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Imagine this scenario – you’ve got a brand new project to make and you just can’t wait to get sucked in. You’ve threaded your machine with a brand new reel, you’ve changed your needle, and your fabric pieces are cut and ready to sew. You begin your first seam and… disaster! Why do the stitches look so strange? They’re totally different on the front and back of the fabric, and one side looks like it hasn’t worked at all. Why aren’t they neat and tidy like usual? The answer may well be simpler than you think – it could be a tension issue.
What Is Tension?
In the world of sewing, ‘tension’ refers to the delicate balance between your upper thread and your bobbin thread. In an ideal world, they will be perfectly aligned, leading to flat, neat stitches that look the same on the right and wrong sides of your fabric.
Think of it like a tug of war – if both teams are equally balanced, the rope won’t pull in either direction. However, if one team is stronger, the rope will quickly shift over to their side. The tension between your upper and bobbin threads works in much the same way.
Several factors can throw off this delicate balance, leading to a number of different issues – which we’ll dive into below.
What’s the Main Cause of Tension Issues?
There are plenty of things that can throw off the balance of your sewing machine tension, but the first port of call should always be to check your tension settings.
First, Check Your Upper Thread
As it works its way through the machine, your upper thread passes through a set of tension discs, which are usually controlled by a numbered dial. This allows you to turn the upper tension up or down, depending on your project.
As a general rule, the majority of projects need an upper tension of around 4 or 4.5, but this can differ based on things like the thickness of the material you’re working with, and the type of thread you’re using. Typically, thicker fabrics will need a slightly higher tension, and delicate fabrics will need a lower one. Always test your tension settings with the same fabric and thread you’ll use in your final project to ensure everything is set up correctly.
What About the Bobbin?
The bobbin thread tension should be left alone whenever possible, but in rare cases, it may also need a slight tweak. To do this, remove your bobbin case from your machine and gently tighten (or loosen) the screw that sits on the side of it. This should be done carefully, in very small increments.
To test your bobbin tension, load a fresh bobbin into the case and hold the thread tail that comes out of it between your index finger and thumb, about a foot or so above your work surface. While still holding the thread (but not the bobbin case), gently flick your wrist – almost as if you were spinning a yo-yo. Now, observe what your bobbin case does:
- If the case feels loose and drops right down onto your work surface without resistance, your tension is too low.
- If the case stays where it is and doesn’t move at all, your tension is too high.
- If it drops slightly then stops after a couple of inches – congratulations, your tension is correct!
You may also find that as you flick your wrist the bobbin falls out of the case completely – don’t worry, this isn’t an indication of bad tension. It just happens sometimes! Simply re-load your bobbin, and try again.
What Else Can Affect It?
If your tension settings look to be correct but the machine is still misbehaving, there could be a few other problems at play, such as:
Is the upper reel threaded correctly?
This is perhaps the number one culprit to disrupt an otherwise well-tensioned machine. Remove your upper reel completely and re-thread it, taking the time to ensure every step of the process is performed correctly. If needed, you can check how to thread your machine properly in its user manual.
Is the bobbin threaded correctly and fitted into place?
Just like your upper thread, your bobbin can also cause problems if it isn’t threaded correctly. Make sure that it’s inserted into the case properly, and that the case is seated accurately within its shuttle. It’s also important to use the machine’s bobbin winder feature to thread the bobbin properly – it needs to be even and neatly wound, so don’t try to do it by hand.
Did you thread your upper reel with the presser foot up?
The tension discs of your machine open slightly when the presser foot is up, and close into their final position when it’s down. Make sure to thread your upper reel with the presser foot up, to allow the thread to slide between the tension discs neatly and correctly.
Has your machine been serviced recently?
Every project you sew generates a small amount of fluff and this, along with other dust and debris, can quickly snarl up the mechanism of your machine. Keep the areas you can reach clean and tidy and remove excess fluff from the needle plate and the bobbin shuttle regularly as you work. You should also keep your machine well oiled, and have it professionally serviced every one to two years.
How Can You Tell That Your Tension Is Off?
There are two main ways that incorrect tension will present itself:
- If the bobbin thread shows on the top side of the fabric: Your upper thread tension is too tight (or your bobbin thread is too loose).
- If the upper thread shows on the underside of the fabric: Your top thread tension is too loose (or bobbin thread is too tight).
Try adjusting the upper tension first by turning your regulator dial up or down accordingly, then work another test to check the results. Always adjust the upper tension before attempting to change the bobbin tension – 99% of the time, the upper is the one causing the issue. Make sure to only adjust your tension dial by a small amount at a time – even tiny increments can change the outcome of your project.
We hope this guide has been helpful – and remember, always test your settings before starting a new project to ensure the best results. Happy sewing!