Sewing machine thread tension is something we generally don’t think about. That is until we notice a tangled mess of thread and/or threads just lying on the surface of the fabric. Don’t despair! Dry your tears! Fixable and with patience you and your best friend the seam ripper can save the fabric!
a perfect stitch
A perfect stitch happens when the top thread and bobbin thread meet in the middle. They will form even stitches. The top thread will not show on the bottom and no bobbin thread shows on top. Thread tension for perfect stitches is the goal for sewing.
If tension were the only thing that determined perfect stitches and you only used 50 or 60 weight thread no matter what you are making, you could skip this lesson. Machines come from the factory with preset tension for those thread weights from identical fiber. However, it is not that difficult to change tension to accommodate other threads and get perfect stitches. So, you just might want to keep reading!
Tension is only one part of making this happen. Needles need to be the correct size for the thread and type for the fabric you are using. Having the thread that is the same size and weight in both the bobbin and needle is helpful for this lesson. Beware, they don’t have to be once you know how to work with different threads. That will be covered in the More About…Section.
your sewing machine thread tension
Test your sewing machine thread tension to determine if it is giving you perfect stitches. First, use the white or black thread in the bobbin and the other for upper threading. Checking your threading and bobbin placement before stitching eliminates two factors that could affect the stitches made.
Next, double your fabric piece so the thickness is two layers. Place it under the foot at the feed dogs, lower the foot, and sew a line of stitches a couple inches long using a mid-long length stitch. Leave the tension where it is set. Cut the thread and remove the fabric sample from the machine. Do you see the bottom thread on top or vice-versa? Are your stitches well-formed and even? Now open the two layers of fabric. You may need to pull the pieces apart a little with equal force on each side to enable you to see the stitches. What you are hoping to see are the top and bottom thread meeting exactly at the seam. Gentle tugging exposes the interlocked stitch you see equal distance from the fabric.
top thread tension adjusting
Most tension issues can be corrected by adjusting the top thread tension only. If you see the upper thread on the bottom, your tension is too loose. Tighten the tension by no more than one number higher before testing again until you have a perfect stitch. If the bobbin thread is seen on top fabric, the top tension is too tight. Loosen the tension one number at a time to test until you reach the perfect setting. The higher numbers mean more tension, the lower numbers loosen the tension of the top thread.
testing the bobbin thread tension
Before testing the bobbin thread tension in the case, look closely at the bobbin case. You will notice either one or two screw heads. “Don’t touch! Look with your eyes, not your fingers!” Do you have any idea how often I said that when my five “touch everything” kids were growing up?
The larger of the small screws adjusts the bobbin tension by the pressure it exerts on the metal and in turn, the thread. That little screw does a big job with just the smallest amount of movement. Rarely will you have occasion to adjust the bobbin case. When you do, remember the larger of the two screws is the one you will be adjusting.
Clean the bobbin case if needed before correctly inserting the well wound bobbin. Place the bobbin in the case in the palm of your non-dominated hand. Then, lift the unit by extending the thread a couple inches from your palm. If you cannot lift it without the bobbin case sliding downward, the tension is too loose. Gently bounce the thread. The bobbin case should drop slowly. If it does not drop at all, the tension is too tight.
adjusting bobbin tension
Adjusting the bobbin tension is not particularly difficult and is the same idea as the upper tension adjustments. The biggest, or should I say smallest, difference is lower tension is adjusted with a short screw that can fall out and disappear because it is so small! The tips will help you.
Mark the case at the screw notch on one end, then put a dot by the notch in the screw. This will tell you where it was when adjusting began. A washable marker is perfect for this. Next, place the bobbin case inside a large transparent plastic bag for your hand to reach inside with a small screwdriver. * Most sewing machines come with appropriate size tools you may need.
If the bobbin thread is seen on the upper thread side of the fabric and loosening the upper tension has not fixed it, you will turn the screw to the right. Think of the screw as a clock face with the marked notch pointing to 12 o’clock. Do not turn the screw more than to the 1 o’clock on the clock face. If the bobbin thread is pulling the top thread to the bottom, loosen the tension starting with a left turn of the screw to 11 o’clock. Re-insert the bobbin, stitch a test line of stitching. If further adjustment is needed follow the same steps, making one-hour increments of the notch each time. Remember to use the bag!
drop-in bobbins
Drop-in bobbins and if the bobbin tension can be adjusted is dependent on the brand and model of machine you have. Refer to your manual or ask the sewing machine retailer or repair person to advise you. There are many articles if you Google, and You Tube has help as well. Knowing I am not leaving you without resources, I don’t feel bad admitting I truly don’t know how to adjust bobbin tension on all makes of sewing machines. My drop-in machine manual does not address bobbin tension at all.
resolving tension issues
This was written with intent to help in resolving tension issues. Did you find it helpful or a bit scary? Adjusting tension is nothing to fear if you don’t get overzealous. All adjustments are in small increments. This goes for upper and lower tensions.
Experimentation: Sewing machine thread tension
Ready to do a bit of experimentation? We will stick with the upper thread tension for this hands-on fun. You should know where the tension control is on your machine. If not, check your manual. If your memory is easily distracted, jot down the setting where you will be starting from. I am presuming it is the tension that gave you your perfect stitch. If not, the following steps may help you reach perfection!
Step One: Turn the tension dial to the next highest number and take a few test stitches. What you may see is bobbin thread at each end of a stitch. Your upper thread has more pull than the lower stitch. Now you truly have a choice if to adjust the upper tension or the bobbin tension. Either way will eventually get you to an even stitch. Your threads are the same weight and fiber content, so it makes sense to adjust the upper tension.
Step Two: Let’s pretend your memory was not on duty when you moved the dial, so you are going to guess you should turn toward the smaller number TWO places. Stitch another line of test stitching. How does the top stitch look? How about the stitch on the reverse side? Top thread noticeable? That tells you what? If you said the bottom thread is too strong now and the top thread therefore is not pulling as hard, you are correct.
Step Three: Finally, put the top tension at the exact spot where it was when you started. Your test line of stitches should now be once again perfect! If not, check that the top thread did not slide out of the tension discs when you were changing them. Fix it if necessary and do another test. Better results?
Wrapping Up
I do hope you enjoyed playing with the tension. Hopefully, no one has instructed you never to change it. I wonder if they ever questioned why it was there. It was common to be warned not to touch it back when I was young and sewing. Perhaps it was because all the different weight threads and specialty threads were not readily available, if at all. Therefore, there apparently was never a need to adjust the tension. When you use heavier threads, metallic threads, or silk threads, you may find the best stitches require tension adjustments.
I am not a representative of Superior Threads although most of my threads are from them as well as what I have learned about thread and needles. If you want to learn more about thread and tension, check out their workshop notes at www.superiorthreads.com.
The previous post on Learn from Stitcher can be found by clicking on Threading a Sewing Machine.
*For those wondering why I suggested placing the bobbin case in a plastic bag, the stem on that tiny screw is so short, it is possible for it to fall out of the hole. The needle in the haystack is nothing compared to this little screw on the loose!