Bunching threads, sometimes called “bird nesting,” is a problem encountered by all sewing machines at one time or another. There are some common, easy-to-address reasons for this. There are also other not-so-common reasons if the most common don’t seem to be the answer. I’ll try to address them all here.
The first question to answer is whether the thread is bunching on top of your fabric or beneath your fabric. Problems with bunching above the fabric often indicate a problem with the bobbin or other issues below, while bunching below the fabric often indicates a problem with the needle or other issues above.
Related: Why Fabric Keeps Getting Stuck In Your Sewing Machine
Why Your Sewing Machine Keeps Bunching Thread
1. Incorrect tension
This is the most common underlying problem when the thread is bunching either above or beneath the fabric. There will be a specific cause for the tension being out of whack. These specifics are covered over the next several reasons.
When the tension from above and below is in perfect balance, the threads entwine directly in line with the fabric. By using a different color in the bobbin and upper threads, you can balance your tension using a scrap of test fabric. You should not be able to see the bobbin thread color from the top of the fabric or the top thread color from the bottom side of the fabric.
When you change from one type or weight of fabric to another or change your thread’s weight, you should make appropriate adjustments to your tension. If you don’t, you run the risk of bunching or looping on one side of the fabric.
2. Improper threading
Improper threading affects thread tension. The tension may become either abnormally tight or loose, causing the bird’s nest effect on one side. If the bunching is on top, remove and rethread your bobbin. Then try sewing with a test piece.
If the bunching is under the fabric, rethread the upper part of your machine. Sometimes it’s a minor thing that can have a great effect, such as a missed guide or a spool cap that is missing or not secure.
3. Bobbin issues
Older machines and front-loading bobbin cases may have a small screw for adjusting bobbin tension. If you make adjustments to the bobbin tension, remember to tighten or loosen only in tiny increments, using test fabric to check adjustments.
You should also make sure the bobbin and bobbin case and any other removable pieces beneath the needle are inserted correctly and snuggly. Check for any damage to the bobbin case. Do not pry or try to make physical adjustments to the bobbin case beyond the screw adjustment.
4. Needle issues
A problem such as a dull needle or the wrong needle for the fabric can make the thread pull unevenly, causing bunching. Change the needle for each new project or partway through a large project if the tension becomes uneven.
It’s important to learn how to choose the correct needle for different fabric weights and layers. This will save you a lot of do-overs and headaches from many common sewing machine issues.
Again, if you’re not certain about your needle choice, try it with a test piece.
5. Improper machine maintenance
A sewing machine really is a somewhat delicate precision tool. As such, it can easily be thrown off by a lack of proper maintenance. Bird nesting is one issue that can result from neglecting your machine.
There are attachments available to fit most vacuum cleaner hoses to help remove lint from your machine. It is essential to remove all the pieces in the bobbin area periodically and clean out any lint or loose threads that may have accumulated there.
If you are working with fabric that is fuzzy or has a heavy nap, you may have to clean out the area more frequently to optimize your machine’s efficiency. Making stuffed animals or fleece blankets are a couple of examples to watch out for.
If you sew frequently, set a day each month when you will routinely clean and oil your machine. This will extend the life of this important sewing tool and keep it running at maximum proficiency.
6. Stitch length
Some fabrics cannot handle too fine a stitch length. The fabric may stick or be pulled downward, causing multiple stitches in one place. These stitches will bunch up and be difficult to remove. Adjust the length to a longer setting and try again with a test piece.
7. Thread tails too short
Always allow at least 3 inches to extend behind the cloth as you start to sew. This will keep the threads from being sucked under the fabric and getting caught in the bobbin area. This can cause bunching and jamming on either side of the fabric.
8. Using a stabilizer
Wash away or heat-away fabric stabilizers, or even fusible interfacing, can help keep some fabrics flat and controllable during sewing. Still, they have the potential of causing a build-up on the needle. Eventually, tension can become affected, causing thread bunching.
Follow directions carefully when using these types of products. Replace the needle if it becomes compromised.
9. Fabric is unsuitable for the machine
Some sewing machines are simply not intended to sew heavy materials such as leather or pleather. Some may not be able to handle too many layers of fabric. Trying to force a machine to operate beyond its manufactured parameters can cause thread bunching as the tension is unable to accommodate the thickness.
Sewing beyond your machine’s capacity can cause permanent damage to machine parts as well. If you are facing this issue, it may be time to invest in a more heavy-duty machine to continue your creative efforts.
10. Simple mistakes
A few other simple mistakes can cause the thread to bunch up either above or below the fabric. Here are a few to look for:
- The feed dogs are down
- The presser foot was not lowered
- The take-up lever was not at its topmost position before starting to sew
