Overedging explained: techniques, stitch types and thread selection
In practice, little attention is often paid to overedging. However, it has an important function and, together with other processing details, it determines the appearance of the inner garment.
Hardly any textile can do without overedging. Clothing, home textiles and even some technical textiles require finishing to protect the sewn edges from fraying. From the finest silk fabrics and coarse denim to tight-fitting sportswear and technical filters, the materials and products vary greatly, as do the requirements for perfect overedging. The choice of the right sewing thread is particularly crucial for successful overedging.
There is hardly any other seam that offers as many possibilities in terms of sewing thread selection as overedging. Serging should be tailored to the material, model and area of application, as well as the desired look and function. Overedging gives the interior a attractive appearance and is a sign of perfect workmanship. It therefore makes sense to review your current sewing thread concept and adjust it if necessary.
Selection of processing parameters
Selection of processing parameters plays a key role in achieving high-quality overedging results. Parameters such as stitch type, stitch density, thread balance, and seam width must be carefully adjusted to the material and application. Only a well-balanced setup ensures consistent seam appearance, reliable edge protection, and efficient production.
The following stitch types are suitable for classic overedging, i.e. securing the edges of the fabric against fraying:
2-thread overedging
In practice, the most commonly used stitch types are interlooped at the stitch hole (stitch types 502 and 504). Attaching the needle thread loop directly to the stitch hole has advantages in terms of correct thread balance and smooth processing of the fabric edge without curling. The most common is 3-thread overlocking (stitch type 504). Stitch formation with three threads offers the best conditions for a flawless stitch pattern, even with difficult fabric qualities. The 2-thread overlock is often used on the assumption that it requires significantly less sewing thread. However, the difference is not that great: stitch type 502 requires approx. 10% less sewing thread than stitch type 504 for the same stitch density and seam width.
In some cases, overedging is also carried out in a single operation with the production of the joining seam. For this purpose, 4-thread overlock seams, stitch types 512 and 514 (see illustrations below), or the classic safety seam (stitch types 401 and 504) can be used. In these cases, the durability and seam strength of the closing seam must be guaranteed. This usually means increasing the stitch density to at least four to six stitches per cm (depending on the application).
4-thread overedging
The correct thread balance of the needle and bobbin threads is important for a good appearance of the overedging. In practice, however, the serging seams often neither show interlooping at the needle hole nor on the edge, but something ‘in between’. This makes the seam appear uneven and untidy. Furthermore, this can lead to the seams showing through when ironing.
The stitch density determines the degree of cut edge coverage. In the clothing sector, a stitch density of 4 stitches/cm is standard. Fabrics that fray easily often require better coverage and therefore a higher stitch density. The same can apply to garments that undergo demanding industrial laundering after manufacture. In this case, practical tests must be carried out to determine the required edge protection. Fabrics that do not cause problems can also be serged with a lower stitch density.
Upholstery fabrics are often serged with a stitch density of 2.5–3 stitches/cm. For fine curtains, on the other hand, a stitch density of 4 stitches/cm is standard practice. Due to the wide variety of products and materials, there are no universal standards for technical textiles.
The stitch density influences thread consumption and thus also the sewing thread costs. A change in stitch density from 3 to 4 stitches/cm increases thread consumption by approx. 20%. Here, it is important to balance quality requirements (e.g. optimal coverage effect) with financial specifications.
The following diagram shows the influence of stitch density on thread consumption for the common overlock stitch type 504 compared to stitch type 301, which is used for closing seams.
Random samples of garments often show varying stitch densities at different seam positions. In addition to the unattractive appearance, this also makes it difficult to position the sewing thread precisely.
The seam width is determined by the machine design. 5 mm is the standard width. In accordance with the guiding principle ‘as wide as necessary, as narrow as possible’, this measurement has become established for almost all overlock machines. The seam must be wide enough to ensure secure edge coverage without the risk of tearing. On the other hand, the seam should be narrow enough to keep seam application and thread consumption to a minimum.
There are exceptions to every rule: with a rolled hem (using stitch type 504), the seam width is usually just under 2 mm.
Very sturdy fabrics, but also materials that fray easily, rarely forgive a blunt knife on the overlock machine. The result is then extremely unattractive. For this reason, it is important to ensure that the knives are intact and sharp.
Sewing thread selection
There is more than just one good choice. But how do you achieve the best result in each case? The following criteria serve as a guide for selecting the right sewing thread:
The appearance of the interior is determined by the sewing thread construction and size. Fine continuous filaments create an almost invisible, delicate seam finish, which is particularly desirable for fine fabrics. Textured multifilaments and microfilaments, on the other hand, cover the seam edge perfectly with their voluminous character. This is particularly useful for materials that fray easily. Core spun threads can be used for both closing and topstitching seams as well as for overedging, offering the advantage of universal applicability – keyword: single-thread concept.
For sportswear and other skin-tight garments, the feel of the seams is the main factor in determining the sewing thread concept for overedging. Due to the individual nature of the material, there is no universal recommendation for ‘soft seams’. Only seam comparisons can determine the best solution here. All potential sewing thread concepts and sewing parameters should be tried out.
Not all types of sewing thread are equally suitable for all overlock machines, and not all types of sewing thread are equally suitable as needle and looper thread. This has an impact on sewability and sewing safety. Texturised continuous filaments (also known as bulk yarns) are more open, less compact and have a lower thread closure due to their open construction. This can be disadvantageous for the stresses involved in the sewing process, especially for the needle thread. In practice, bulk yarns are therefore often used as looper threads in combination with core spun threads as needle threads.
Furthermore, the properties of the selected sewing threads have an influence on internal goods transport. Texturised continuous filaments, for example, tend to snag more easily (e.g. on rough surfaces) due to their open structure. These individual filaments pulled out of the thread are called pulled threads and should be taken into account when deciding on the sewing thread concept.
Furthermore, the overedging must not cause any difficulties during ironing. Delicate, fine fabrics often show iron marks as a result of overedging. The seam presence and thus the tendency to show iron marks depend on the type and size of the sewing thread, but also on the fabric and processing parameters. For critical fabrics, tests should be carried out before production begins in order to select the best sewing thread.
Laundry articles place special demands on functionality during processing. Here, the overedging must not be damaged by the (industrial) washing process, e.g. for leased articles. Core spun threads offer the best conditions for high mechanical stress during washing.
The purpose of overedging is to protect the edges of the sewn fabric from fraying. If we follow the rule of thumb ‘the stronger the edge coverage, the higher the protection’, it becomes clear that not all types of sewing thread are equally suitable for this task. Bulky bulk yarns inevitably provide better coverage than delicate multifilament yarns or core spun threads. Depending on the fabric quality, i.e. depending on the tendency to fray, this criterion has varying significance. For fabrics that fray heavily, this argument alone can determine the choice. For fabrics that fray less, this criterion is irrelevant.
The aforementioned tendency of serging seams to leave iron marks is also important in later use.
The various sewing thread concepts for overedging differ not only in terms of feel, appearance and function, but also in price. Due to the simple production process, bulk yarns is naturally cheaper than twisted yarns. Due to their high thread requirements, serging seams often account for the majority of total thread consumption. The cost of serging threads therefore has a correspondingly large impact on the total sewing thread costs. However, sewing thread costs only account for a small proportion of the total cost of a garment. Switching to a higher-quality serging thread therefore usually only leads to a minimal increase in costs.
In addition to the pure procurement costs, production performance must also be taken into account for a correct cost estimate. Sewability and the number of corrective actions required (or the occurrence of second-choice parts) are important here and have a significant impact on productivity.
Limiting the colours of sewing thread for serging seams, for example to four basic colours, can save costs. Fewer colours mean less planning effort, lower stock levels, higher productivity due to less frequent colour changes on the sewing machine and, in some cases, lower purchasing costs due to larger order quantities. However, in this case, one must accept poorer colour matching of the serging to the fabric. For some manufacturers, this is unthinkable, while for others it is acceptable or even a desired design feature.
If you want to limit the number of colours, finishing with fine multifilament threads such as Serafil fine 300 offers particular advantages: the semi-transparency of this sewing thread size ensures the best possible colour match between the serging and the fabric. This is often aptly described as the chameleon effect. This effect makes it possible to minimise the colour selection in production facilities, especially for the serging seam. With a colour selection of four to five colours, most colourful materials can be processed.
The Serafil colour card contains several colours that are specifically designed to cover a wide colour spectrum.
| Colour no. | Colour | Colour of the outer fabric | |
|---|---|---|---|
| 1000 | Natural white |  | all white shades, light pastel, very bright colours, uni or patterned (e.g. bright beige, grey, green, blue) |
| 326 | Light beige |  | light through to medium colours, uni or patterned (e.g. light beige, grey, blue) |
| 329 | Dark beige |  | stronger, darker colours, uni or patterened (e.g. strong grey, brown, blue) |
| 4000 | Black |  | all dark colours |
The following table provides an overview of sewing thread concepts and a description of their properties.
| Construction and raw material of the sewing thread | AMANN article | Characteristics |
|---|---|---|
| Polyester / polyester core spun | Saba 150 Saba 120 Saba 100 Saba 80 |
|
| Polyester continious filament | Serafil fine 180 (120/2) Serafil fine 300 (200/2) Serafil fine 420 (300/2) |
|
| Polyester continious filament texturised | Sabatex 100 Sabatex 120 Sabatex 250 |
|
| Polyester microfilament texturised | Sabasoft 120 |
|
Application examples
There is no silver bullet for good overedging. In most cases, different sewing thread concepts are functionally suitable. Serging with bulk yarns or continuous filament varies greatly, but both concepts can be the right solution for the same task. The decisive factors for the choice are then the desired appearance, the area of application and the costs.
The following table shows typical solutions and proven concepts:
| Application | Main focus | Stitch density | Needle thread | Bobbin thread |
|---|---|---|---|---|
| Lingerie | Covering | 5 stitches / cm | Sabatex 120 | Sabatex 120 |
| Soft | 5 stitches / cm | Sabasoft 120 | Sabasoft 120 | |
| Jeans | Robust | 4 stitches / cm | Saba 80 | Saba 80 |
| Classic HAKA trousers | Filigree | 4 stitches / cm | Serafil fine 180 (120/2) | Serafil fine (120/2) |
| Silk blouse | Fine & noble | 4 stitches / cm | Serafil fine 300 (200/2) | Serafil fine 300 (300/2) |
| Mattress plates | Economic, efficient | 3.5 stitches / cm | Topfil 80 | Texturan 120 |