Stitch Density
Stitch density is a sewing specification indicating the number of stitches within a fixed length of seam, and is a control item related to seam appearance, strength, elasticity, and the load on the fabric.
Contents6 sections
Definition and Overview
Stitch density is the number of stitches formed per fixed length of a seam sewn by machine. In overseas specifications, stitches per inch are often expressed as SPI, and specification sheets usually state the measured length and the stitch type together.
The higher the number, the finer the stitches; the lower the number, the coarser the stitches. Even with the same setting, the actual appearance of the stitches varies depending on how the fabric is fed, the stretch of the material, and the adjustment of the sewing machine.
Relationship Between Thread Thickness and Stitch Structure
Stitch density is not an indicator of thread count or twist. However, with finer thread, dense stitches are easier to blend in, while with thicker thread or decorative thread, if the stitches are set too close together, the seam may look excessively dense or the fabric may pucker.
Depending on the stitch type, such as lockstitch, chainstitch, and overlock, the way the thread interlocks and its ability to follow stretch differ. For that reason, even at the same stitch density, seam strength, flexibility, and surface appearance cannot be compared in exactly the same way.
How It Is Written in Specifications and Main Applications
Stitch density is set for each sewing area, such as assembly seams, edge stitching, decorative stitching, and button attachment. The required fineness of the stitches differs depending on whether the area needs a neat appearance, seam strength, or stretch retention.
In specification sheets, it is important to specify not only stitch density but also the stitch type, thread used, needle, seam allowance, sewing direction, and tolerance. For fabrics that are prone to slipping, the seam allowance design and reinforcing tape are also considered.
- Decide whether to count from the right side or the wrong side.
- For decorative stitching, also check stitch uniformity and thread appearance.
- Before mass production, perform sewing tests on the actual fabric and check the condition after washing.
Selection and Sewing Notes
If stitch density is increased more than necessary, the continuous needle holes may weaken the fabric or cause puckering in lightweight materials. On the other hand, if it is too sparse, it may lead to insufficient seam strength, fraying at the seam allowance edge, and a rough appearance.
Adjust by combining fabric thickness, density, stretch, and surface texture with thread thickness, twist, needle size, thread tension, presser foot pressure, and feed conditions. In trial sewing, check skipped stitches, thread breakage, seam shrinkage, and seam stretch.
Differences from Similar Terms
Stitches and stitch count may be used to mean stitch density. On the other hand, sewing thread count is a way of indicating thread thickness and is a separate specification from stitch density. Fabric density also refers to the number of warp and weft threads in woven fabric, so it is distinguished from the number of stitches in a seam.
Knitting gauge is also a term related to how tightly the knitted fabric is constructed, and it differs from stitch density during sewing. When communicating specifications, clarifying whether the subject is fabric, knitted fabric, or a seam helps prevent misunderstandings.
Frequently Asked Questions
Is a higher stitch density always better?
A higher value may make the seam look finer, but it is not always appropriate. In lightweight or stretch materials, it may cause damage from needle holes, puckering, or reduced stretch. Decide through trial sewing according to the fabric, thread, and stitch type.
Are SPI and stitch density the same thing?
SPI is generally the English abbreviation for stitches per inch and is one way to indicate stitch density. However, stitch density is also used in a broader sense to mean the number of stitches per fixed length. In specification sheets, it is clearer to include the unit of measurement.
What should be checked to make stitch density consistent?
In addition to the machine feed setting, check thread tension, presser foot pressure, the combination of needle and thread, and the stretch and slipperiness of the fabric. Since differences can also arise depending on cutting direction and sewing direction, sew test pieces under the same conditions as mass production and measure the seams to manage them.
