Superior Education

The Role of Bobbin Tension

  • Bobbin Tension
  • Bobbin Case
  • Bobbin Thread

How does a bobbin case apply tension?

We often talk about the importance of tension adjustments when using specialty threads, such as Metallic threads. In another education article, we explained that the balance between top and bobbin tension is like a tug-of-war. Both sides exert tension and most often, one side pulls harder and wins.

A bobbin case will apply tension by squeezing a metal plate against the thread as it exists the bobbin case. This plate will raise or lower according to the tension screw. The larger screw in a bobbin case is what will change how much pressure is applied to the thread as it leaves the bobbin case.

Tension adjustments are typically made just for the top thread by adjusting the tension wheel on a home sewing machine (or some home sewing machines have an electric tension control) or by turning the tension knob on a longarm machine. While this adjustment is usually good enough, there are times when it is necessary to loosen or tighten the bobbin tension. If a smooth and fine thread is used in the bobbin, you may need to tighten your bobbin tension. If a thick or heavy thread is used in the bobbin, you may need to tighten your bobbin tension. If you're hesitant to turn the large screw on your bobbin case and affect tension, the safest way to make changes is to take use two bobbin cases. One case for regular sewing or quilting and the other case for specialty threads that can be adjusted.

If your machine has a drop in bobbin case, please read your machine manual before attempting to turn the screw in the case. Most drop in bobbin cases do not require tension adjustments. Most new machines are sold with multiple bobbin cases, one for heavy threads or embroidery and another for sewing and quilting. The recommendation below for tension adjustment applies to a metal bobbin case and is especially applicable to longarm machines.

Bobbin case
The large screw adjusts the tension
Drop in bobbin case
A drop in bobbin case doesn't need tension adjustments

Before making any adjustments to the bobbin case, use a permanent marker and mark a starting point on the metal case. To adjust the tension, turn the large screw in short, quarter-turn increments. To loosen the tension, turn to the left (counter-clockwise). To tighten the tension, turn to the right (clockwise). If you think of the screw like a face of a clock, you should be turning the screw no more than 10-15 minutes. Make a single adjustment at a time, place the bobbin back into the case and stitch. Visually inspect the tension and repeat to make additional adjustments as necessary.

If you are quilting on a longarm machine, a helpful tool to dial in the exact bobbin tension is the TOWA bobbin gauge. This device provides a numerical value for a bobbin's tension setting. It's a fantastic tool and very helpful if you like to switch your top thread often.

Making adjustments to your bobbin tension is a simple process. Learn how to make these adjustments in a quick and easy manner and you'll be able to use a larger variety of threads in your machine.

Learn more about bobbin tension with our Thread Therapy video.
Watch our TOWA video.

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