How to Adjust Bobbin Tension for Smooth, Balanced Stitches | YLI

Introduction: Why Bobbin Tension Matters

Every quilter understands the struggle: hours into an exciting project, feeling the rhythm of your stitches, when suddenly you examine the back of your quilt and the threads resemble a chaotic threadstorm! Loops, puckers, broken threads, and skipped stitches are classic signs that your sewing machine's tension may be unbalanced. While we recommend starting with adjusting the top tension (please read our educational article on balanced tension if you haven't yet), which often resolves these issues, there are times when the bobbin tension is the culprit and the reason for uneven thread tension.

This educational article focuses on bobbin tension for both home sewing machines and longarm machines. Understanding the role of bobbin tension in achieving balanced, high-quality stitches will serve you well. The content in this article is written based on the assumption that you have already adjusted your top tension as necessary and continue to experience tension issues that lead you to believe the bobbin tension needs to be adjusted. The good news is that changing your bobbin tension isn't as intimidating as you might think. With a few simple steps and a little practice, you can quickly rectify any tension issue and keep your machine running smoothly, with perfectly balanced stitches.

Minor, quarter-turn adjustments to the bobbin case's tension screw are all that's needed to increase or decrease the tension on the bobbin thread.

Tension 101 – Start With the Basics

The top tension of your machine is mainly influenced by the tension discs, which apply pressure to the top thread through a spring mechanism or electromagnets as the thread passes through. The tension control apparatus, a wheel, rotary dial, or digital touch screen, allows you to adjust the tension by setting a number between 0 and 9. A higher number indicates tighter tension, with a lower number indicating looser tension.

tension control on a computerized sewing machine

Tension settings are displayed on a computerized sewing machine.

A combination of factors affects top tension management on longarm machines. These include the primary tensioner, which consists of tension discs regulated by a spring and screw mechanism, and a tension guide or rod, typically a small metal bar with three holes through which the thread loops. Some machines also feature an intermittent tensioner or a thread sensor guide, as well as an additional thread guide or rod near the cone holder.

A good rule of thumb is that the more contact the top thread has with the machine, the greater the tension placed on the thread. To loosen the top tension on a longarm machine, adjust the spring tension on the primary tensioner and reduce the number of contact points the thread has with the machine. You can achieve this by threading the top thread through only one of the three holes in the tension guide, bypassing the intermittent tensioner, or skipping the first thread guide, among other methods.

The three-hole tension guide on a longarm machine with QuiltMaker thread.

close up image of a longarm machine tension assembly

A longarm machine's main tension assembly. The spring applies pressure to the discs, which controls tension on the thread.

Understanding Bobbin Tension

Tension control on a bobbin thread is very different than the top thread. There are no tension discs or electromagnets on the bobbin case. Instead, bobbin cases have a tiny metal spring that the bobbin thread passes through during the threading process. There is a small screw on the spring that, when tightened, shrinks the gap between the spring and the case, thus adding pressure to the thread. When the screw is loosened, it reduces the pressure on the spring, thereby decreasing the tension on the thread.

Think of the top thread and bobbin thread as dance partners in the "Waltz of the Stitches." They have to work together, each pulling with equal force, so the stitch locks neatly in the middle of your quilt sandwich. If one partner pulls harder than the other, the choreography will struggle, and the entire performance will stumble.

Examples of Unbalanced Bobbin Tension include:

Hallmarks of too-tight bobbin tension include: The top thread is being pulled harshly to the underside of the quilt, resulting in the top thread forming loops (called looping), or a bird's nest (which is the tangling and buildup of thread), or repeatedly broken threads.
Hallmarks of too-loose bobbin tension include: Bobbin thread peeking through the top fabric. If you see what looks like dots or even whole stitches of your bobbin thread on the top of your quilt sandwich, the top bobbin tension is too loose (your top tension could be too tight), resulting in the top thread pulling the bobbin thread to the surface.

The Role of the Bobbin Case

The bobbin case is the part of your sewing machine that holds the bobbin securely in place under the needle plate. As you stitch, the case keeps the bobbin steady while allowing the thread to feed out smoothly so the machine can form stitches. Each time the needle comes down, the machine's hook catches the bobbin thread and joins it with the top thread to create a strong, balanced stitch.

Beyond simply holding the bobbin, the case also controls the tension of the bobbin thread. A small spring inside the case adds just the right amount of resistance, allowing the thread to flow evenly. This balance is what keeps your stitches looking neat on both sides of your quilt sandwich. When the bobbin case is working correctly, your seams lie flat, your stitches are even, and you can quilt with confidence knowing your machine is helping you achieve a polished finish.

Depending on the machine, the bobbin case will be either:

Drop-in bobbin case (inset type)
Front-load/side-load bobbin case (removable type)

close up image of a drop-in bobbin case for class 15 bobbins

A standard drop-in bobbin case for a sewing machine that uses Class 15 bobbins.

a close-up image of a M-style bobbin case

A metal M-style bobbin case with the tension adjustment screw visible.

How to Test and Adjust Bobbin Tension

Begin by cleaning the bobbin area. Use a small brush to remove lint, dust, and any loose threads. Cleaning helps prevent tension issues before they start.

Next, mark your baseline. Using a fine-point permanent marker, place a small dot next to the screw on your bobbin case, where the line of the screw is facing. Doing this gives you a clear reference point in case you need to return to the original setting. Refer to the image of the metal bobbin case above to locate the small black dot as an example.

To test your current bobbin tension, thread your machine as usual with the same top and bobbin thread you plan to use. Stitch a straight line on a fabric scrap similar to your project. Check both sides of the fabric:

Balanced tension produces even stitches on the top and bottom.
Loops on the underside suggest bobbin tension is too tight or the top tension is too loose.
The bobbin thread showing on the top means the bobbin tension may be too loose or the top tension too tight.

For front-load or side-load bobbin cases, locate the small tension screw on the case. Turn the screw clockwise to increase tension or counterclockwise to decrease it. Adjust in small increments, no more than one quarter-turn at a time. Test after each adjustment.

For drop-in bobbins, remove the needle plate, then remove the bobbin cover and bobbin case. Locate the small screw on the metal leaf spring. Make the same quarter-turn adjustments as you would on a front-load bobbin case.

Small changes go a long way. Always test on scrap fabric before returning to your project. Proper bobbin tension helps create smooth, consistent stitches, reducing frustration during quilting.

Troubleshooting Bobbin Tension Issues

We've created this handy reference table that shows symptoms, likely cause, and a quick fix to address bobbin tension imbalance. This table is intended for reference after the following steps have been completed: rethreading the top thread, checking the needle for burrs or wear, replacing the needle if necessary, and adjusting the top tension. Once these adjustments have been made and tension issues persist, it's time to adjust the bobbin tension.

Symptom	Likely Cause	Quick Fix
Loops or bird's nests on the underside	Bobbin tension too tight or top tension too loose	Tighten the bobbin tension screw 1/4 turn clockwise; rethread the top thread
Bobbin thread is visible on top	Bobbin tension is too loose	Tighten the bobbin tension screw 1/4 turn clockwise
The top thread is pulled and piling underneath	Bobbin tension is too tight	Loosen bobbin tension screw 1/4 turn counterclockwise
The top thread breaks frequently	Tension too tight or a bad/incorrect needle	Loosen bobbin tension slightly, replace the needle
Puckered fabric	Overall, tension is too tight	Reduce both the top and bobbin tension slightly
Railroad tracks	The top tension is too tight relative to the bobbin	Loosen the top tension more than you think you need to, or tighten the bobbin tension screw by a 1/4 turn
Eyelashes	The top tension is too loose or the thread isn't in the take-up level/misthreaded	Tighten the top tension or loosen the bobbin tension screw by 1/4 turn counterclockwise, rethread both top thread and bobbin

How Thread Type and Weight Affect Bobbin Tension

Not all threads perform or behave the same way in your machine. For instance, if you are quilting or sewing with an ultra-fine Invisible Thread (monofilament) and then switch to a heavier 40 wt. cotton thread, such as Majestic, your machine doesn’t automatically adjust its bobbin tension.

You Are a Bobbin Tension Pro

Mastering bobbin tension is less about mystery and more about method. The process is the same when you're quilting on a home machine or longarm; balanced tension means stronger seams, smoother stitches, and quilts you'll be proud to show off.

The more you work with your tension settings and understand how thread type and weight play a role, the more confident you'll become. So grab your scrap fabric, make those tiny adjustments, and quilt on with precision.

Best Practices for Maintaining Balanced Tension

Always clean your bobbin case before making any adjustments.
Make incremental changes — ¼ turn at a time.
Keep a small notebook or digital note for "go-to" settings for different threads.
Test before starting every new project, especially when changing fabrics or thread weights.
Don't fear adjustments. With practice, you'll know exactly how to get perfect stitches.

About YLI's 40 wt. Majestic Quilting Thread

For machine quilting, our 40 wt. Majestic thread is genuinely exceptional. Made from 100% Egyptian-grown extra-long staple cotton, this thread is available in forty-five variegated colors and five solid colors. Bold and ready to enhance any quilt with eye-catching motifs, filigree, feathers, or edge-to-edge designs. Majestic is one of our premium cotton quilting threads, available in 2,000-yard cones and 600-yard spools.

Get inspired by Majestic colors

cones and spools of majestic cotton quilting thread

Frequently Asked Questions

What thread do you recommend for piecing quilt blocks?

For cotton lovers, Dream Seam is an excellent choice. This 50 wt. thread is made from 100% Egyptian-grown extra-long staple cotton, which means it's smoother, stronger, and produces far less lint than standard cotton threads. It's also mercerized for a soft sheen and gassed to remove fuzz, keeping your seams crisp and your machine cleaner.

If you prefer polyester, Perfection is a great alternative. This 50 wt. gently-textured polyester thread is completely lint-free, strong without being stiff, and blends so well into fabric that stitches nearly disappear.

For best results, pair either thread with a Topstitch #80/12 needle. The larger eye and deep groove of the Topstitch needle protect the thread, reducing skipped stitches, shredding, and breakage.

How important is it for the bobbin and top thread to match?

On a scale of zero to ten, this is a zero. Of course, there is no problem using different or matching threads on the top and in the bobbin. Here are things to consider:

The top thread is usually selected to enhance the quilt. Ultra-fine threads (monofilament/invisible threads, 100 wt.) are nearly invisible and don't add design flair to the quilt. Fine threads (60 wt. and 50 wt.) blend effortlessly into the fabric and are less noticeable, allowing the stitching pattern to be the focus. Medium (40 wt.), heavier (30 wt.), and variegated threads are designed to be visible and add personality to your quilt top. For very busy prints or a quilt top with many colors, an invisible thread (monofilament) is a quilter's favorite because the thread doesn't stand out.

There is no problem mixing thread types, such as using cotton on top and poly in the bobbin, or vice versa. There is also no problem mixing thread weights, for example, 40 wt. on top and 60 wt. in the bobbin. Prewound bobbins are very popular, and most prewounds are 50 wt. or 60 wt. threads. No problem using one of these prewounds with a thread of a different weight as the top. As a bonus, commercially wound prewound bobbins have more thread than self-wound bobbins.

How can I adjust my tension so the top thread and bobbin thread are perfectly even or balanced?

To achieve balanced tension, start by making minor adjustments to your top tension. On a home sewing machine, you'll either adjust the tension dial to a lower setting or, if you have a computerized machine, lower the tension through the touchscreen to loosen the top tension. To increase tension, move the dial to a higher number. When you feel like the top tension is right, perform a test stitch on scrap fabric using the same thread and needle as you'll use on your quilt.

If the top thread is visible or looping on the underside of the scrap fabric, increase the top tension. If your bobbin thread is being pulled up to the top of the scrap fabric, loosen the top tension. Make any adjustment in small increments, with an exception when quilting with metallic, monofilament (invisible), or other delicate or very-fine threads. When using these threads, start by setting your top tension to 1.0 and then increase slowly as necessary.

Ensure that the needle size matches the thread weight as well. If the needle is too small, it will add friction with each stitch and could cause fraying and broken threads.

My friend was told her that her new computerized sewing machine could only use certain thread types and weights. Is this true?

It's a common question, and the short answer is no. While some dealers or manuals may recommend specific threads, most home and longarm machines can handle a wide variety of thread types and weights, including cotton, polyester, nylon, and silk.

The key is to pair your thread with the correct needle size and set the proper tension. A high-quality 50 wt. cotton, like Dream Seam, or a smooth 60 wt. polyester, like Precision, will run beautifully in a well-maintained machine (you could even use cotton on top and polyester in the bobbin at the same time). With the right combination of proper needle, tension, and thread, your machine is far more versatile than it may seem. So, keep using the threads you love and enjoy the creative freedom they offer.

Can I use prewound bobbins in my machine? A friend told me it would void my warranty.

This is a common myth, but it is not true. High-quality prewound bobbins are safe to use in all sewing and longarm machines.

We use prewound bobbins every day in our sewing classroom (with over a dozen different machines) and in the longarm machines we use for quilting services in our store. They are reliable and efficient.

Here's why we love them:

They save time by eliminating the need to wind your bobbins.
They're precision-wound with professional-grade equipment for a tighter, more uniform bobbin.
They hold up to 70% more thread than self-wound bobbins, so you stitch longer with fewer interruptions.
YLI's prewound bobbins use the same high-quality thread on our spools and cones. We offer them in both Dream Seam and Precision, and we recommend them to any quilter who values smooth stitching, consistent tension, and maximum convenience (and who doesn't?).