I’ve been teaching machine quilting classes for more than two decades now, and I’d have to say that the NUMBER ONE issue (problem) that machine quilters deal with is thread tension. So, I’ve decided to attack this behemoth issue, and really get down in the weeds about it. I hope that after this “in-depth” discussion on the subject, it will become vastly more clear to you how the threads in your machine work, and you will have the tools (knowledge) to solve your own thread tension problems in the future.
Way back, eons ago, when I started machine quilting, it was VERY common that when a quilter showed a quilt to someone and he/she realized it had been machine quilted rather than hand quilted it, they would immediately flip the quilt over to look at the back. Why, you may wonder. Well, it was to critique the bobbin thread tension. Apparently getting good thread tension on the back of your quilt (bobbin thread) was the criteria for being a good machine quilter.
All these years later, we still have thread tension issues (you’d think we would have solved this problem, just like I think they should have solved the lack of cell phone service in so many areas!). But solving thread tension problems varies from situation to situation. So let’s discuss some of those factors.
First of all, let’s define the term “Thread tension”. Without Googling this term or looking it up elsewhere, I’m simply going to explain is as I understand it. Basically, it is the balance (or struggle) between the top thread and the bobbin thread. As you know, when we sew on our sewing machines, the top thread and bobbin thread meet in the bobbin case and the top thread loops around the bobbin thread and pulls it up to the fabric, forming a stitch. Ideally, we want the stitches on the top of our fabric (or quilts) to look exactly the same as the stitches on the bottom of the fabric (or quilt). For quilting, to achieve this, we’d like the top and bobbin thread to meet in the middle of the batting. We want our stitches to be as symmetrical as possible.
Easier said than done though, right? So let’s discuss some of the factors that can make “balanced thread tension” harder to achieve.
1) Fabrics: I have found that stiff fabrics, such as batiks and painted fabrics make getting balanced thread tension very difficult. This is because the thread doesn’t sink softly into the fabric, but rather it lies on top of the fabric because the fabric is stiff.
2) Threads: Heavy threads can be harder to deal with in regards to tension because they are usually stiff. For instance, let’s think about metallic threads. They’re stiff, right? And if you’re using one of them in the top of your machine, your bobbin thread has to work very hard to pull that stiff thread down through the needle hole in the quilt to meet it in the middle of your quilt. So, for achieving nice thread tension, it’s always best to use a soft, supple thread if possible.
3) Needles: To achieve the best thread tension you can, it’s really important to match the needle size to the thread size. In the old days you use to have to figure this out by trial and error. But luckily now there are some thread companies (Superior Threads, for instance) that actually make needle recommendations right on the spool of thread. I think this is very helpful.
4) Batting: First of all, the batting thickness will have a big impact on how your thread tension balance is affected. For example, thin batts are sometimes harder to achieve good tension with because there’s just not much space in the layer of batting for the top and bobbin threads to meet. Stiff batts can also pose difficulties in getting good tension, again because the threads cannot easily “sink” into the layer of batting. With hundreds of types of batting on the market today, you’ll just have to experiment and see which ones you like best, but my three favorites are: Hobbs Tuscany Wool (for competition quilts), Hobbs 80/20 for cozy quilts, and Quilter’s Dream Cotton (also for cozy quilts).
Now let’s discuss how to adjust your thread tension to perfect your results (and if you need more information than this blog presents, I do discuss thread tension in my iquilt class, Successful Machine Quilting, Basic and Beyond).
TOP THREAD TENSION: First of all, let me explain what that even means! Basically, your top thread tension determines how much strength, power, etc. that you’re giving to the top thread to pull up the bobbin thread. So if you envision a “tug of war” between the top and bobbin thread, if you increase the top thread tension from its default setting of around 5, to an 8 or 9, you’re really giving the top thread a lot more power over the bobbin thread. But, depending upon the type of thread you have in the bobbin, sometimes this may be necessary.
Your top thread tension can be adjusted in one of several ways. On older sewing machines, there was a dial with numbers on it that was on top of the thread tensioner that you threaded your thread through (see photo). Usually the numbering went from 0-9, and somewhere around 5 was a good, intermediate tension. If you went to a number lower than 5, that would loosen the tension. A number higher than 5 would increase the tension.
When those types of tension knobs became a little outdated, the dial type on the top of the machine became popular. This is what my BERNINA 440 QE has, and it’s still my favorite type of tension adjustment because it’s EASY! For these dial types, they also go from 0-9, with a red line on the 5 to show the “default” tension. Then came the more elaborate, computerized machines, in which you had to go into your screen or menu, click on the thread tension icon, open up that screen, and then adjust your tension either up or down (too much hoopla for me!).
BOBBIN THREAD TENSION: Many of my students have never adjusted their bobbin case screw in order to adjust their bobbin thread tension. For some that’s a “voo-doo” subject. They’ve been told by their sewing machine dealer not to mess with the bobbin case because it’s preset at factory standard. Bah! I would never have been able to win hundreds of national awards for quilting if I hadn’t been able to adjust my bobbin case tension. If you have a bobbin case that can be removed from the under side of your sewing machine, then it will have a screw that can be used to adjust the bobbin thread tension. This screw is small, and you’ll need a very small screwdriver. To increase the bobbin thread tension (therefore making it pull down the top thread more), you turn that screw to the right. To decrease it (to weaken it as far as pulling the top thread down, or just giving the advantage, or power, to the top thread), you turn the screw to the left. Just remember, “Righty-tighty, Lefty-loosey”.
Now let’s try to make sense of all of this in easy terms. This is the one and only thing that I make my beginning machine quilting students write down:
“If your bobbin thread is lying flat on the back of your quilt, or you see “eyelashes” from the top thread popping through to the back, you need to INCREASE YOUR TOP TENSION.”
“If your top thread is lying flat on the top of your quilt, or you see “eyelashes” from the bobbin thread popping through to the top, you need to DECREASE YOUR TOP TENSION.”
(I don’t go in to bobbin tension adjustments with my beginning machine quilting students, but the opposite would be true if you wanted to adjust your bobbin tension.)
If this hasn’t put you to sleep, and you’ve actually finished this blog and absorbed some of this information, then I grant you a PhD in Thread Tension! Congratulations. I hope this helps solve some of those thread tension issues for you. I know it can be frustrating, but it’s really just common sense. Remember that “tug-of-war” between the top and bobbin thread, and you should be able to manage both of them with great success!