Sewing machine technique: seams, stitches and material selection
How to choose nails, thread, and needle so the seam holds on both fabric and leather
An upholstery can be perfectly built in all its layers — but if the seams don't hold it falls apart. Sewing is therefore not just a finish it's a structure in itself that must withstand pull tension and years of daily use. Knowing your seam types thread and needle choices and classic errors is therefore just as important as knowing the upholstery's layers.
§The most important joint types
Different tasks call for different seams. A double seam (two parallel rows of stitches) is used where the seam must withstand extra pulling for example on edges and corners that are heavily stressed. A French seam — also called a closed seam — hides the raw edge inside the seam itself and is used where the edge must be both strong and nice to look at among other things in leatherwork. A hidden seam is used where visible stitches are not wanted for example with finishes and binding tape. An overlock seam cleans and protects the fabric edge against unravelling before it is sewn together with the rest.
- 01Double seam — extra strength at corners and stressed edges
- 02French seam/French seam — hides the raw edge, strong and neat, typical for leather
- 03Hidden seam — invisible stitches at endings
- 04Overlock stitch — edges and protects the edge against fraying
§Thread by material
The thread choice must match the material. Polyester thread is strong, elastic and UV-resistant and is the standard choice for most upholstery and covering fabrics. For leather and artificial leather that are subject to hard pulling and wear — such as car seats — a stronger core yarn thread is often used, which has both strength and some elasticity, so the seam does not break when the material works. Cotton thread is used less often in modern upholstery because it is weaker against wear and moisture than synthetic threads.
§Needle and stitch according to material.
The needle should match the material it goes through. A common pointed needle is used for woven fabrics while a leather or wedge needle with a sharp wedge-shaped point cuts through leather and artificial leather without tearing the fibres. Stitch length is adjusted for material thickness – too short stitches can perforate and weaken thick leather while too long stitches give a loose and weak seam on thinner fabric. Thread tension must be set so the seam neither ripples nor pulls the material together.
| Material | Needle type. | Typical wire choice |
|---|---|---|
| Furniture fabric | Point chiseling | Polyester thread |
| Leather | Wedge needle (cutting tip) | Strong core yarn thread |
| Artificial leather | Wedge needle or universal needle | Polyester or core yarn thread |
§Common errors – and how you correct them
Good sewing technique is not something you learn from a manual alone — it requires practice on scrap pieces before you set the machine to the finished upholstery. Take time to test stitch type, thread and needle on a piece of the current material before you sew for real. It is cheaper to discard a test piece than an entire upholstery.
“A seam is not seen when it is sewn correctly — but it is felt immediately if it is not.”