Incorrect adjustment of the thread tension when working with an overlocker most often leads to the formation of loops on the back of the seam or, conversely, to pulling of the fabric. When you decide sew in one thread, failure to fine-tune the dials will cause immediate fabric breakage or skipped stitches, making further edge finishing impossible. Understanding the physics of thread passage through the mechanism allows you to avoid defects on expensive fabrics.
Specifics of working with knitwear requires the use of elastic seams, which only the correct machine configuration can provide. The misconception that it is enough to simply insert the thread into the needle, ignoring the path of the lower threads, leads to breakage of the needle bar or deformation loopers. For a high-quality result, you must strictly follow the sequence of actions described in the technical documentation for your model.
The main difficulty lies in balancing the pressure on the thread, since the standard settings for a four-thread seam are not applicable here. If you are planning sew in one thread for decorative stitching or hemming, you will have to completely rebuild the logic of the feed mechanism. Any deviation from the setting algorithm is fraught with the formation of a ball of thread under the foot.
Preparing the overlocker for working with one thread
Before starting the reconfiguration, you must turn off the power to the device and remove all four threads to prevent residue from getting tangled in the mechanism. Rotating the flywheel by hand will help clear the transport system of old material. The cleanliness of the mechanism is the key to ensuring that the new thread lies smoothly.
Depending on your overlocker model, you will need to change the needle position or use a special converter plate. Some modern cars Brother or Janome have a built-in lever to switch to single thread mode, whereas on industrial designs you need to physically remove the lower looper. Make sure the needle is inserted all the way into the needle clamp with the flat side facing the correct direction.
It is critically important to correctly thread the upper looper, since it is the one that will form the main part of the seam in this mode. The thread must be passed through the guide hooks under tension to prevent sagging. Check that the thread passes freely through all holes without snagging.
- 🧵 Completely remove old threads from all loopers and needles.
- 🔧 Install a new needle of the appropriate size for your fabric type.
- ⚙️ Lower the differential if an elastic seam is required, or raise it for stable fabrics.
- 🧹 Blow the mechanism with compressed air or clean the lint with a brush.
⚠️ Warning: Never try to adjust the thread tension while the machine is running. All disk adjustments are made only with the presser foot raised and the engine stopped.
After mechanical preparation, the condition of the knives should be checked. Dull knives can pull on the fabric, creating additional resistance that a single thread cannot compensate for. Sharpening or replacing knives often solves the problem of uneven blade advancement.
Setting Tension Controls for a Single Thread
The most important step is setting the values on the tension regulator disks. For single thread mode, standard indicators (usually 3-4) are not suitable, since the thread will either break or lie loosely. You need to find a balance where the knot is hidden within the thickness of the fabric.
Start by setting the value to "0" on all disks except the one through which the working thread passes. If you are using an upper looper, the corresponding disc is turned out to a value of 6-7, creating a strong tension. This causes the thread to wrap around the edge of the fabric, forming a tight overlock stitch.
If the thread constantly breaks when sewing, try lowering the tension by half a notch. Conversely, if the seam is loose and the loops are hanging, the tension should be increased. Thin synthetic threads require more delicate adjustments than thick cotton threads.
The table below shows approximate tension values for various types of fabrics when working with one thread. Remember that every machine is different and these numbers are just a starting point for calibration.
| Fabric type | Recommended Tension | Stitch length | Needle type |
|---|---|---|---|
| Thin knitwear | 5.5 - 6.0 | 2.0 - 2.5 mm | 75/11 Stretch |
| Heavy jersey | 6.0 - 6.5 | 2.5 - 3.0 mm | 90/14 Universal |
| Fleece/Footer | 6.5 - 7.0 | 3.0 - 3.5 mm | 90/14 Jersey |
| Silk/Chiffon | 4.5 - 5.0 | 1.5 - 2.0 mm | 70/10 Microtex |
Pay attention to the quality of the threads. Cheap threads with uneven thickness will constantly change tension during the sewing process, which will lead to marriage. Use high-quality polyester threads to achieve stable results.
Threading technique and thread path
The correct path of the thread through the guides is the foundation of a quality seam. An error at one of the refueling stages results in the machine not being able to sew in one thread without constant interruptions. Carefully follow the color markings on your machine's body.
First, the thread is threaded through the upper guide, then passes through the tension disk and only then enters the eye of the looper or needle. Using a threader makes this process much easier, especially when working with thin or fluffy threads.
☑️ Checklist for correct refueling
When working with cover machine The thread path may differ in the presence of additional compensators. Make sure that the thread is not stuck between the regulator discs. Sometimes it is necessary to pull the thread back and forth several times so that it “sits” in the grooves.
If you use decorative threads (metallic, floss), it is better to wind them on an additional bobbin and place them on top to reduce resistance. Direct use of such threads from the spool often results in them twisting and breaking.
⚠️ Attention: When threading, always hold the end of the thread in your hand and do not let go of it until you are sure that the thread is securely fixed in the mechanism. The free end may become entangled in the knives.
Choosing a needle and thread for a monofilament seam
For single filament mode, the choice of consumables is critical. Regular cotton threads may not provide sufficient strength and elasticity to the seam. The optimal choice is polyester threads, which have high tensile strength.
The needle must match the type of fabric. For knitwear, needles with a rounded tip are required (Stretch or Jersey), which push the fibers apart rather than pierce them. Using a sharp needle on jersey will create holes along the seam.
Needle and fabric compatibility chart
For thin knitwear (T-shirts), use needles No. 70-75. For thick knitwear (denim knitwear) - No. 90. For elastic fabrics with lycra, needles marked Stretch are required.
Thread diameter also affects settings. Thick decorative thread will require lowering the tension and possibly increasing the needle size. A thin thread, on the contrary, requires more precise tension adjustment so that it does not slip.
Don't skimp on needles. A dull or bent needle is the leading cause of skipped stitches and pulls in fabric. Replace the needle after every large project or when it shows the first signs of wear.
Elimination of typical seam defects
Even with proper setup, defects may occur that need to be diagnosed. If the seam turns out “shaggy” and the thread does not wrap around the edge of the fabric, then the tension is too weak. Increase the value on the regulator by 0.5-1 division.
If the fabric bunches up along the seam, it is a sign of too much tension or a stitch that is too short. Loosen the dials and increase the stitch length. Also check the presser foot pressure: for thin fabrics it should be reduced.
- 🧶 Bottom loops: loosen the tension on the top thread.
- 🧶 Thread break: check the quality of the thread, the condition of the needle and reduce the tension.
- 🧶 Skipping stitches: replace the needle, check the threading is correct.
- 🧶 The fabric is stretching: reduce the tension and increase the stitch length.
Helpful Hint: Before starting to work on a finished piece, always do a test run on the same piece of fabric. This will save you nerves and material.
A common problem is the fabric “bouncing” under the presser foot. In this case, using a special foot for knitwear or placing a strip of paper under the seam, which can then be easily removed, will help. Fabric stabilization improves stitch quality.
Features of working on a cover stitching machine
A coverstitch machine also allows you to sew with one thread, but the technology here is different from an overlocker. Here, one thread is usually used as the top decorative thread, while the bottom looper forms the chain. However, there are modes where only one needle and one looper are used.
When setting stitchers It is important to set the needle bar height correctly. If the needle drops too low, it may hit the looper, causing damage. Adjusting synchronization is a task for experienced users.
For decorative stitching, the one needle and two looper thread mode is often used, but you can also set it up to work with one thread to create a flatlock stitch effect. This requires fine-tuning the top thread tension to keep the chain underneath straight.
Main conclusion: The secret to a perfect one-thread seam is 80% correct tension setting and 20% quality of needle and thread. Don't be afraid to experiment with settings on scraps.
Remember that cover stitching machines are more sensitive to thread quality than regular overlockers. Use only special threads for cover stitches that have a smooth surface and minimal hairiness.
Frequently asked questions (FAQ)
Is it possible to sew with one thread on a regular sewing machine?
Yes, regular sewing machines sew with one thread (top thread), forming a seam with the bottom thread from the bobbin. However, the article is about an overlock stitch, which requires a specific looping mechanism, available only on overlockers and cover stitchers.
Why does the thread constantly break when sewing with one thread?
The main reasons: too much tension, a dull or incorrectly installed needle, poor thread quality or burrs on the thread guides. Check each of these points.
Which needle is best for stretch fabrics?
For stretchy fabrics (stretch, lycra, jersey), be sure to use marked needles Stretch or Jersey. They have a rounded tip that does not damage the fabric fibers, preventing the formation of holes and puffs.
Do I need to change knives when switching to one thread?
No, there is no need to change knives if they are sharp. However, when working in one thread, the load on the fabric changes, so make sure that the knives are not dull, otherwise they will pull the material, disrupting the uniformity of the seam.