The Tech Pack Designer’s Stitch and Seam Specs

In the garment development stage, the tech pack for clothing acts as a manual for taking each step. The manual guide explains each stitch and seam specification in the garment. The 2D shapes illustration shows where the seams start and end structurally. This eliminates ambiguity at each step of the production. Errors may ruin the whole production shipment.  The whole shipment is prepared in a well-documented manner. In this way,  errors are avoided in the production process. 

The Science of Stitch Classification

The stitches are not just “straight” or “zigzag” in pattern; it is their exact position. The tech pack for clothing uses ISO 4915 standards to specify the thread and its exact position in the garment.

• Class 301 (Lockstitch): Lockstitch is used for woven garments and is commonly used for a precise stitch. It looks the same on both sides after the stitch. Highly secure, but has zero stretch.
• Class 401 (Chainstitch): It is a heavy-duty seam normally used for jeans. Chainstitch offers high strength to avoid rupturing. It is slightly more flexible than a lockstitch.
• Class 504 (Overlock): The Overlock is essential for knits (like T-shirts). It can stretch with the garment, so the whole garment is not torn apart. So the fabric prevents the edges from fraying.

Seam Architecture (ISO 4916)

The architect of the eam is another thing which must be specified in the booklet. The way pieces of fabric are layered together depends on the strength of the seam. It is just as important as the stitch itself during the production stage. The Tech Pack Designer for clothing selects a seam style class based on the garment’s function, as all depends on the garment’s use.

• SS (Superimposed Seams): The standard side seams are placed on the two pieces laid on top of each other. So the stitch does not appear on the garment itself.
• LS (Lapped Seams):  The lapped seams are done by placing the two pieces overlapping or over each other. This is commonly done in denim to provide “felled” strength.
• FS (Flat Seams): The flat seam is done by placing the two pieces butted together / it is covered with a flatlock stitch (standard in activewear to prevent skin chafing).

Professional Stitch & Seam Specification Table

Seam/Stitch Location	Seam Type (ISO 4916)	Stitch Type (ISO 4915)	Stitches Per Inch (SPI)	Technical Note
Side Seams (Woven)	SSa-1 (Plain Seam)	301 (Lockstitch)	10–12 SPI	Press open; clean finish edges.
Leg Inseam (Denim)	LSc-2 (Felled Seam)	401 (Chainstitch)	8–10 SPI	High-strength durability spec.
Neckline (Jersey)	BS (Bound Seam)	406 (Coverstitch)	12–14 SPI	Use a 10mm binding strip.
Activewear Legging	FSa (Flat Seam)	607 (Flatlock)	14–16 SPI	Four-needle, six-thread setup.
Hemming	EFb (Edge Fold)	103 (Blindstitch)	8–10 SPI	Invisible stitch for a formal finish.

Take Away:

The specifications define the exact mechanical process repeated several times. The code of the booklet is written using international ISO or ASTM classifications. This eliminates any chance of human error in the production stage of garment stitching.