a lap seaming operation, the material is introduced to the presser foot opening; the knife system then trims the left and right plies of material (also called Two-Ply Trimming, but for Lap Seam) as it feeds into the machine.  With the help and design of the presser foot, cloth guide on the bottom of the presser foot, presser foot shoes and lap former, the left ply is laid to the bottom and the right ply is laid on top of the left ply.  The plies of material are then sewn together with a 4-needle, 6-thread top and bottom coverstitch type 607.  The result is a stitch and seam type 607LSa-1, Figure 7.