Why does my sewing machine make loops?

Nothing is more frustrating than seeing your efforts undone by sewing machine loops that coil under the fabric or rebel on the surface. These imperfections, often caused by a conflict between upper thread and bobbin tension, distracted threading, or a dull needle, turn the joy of creating into an obstacle course. If you’re wondering why my sewing machine makes loops, know that the answer is often hidden in these precise settings. 

Learn to decode every symptom, adjust settings precisely on a fabric scrap, and regain full control of your seams.

Why does your sewing machine make loops?

Are you just starting to sew but notice unsightly loops under the fabric? Don’t worry, this problem is common and even affects experienced sewists. These loops indicate an imbalance between the upper thread and the bobbin thread, often due to incorrect tension, improper threading, or lack of maintenance. With a few simple adjustments, you’ll get clean seams in no time.

Loops aren’t a mystery. In fact, they signal a conflict between two essential elements. If the upper thread is too loose, it forms loops. If the bobbin tension is off, the lower thread dominates and creates visible bumps. Even a dirty bobbin case or damaged thread can cause this disorder. 

The perfect stitch is recognized by a perfect balance with both threads crossing in the middle of the fabric without showing on either side. We’ll help you identify the exact cause and fix it stress-free.

First, we’ll explore how to analyze the loops to understand their origin. Then, you’ll learn how to check the upper thread and bobbin tension, redo the threading step by step, and clean the machine’s critical areas. 

Simple tips, like observing the direction of the loops (under the fabric or on top), will help you accurately diagnose the issue. Say goodbye to uneven seams and turn your mistakes into successes!

Diagnose the problem: are the loops above or below the fabric?

Loops on your seams reveal a tension imbalance in the machine. Start by checking whether these loops appear under or on top of the fabric. This analysis directly targets the source of the problem.

Loops under the fabric indicate an upper thread that is too loose. This results from insufficient tension or incorrect threading. A common oversight is when the thread is not passed through the needle bar thread guide. Check each threading step to identify the error.

Conversely, loops on the top of the fabric indicate a poorly tensioned bobbin thread. The upper thread tension may be too high, or the bobbin tension too low. A common case: a bobbin thread wound by hand instead of the winder, which creates uneven tension.

To confirm your adjustments, always test on a scrap of fabric identical to your project. This isolates the parameters causing the problem, as fabric thickness affects the ideal tension.

Regular cleaning of the tension discs and bobbin case prevents uneven tensions. If in doubt, professional servicing remains a reliable solution.

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The number one cause of loops: incorrect tension adjustment

When a sewing machine produces loops under the fabric, the problem often comes from an imbalance between the tension of the upper thread and the bobbin thread. The perfect stitch interlocks within the layers, invisible on the front or back. An improper setting disrupts this balance and creates unsightly loops.

How to adjust the upper thread tension?

The tension dial, usually numbered, allows you to tighten (higher number) or loosen (lower number) the upper thread. Start with the standard setting (often 4 or 5). For thick fabrics (canvas), a slightly higher tension (6-7) may be necessary. 

For fine fabrics (like silk), favor 3-4. If loops appear under the fabric, gradually increase tension (5 → 6) and test after each change.

The yo-yo test to check the bobbin

Adjusting bobbin thread tension is less common. For removable cases, do the yo-yo test: hang the bobbin by its thread and give it a shake. If it drops slightly, the tension is good. 

If it drops, tighten the screw (clockwise). If it stays still, loosen it (counterclockwise). For horizontal bobbins, check their positioning: a poorly inserted case causes loops.

Here’s how to proceed: 

1. Prepare a sample with the project’s fabric and threads.
2. Set the upper tension to 4 or 5 (standard value).
3. Sew a straight line a few centimeters long.
4. Check both sides: spot loops on top or bottom.
5. Adjust the tension: increase it (5 → 6) if loops are under the fabric.
6. Lower it (5 → 3) if loops appear on the top.
7. Repeat until you get an invisible and balanced stitch.

When and how to adjust tension?

Test on a sample, especially for unusual fabrics. Electronic machines sometimes have an “auto” mode, but manual adjustment is sometimes necessary. Clean the tension discs and bobbin case regularly, as dust interferes with thread flow. 

Check the needle, because if it’s dull or inserted incorrectly, it can disrupt tension. When in doubt, rethread the machine before adjusting the bobbin, as incorrect threading is often the main cause of loops.

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Beyond tension: other common causes of loops

You’ve checked the thread tension, yet loops still appear? Other factors deserve your attention. Discover the common mistakes that turn your project into a knotty mess.

Incorrect upper thread threading

Most threading problems come from a forgotten step: the presser foot must be raised during threading. This releases the tension discs, allowing the thread to position correctly. Forgetting this step is like trying to pass a necklace through a ring without opening the clasp!

Always check that the thread passes through all the guides, including the thread take-up lever. Missing a guide creates uneven friction that causes loops. Need a reference? Check the threading diagram in your machine’s manual.

Problems related to the bobbin

A poorly inserted bobbin breaks the rules of sewing. The thread must wind in the correct direction (usually counterclockwise for horizontal bobbins). A poorly wound bobbin, with loose or misaligned thread, releases its thread chaotically.

Inspect your bobbin, as scratches, deformation, or poorly oriented thread are enough to disrupt the stitch. If the bobbin case is damaged, even slightly, replace it. An ill-fitting bobbin case acts like a bad dance partner who always ends up tripping the step.

The mismatched thread and needle pair

A thick thread with a fine needle causes excessive tension. Conversely, a fine thread in a large needle moves without precise guidance. The needle size must match the thread diameter, like a lock to its key.

A dull or bent needle worsens the problem because it forces the thread to twist or break. Change the needle as soon as you feel any snagging during stitching.

Ask yourself these questions to see if the thread and needle pair is working well:

• Is the presser foot fully raised when threading?
• Does the upper thread pass through ALL the guides, including the take-up lever?
• Is the bobbin inserted in the correct direction of rotation?
• Is the bobbin thread wound smoothly and evenly?
• Is the needle suitable for both the fabric AND the thread? Is it in good condition?

By adjusting these settings, you eliminate 90% of mysterious loops. Once these steps are confirmed, even the most challenging fabrics will hold no secrets for you.

The influence of the fabric and the specifics of your machine

Are you wondering why your sewing machine is making loops even though you’re following all the steps correctly? Often, the answer lies in the choice of fabric and the settings suited to your machine. Between the influence of the presser foot, the sewing technique used, and the differences between mechanical and electronic models, every detail can turn your sewing experience into a success or a frustration.

The impact of fabric type

The type of fabric directly affects the appearance of loops. Fine or slippery fabrics like silk require a microtex needle and reduced tension to avoid irregular stitches. Choose a fine polyester thread (50/2) for these delicate fabrics, as its flexibility reduces friction.

For thick fabrics (denim, faux leather), use a strong needle (90/14 or 100/16) and a thicker thread (60/2 or 40/2) and slightly increase the upper thread tension (around 4.5-5 on a scale of 1 to 9) to compensate for thickness. A presser foot for thick fabrics helps feed the fabric without distortion.

Stretch fabrics (jersey) stretch during sewing. Prefer a stretch or ballpoint needle (70/10 or 90/14) and an elastic stitch (light zigzag or overlock) to prevent the stitch from breaking. Reduce the presser foot pressure to avoid crushing the fabric, especially on models with manual adjustment.

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The role of the presser foot and technique

The standard presser foot is not always optimal. Dual-feed feet (like the walking foot) are better suited for thick fabrics, while Teflon feet glide over synthetic materials. Adjustable opening feet adapt to changing thicknesses, such as topstitching.

Avoid forcing the fabric and let the machine control the feed, as rough handling disrupts thread tension. Stabilize slippery fabrics with double-sided tape or a layer of tulle before sewing. For thick fabrics, slightly lift the presser foot edge to ease the passage of layers.

Differences between mechanical and electronic machines

Mechanical machines require preliminary tests on a fabric scrap. Repeated loops often indicate incomplete threading or dirt buildup. Regularly clean the bobbin case with a soft-bristle brush to prevent lint deposits.

Electronic models sometimes have automatic tension sensors. In case of loops, check that the optical sensor is not blocked by debris. Some display error codes (e.g., "thread error") indicating a threading problem. Use the "automatic cleaning" option if available, following the manual's instructions.

Whatever the machine type, regular cleaning of the thread guides and bobbin case is essential. Lint buildup systematically disrupts thread tension. Release the upper thread tension at the end of sewing to avoid thread backlashes.

Preventing loops: good maintenance habits

Loops under the fabric are often avoidable. A well-maintained machine reduces these issues. Did you know lint or a worn needle can cause problems? Here are simple steps to avoid these annoyances:

Regular cleaning is essential

Thread residues and lint build up in the bobbin and under the needle plate. After each project, dust these areas with the provided brush and don’t forget the feed dogs, as they affect stitch quality.

Needle replacement

A dull needle affects tension. Change it every 8 to 10 hours of sewing. Check its proper positioning: it must be straight and securely in place. A new needle prevents slipping on all fabrics.

Lubrication

Oil only the moving metal parts, like the needle shaft, and consult your manual for exact points. Use 1 to 2 drops of specific oil, avoiding excess. Light lubrication improves the lower thread’s smoothness.

Your maintenance routine for worry-free sewing:

• Dust off the bobbin after each project.
• Change the needle before a new garment or after 8 hours of use.
• Use high-quality threads without excess lint.
• Test on a sample before the final sewing.
• Store the machine away from dust with its cover.

By following these steps, you will reduce the risk of loops and extend your machine's life. Adopt these simple habits for clean stitches every time you sew.

Sewing machine loops are a common problem, but easy to fix with the right steps. By adjusting the tension, checking the threading and bobbin, and matching your equipment to the fabric, you'll get clean stitching back. A well-maintained machine and preliminary tests ensure perfect results.