There is apparently some confusion regarding the seams produced by Union Special® 36200 Flatseamers. If you are uncertain or just a bit unclear about such terms as Butt Seam, Lap Seam, Full Lap Seam, Single-Ply Trimming and Two-Ply Trimming, continue reading; this article will clarify things. In it we will discuss all the seams produced by our 36200s, as well as similar machines produced by our competition. And if you think you already know these terms, here’s a chance to test yourself!

First of all we will look at the Butt Seam - also called the Flat Seam - operation.

Butt Seaming

The Flat Seam (butt seam) as defined by ASTM booklet D6193 for Seam Type FSa–1, states “This type of seam shall be formed by seaming the edges of two or more plies of material with a row of stitches extending across and covering the edges of the material.”  In other words, the plies of material are butted and sewn together (in this case with a top and bottom coverstitch type 607). Hence comes the term Butt Seam.

A butt seam is sewn on 36200 Flatseamer machine styles 36200UA52, 36200UJ60, 36200UAE52, 36200UJE60 and similar older styles. To perform the butt seaming operation, the material is introduced into the presser foot opening, where the knife system then trims the left and right plies of material (also called Two-Ply Trimming) as it is fed into the machine.  The two plies are then laid down flat with the help of the presser foot with its particular shoe design, and sewn together with a 4-needle 6-thread top and bottom coverstitch type 607. The result is a stitch and seam type 607FSa-1, Figure 1.

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