(Previously appeared on a sewing blog)
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When you sew, your needle goes into the fabric and hooks the thread coming from the bottom and locks it with the top thread and you have a stitch. The amount of thread that is used for this stitch, specifically the amount of thread that passes through the machine and down to your needle, is called thread tension
Sewing machine tension is very important when you are sewing because if your tension is not set right, your sewing machine will lose its ability to sew a good stitch. Most of the time you don’t have to worry about tension. Especially when you are sewing with common materials like cotton. However, when you get to material like knit or elastic, things get tricky.
The quality of your stitch comes down to the amount of thread that is flowing down to the needle. If there is too much, the stitch is very loose. If there is too little, the stitch is very tight. How do you control this flow?
For me, the last thing I want to do is mess with my sewing machine’s tension. I have never been able to understand the whole concept of tension. What is sewing machine tension and how do you adjust it to work with different fabrics?
Most sewing machines have a dial somewhere on the machine, sometimes it is a dial on the top of your machine or a knob in the middle. Wherever it is, this dial controls tension disks that press down on the thread while you are sewing.
To sew a good stitch, you need to control the tension of the top and bottom threads so that they work together in a balanced way and interlink exactly at the middle of the fabric. If there is no balance between the threads, one will pull the other through the opposite side of the material. The top thread will pull down to the bottom or the bottom thread will pull to the top.
This imbalance not only doesn’t look right but you will have a stitch that will probably come undone easily.
The bottom stitch is controlled by the bobbin tension and that is usually set at the factory and often times does not need to be reset even though you are sewing different types of material. I’m not saying that you won’t ever need to set the bottom bobbin tension. There will eventually be a time when you have to reset the tension but most likely, it will be the top thread tension that needs to be adjusted.
Working together
It’s not just one dial that affects the thread tension on your machine. You have several tension tools on your machine that work together to run the right amount of thread through your machine. Here is a list of the tension tools on your machine:
1. Thread guides
2. Tension discs
3. Tension regulator
4. Bobbin-case spring
Thread guides are important because they help you to thread the machine correctly. Always follow the directions on your machine to thread correctly. So many times, tension problems happen because you did not thread your machine properly. It can happen if you are tired or if you are new to your machine.
It is so important that the thread goes through the tension discs that are located inside your machine. You bring your thread down from the top and you loop it through the groove that gives the tension discs access to your thread. The tension discs put pressure on the thread as it passes through.
The tension regulator works with the discs to control the amount of pressure on the discs. Together the tension discs and the tension regulator are called the tension assembly.
On older machines there are only two tension discs and on newer ones there are three. The older machine controls the discs with a knob and the newer machines control the discs by a dial or a keypad, usually on the front of the machine.
The way you know how to adjust the tension is to follow the numbers on the dials. Here is the important thing to know about the tension regulator, if the tension is adjusted to a higher number the disc move close together and apply more pressure to the threads. If the tension is adjusted to a low number, the discs move further apart to decrease the pressure on the threads.
The thread guides play an important part in achieving thread tension because it offers a bit of resistance, and this helps the thread to flow correctly through the tension discs and achieve a good and balanced tension.
How to adjust tension
If your stitch is smooth on both sides of your fabric, you don’t have to worry about the tension. It is in balance and nothing else must be done. But we aren’t always so lucky with stitches. Unbalanced tension in the stitches could be evident when there are visible loops or knots at the end of a stitch.
The side where the knots and loops are evident gives you a clue as to what tension needs to be adjusted. If the knots and loops are visible on the wrong side of the fabric the needle tension is very loose and perhaps the bottom bobbin tension is too tight. The opposite is true when the loops or knots are on the right side of the fabric – top too tight, bottom too loose.
If both tensions are too tight, you get stitches that pucker the fabric or even stitches that break really easily. At this point, you stop sewing point, you need to stop what you are sewing and investigate what is going on with your machine.
The best thing to do is to take a sample piece of material and start to adjust the tension a little bit at a time. When you sew a few stitches, you will either see the knots and loops get worse or get better. Keep moving the dial in increments until you get a balanced stitch.
Stretch material
When you are working with elastic and stretchy materials you have a looser weave and that is important when you think of the needle piercing your material and reaching to hook the bottom thread. Not all knits are the same. You have lightweight knits and heavy weight knits. Here are some examples of different knit materials:
1. Jersey knit
2. Rib knit
3. Interlock knit
4. French Terry knit
5. Fleece knit
These knits are distinguished by the way they are “knitted” together. In other words, it is all in the looping of the fabric and these loops can be tight or loose. Knit is a textile that inter-loops or inter-meshes loops. This is different than fabrics that are woven together.
In a woven fabric the threads are weaved together in a straight line that run parallel either lengthwise or crosswise but yarn in knitted fabrics follow an up and down path that forms symmetric loops above and below. It’s kind of like a meandering path created by loops that can stretch and be elastic.
This is a simplistic way of explaining knit and elastic materials. Not all knits are created the same. For example, you have lightweight and heavyweight knits that both stretch but have a different type of loop composition.
The most important thing to know is that knit material is different than woven material and so you need to make adjustments when sewing.
Correct tension for material
The first thing you need to do when sewing a knit fabric or elastic is to test your material. Elastic is kind of tricky to sew because it is denser than most fabrics. First of all, use a zig zag stitch to sew elastic and lower your tension.
The thing to know with elastic is what material you are sewing it on to. Is it a woven piece of material or a knit material? This can dictate the tension that you need to use on your machine. Also, the trick with elastic is the 3-8% stretch while you are sewing the elastic onto the garment. Specifically, the more you stretch, the more stitches you are putting into the elastic.
If you are sewing a stable knit, lower your tension to 2 or 3. If you have a heavyweight knit, you will adjust your machine to around 4. For medium weight fabrics, a 4-5 tension range is suggested. If you have to go higher to a six, your machine might need to be serviced.
But here is the thing, tension is a relative thing. The setting of your tension is really going to depend on your machine. The numbers above are only a general suggestion. The thing to do is slowly test your stitch on a sample fabric. Slowly test means to try one setting, sew and observe for loops and knots on the top or the bottom of your fabric.
I have sewn knits without having to adjust my tension, but I have also run into major problems when I don’t adjust my tension. Look at your fabric first and determine the amount of stretch you are dealing with. The stretch gives you a clue to whether the loops are tight or loose.
Think of the interlock that the stitch will have to achieve. If your material is loose and your fabric is thin, you are going to help that lock happen. Stick to the lower numbers and if the material is tighter and thicker, stick to the higher numbers.
The trick is to test the material first and gather information or clues as to what to set your tension at.
What about the bobbin?
If you have a drop-in style bobbin, chances are you won’t have to adjust the bobbin tension. Usually, the factory setting is good for most sewing situations. However, sometimes you will need to adjust the bobbin tension on a drop-in-style bobbin, although this is a rare occurrence.
If you have a front-loading bobbin, with its own case that can be removed, the little, tiny screw that controls everything could have been moved – even by accident. It’s just the nature of the location and position of the front-loading bobbin.
When sewing stretchy material, you may not run into a problem with the bottom thread. If you want to check the bobbin tension before you start to sew do the following:
1. Insert bobbin into bobbin case
2. Hold the bobbin case by just the thread. There should be no movement in the bobbin case.
3. Pull on the thread a little bit to see if the bobbin case slides down a little bit – if it does than the tension is perfect.
4. If the bobbin case moves too freely then the tension is too loose
5. If the bobbin case doesn’t move at all – the tension is too tight.
If you have to adjust the bobbin tension, do so methodically and keep good notes on what you are doing in case you have to reverse your methods.
Overall, don’t be afraid of having to adjust the tension on your machine. Just be mindful of what you are doing and take it slow. Good luck and happy sewing!