How to adjust upper and lower thread tension on a sewing machine

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How many times has your sewing machine started to make stubborn monster-like noises and proceeded to pull your fabric towards the bobbin? Or maybe only managed to sew some you, useless, loose stitches? Do you still think your sewing machine “doesn’t sew knit fabric”?

In this post I am sharing what I know about thread tension. If you have your own tips or you have a different opinion, I would love to hear it!

How to adjust upper thread tension on a sewing machine

Adjusting the thread tension for the thread on top should be a pretty straightforward thing. Or at least it the most obvious tension to play with; getting to know how it actually works and what results you can get by playing with it – is another story.

You adjust the tension of the thread that comes from your thread spool depending on the fabric and thread you’re using.

The tension assembly consists of small discs that squeeze (softer or harder, depending on your adjustments) the thread passing through and another piece called the tension regulator, which keeps that pressure constant. On cheaper or more basic machines you will use a numbered wheel/knob and on newer/more expensive machines you will have a dial or a digital display.

In a nutshell: the higher the number on your wheel/dial, the stronger the squeeze and vice versa. If you use a fine thread your tension should be high; on the contrary when using a thicker or decorative thread, your tension should be lower.

When sewing cottons, you can use a medium-high tension; if a cotton is a loose weave, decrease the tension so you don’t wrinkle your fabric when sewing.

If you’re sewing knit or Lycra, decrease the tension to create a more elastic seam.

Adjusting tension will be easier on some machines than others. Newer machines even self-adjust their top thread tension when changing your thread. If you find yourself going crazy over getting the right tension, check the lower (bobbin tension).

As a general tip: your upper and lower thread should be the same type (acrylic, cotton, silk) and the same thickness.

If that doesn’t work, check if there’s dirt caught inside the tension disks. If you’re brave clean it yourself: decrease the tension to 0, un-thread and unplug your machine and pass a thin cotton rag oiled with sewing machine oil (cooking oil won’t do, get a proper oil for your machine and you’ll thank yourself later) through the disks until all the dirt sticks to the rag. Then adjust back your tension to a medium tension (3 or 4), thread your machine and practice a few seams on a cotton scrap.

How to adjust bobbin tension for sewing with elastic thread

For a long time I didn’t even know you could adjust bobbin tension. I thought there was a lever somewhere and that my sewing machine being a simple, older model didn’t have it. I meddled and twisted and swore at the upper thread tension and had no idea what great relief that little screw on the latch lever can bring.

The latch lever is the part that comes out with your bobbin. The part in which you push your bobbin and through which you take out the thread. There is a small screw near the opening through which the thread comes out and that’s how you adjust the bobbin tension. By unscrewing it you create less tension in the bottom thread; this is a handy adjustment for sewing with elastic thread or thicker thread. Once you’re done with the thick bobbin thread remember to screw it back (always test that the thread comes out comfortably).

Do you have any tips? How do you get the perfect thread tension?

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