The correct Thread Tension
How the correct thread tension influences the seam quality- Are you annoyed of loose stitches, poorly pulled in yarn or even seam ruffles. In this article you will find the solution for these sewing machine problems.
This article is an excerpt from the book “Atelier – Fachwissen aus der Praxis Teil 1“. Further information and instruction for textile design can be found in this book.
What is the Thread Tension?
Each sewing machine has at least one thread tension- in this case it is a single- thread sewing machine, e.g. simple chainstitch, blind- stitch or similar stitches. The lockstitch machine has two thread tensions, because each thread must be braked individually and can be adjusted separately. In this article is restricted to the lockstitch because this is the most important type of seam stitch and is usually responsible for a variety of seam ruffles, which are among other issues caused by thread tension- the expert speaks of tension ripples. The yarn has to be slowed down during the run from the bobbin to the seam. Sewing machines have basically four tension devices: the thread guides, the tension discs, the tension regulator for the upper thread and the case spring for the bobbin thread.
How does the Thread Tension work?
In industrial and most crafting machines, the upper thread tension is at the front and consists of two small discs which are compressed by a spring. Usually a rotatable cap is attached at the front. When adjusted to a higher number (turned right), the discs move closer together and increases the amount of pressure. Turned to a lower number (turned left), the discs move apart and decreases the pressure. Household sewing machines often, have a covered thread tension, only a wheel, on which the correct thread tension can be adjusted is visible. This is a good solution for the appearance, but the dirt can only be removed by a specialist. For industrial sewing machines, the yarn must be steered over a screw or spring called the thread take- up spring. This thread take-up spring should cover a distance of 4 to 6 mm and rest when the needle pierces into the fabric.
The spring compensates the inadequacy of the sewing machine – What the sewing machine defines over the thread lever on sewing thread is not exactly what is needed for stitching process, this is compensated by the thread take- up spring. The bobbin thread must must be slowed down as well. It runs under a small plate on the bobbin case. The throat plate usually has two screws. The screw at the end holds the plate, while the screw lying towards the center allows a different pressure and therefore a different tension of the thread.
Adjusting the Correct Thread Tension
Starting point is in each case is the tension of the lower thread. Wind the bobbin of the lower thread, insert it into the capsule and pull out the thread under the tension spring. Grasp the thread end and let the bobbin hang down with the capsule. If you now move slightly up and down, the bobbin should slide down with the capsule. This would be the tension of the lower thread set correctly – at least theoretically. If the bobbin case doesn’t slide down or slides down immediately, the thread tension must be adjusted. In either case use a small screwdriver to turn the screw clockwise (to a higher number) or counterclockwise (to a lower number). Now adjust the upper thread tension.
To make the basic adjustments, select contrasting colors for the upper and lower thread and a contrasting fabric, in order to recognize the stitch entanglement. The interlooping of the thread should be in the center of the material, i.e. neither visible on the upper nor on the underside. Of course, this only works if the fabric is not too thin, so do not necessarily choose the thinnest fabric for the adjustment. If the needle thread is too tight, it will pull up the bobbin thread and the interloops will be visible on the upper side of the fabric. If this is the case, then loosen the needle thread tension, but avoid adjusting both needle and bobbin tension. Thread looping on the underside of the fabric is always an indication that the upper thread tension needs to be tightened by turning it clockwise. The thread tension of the machine would be optimally adjusted, after this process.
The correct Sewing Rhythm
The seam is even and smooth, then again it forms loops on the underside and sometimes on the upper side. Do you sew evenly? If you have adopted the frequently, in the industry practiced rhythm of jerky stitching, then the seam can not become even. When you slow down the machine, the lower bobbin runs after, with further sewing the first stitches on the upper side are entwined. Either you change the way you work by sewing evenly, or you need to increase the bobbin thread tension and then the tension on the upper thread to get a consistent stitch pattern. However, this is at the expense of the seam quality, as higher yarn tensions stress the sewing thread more, i.e. they have less seam strength and less seam elongation.
However, with thin fabrics the the seam puckering caused by the unnecessarily stretched sewing thread is even more important. You can’t sew longer seams without detaching and therefore have to work forcibly jerky? Then your sewing speed is certainly set too high. The sewing speed should not be as high as possible, but should be chosen as necessary. For modern sewing machines, there are appropriate adjustment electronics, in the older machines, a smaller drive wheel attached to the engine and already runs the sewing machine slower.
Guiding the Thread to the Needle
Have you ever looked at how the thread spool stands on the sewing machine? Household sewing machines are easier to handle than industrial sewing machines, where the thread is pulled upside down and the spool stands. The spool isn’t set in correctly because you don’t have a suitable thread spool pin? These pins are very important, because only with a vertical stand of the spool, the sewing thread can run smoothly without being braked. Does the thread also runs vertical into the thread guide eyelet on the thread stand? The sewing machine specialist speaks of the “gallows”. Usually several openings are attached at this gallows. The right one is the one, above the spool. The gallows must be exactly above the spool and not pushed away to the side.
What happens if the thread is led through a missing pin or incorrect position of the gallows? The seam becomes uneven because the thread can not slide off the spool properly. Under certain circumstances, the sewing thread may even break, which is doubly frustrating. It should also be mentioned that the attachment direction for the sewing thread is very important. When flowing upside down, the rotation of the sewing thread is changed. If the thread runs off clockwise, the existing rotation is increased and the thread becomes restless. When the thread runs counterclockwise, the rotation is reduced and the thread calms down. Under certain circumstances, the thread can become so restless that curls form, leading to uneven stitch insertion and even thread breakage. Usually, a spool should be printed so the thread runs properly if it is attached correctly.
Smoothen the Thread
The thread runs from the gallows of the thread pin into the sewing machine. It’s guided through different eyelets, also known as “thread smoother”. This should prevent the sewing thread, which is pulled back jerky, from collapsing possibly intertwining or even breaking. The thread lifter moves the direction of the needle, where the thread is e.g. is passed through an eyelet so that it runs vertically into the needle. This ensures that the sewing thread is protected in the long groove. If the eye of the needle is bent, broken or not threaded, it happens quickly that the thread runs from the side into the groove and the seam becomes uneven.
If you sew, you should also take care of your sewing machine. The more you sew, the more lint sifts into the guts of your machine. Therefore it’s really important to clean your sewing machine once in a while. This particularly applies to the area under the throat plate. Unscrew the plate and use a lint brush, canned air, or vacuum to remove the lint. Since the lint absorbs oil like a sponge, the hooks are often “dry”, which can be recognized by the heating of the machine. A drop of oil should be placed on the hook after cleaning. Lint and thread ends under the throat plate, or around the bobbin case and bobbin, increase the resistance and restrict the thread flow or may even lead to the “death” of the hook when it has become too hot. Depending on the sewing machine you have to pay over 50 Euro for a new hook, which must be inserted by a specialist. A new hook must be adjusted and timed with the needle,otherwise it can run restlessly and strain the sewing thread. That’s why sewing machine care is very important.
Needle and Sewing Thread Thickness
Unnecessarily high thread tensions can also have other causes. Are sewing thread and needle properly matched? If you are using a heavy duty thread with a tiny needle it might go wrong on the stitches. For an even stitch feed the thread tension must be increased, the sewing thread is unnecessarily stretched and generates ripples. The chart gives you a suitable advice for the right tuning.
The Quality of the Sewing Thread
There is nothing more frustrating than broken thread, skipped stitches and uneven tension. Choosing quality thread will greatly reduce the negative effects of stray fibers, allowing your machine to maintain even thread tension and eliminating weakness and breakage. Check the thread for knots and unevenness and make sure it will not get stuck in the eye of the needle or lead to an uneven stitch pattern. Most high quality threads are treated with a wax or silicone coating, which enables the thread to slide through fabric easily. Natural fiber threads, especially cotton and silk threads influence the sliding characteristics by their coloring. Check the quality of the yarn each time you use a new spool and adjust the thread tension if necessary. However, this is no longer necessary with the high quality polyester sewing threads. Thread tensions may also be product specific, i.e. the sewing thread may have unfavorable characteristics.
A typical example is the monofilament sewing threads, which have a high elongation and therefore must be sewn with a lot of thread tension. While sewing, the material starts to look a bit rippled Fine fabrics are often difficult to sew. A polyester thread with a lower elongation is a good choice. The stretching of the thread by the high thread tension causes skipped stitches and changes the characteristics of the thread. A high-quality sewing thread should be shrink-free. This can be checked very easily by ironing or even boiling 1 m sewing thread with steam. The shrinkage will be minimal.
When sewing the thread is stretched, this depends very much on the sewing thread. The higher the elasticity of the sewing thread, the higher the thread tension must be and the more the thread is stretched. If you separate the thread after sewing and measure the shrinkage again, you will notice that the sewing thread has shrunk by up to 5%. Therefore, it is important to make sure that the sewing thread has a low stretchability and the machine is set to the lowest possible thread tension. This will save your customers a lot of ironing work with easy-care clothing.
Instructions for the pattern construction of four different denim jackets.
You can find ready-made patterns for “sewing off right away” in our online shop.