In this video, we cover how to adjust bobbin tension, which involves managing both the upper and lower (bobbin) thread tensions. A new bobbin is recommended for the drop test, also known as the yo-yo test. To perform it, we hold the bobbin thread 9 to 12 inches above the hand, ensuring the bobbin doesn't spin freely, then sharply lower and raise the hand. The bobbin should drop about 1 to 1.5 inches. If adjustment is needed, as in our example where the tension is slightly tight, we turn the large recessed screw on the bobbin case in small increments. After making adjustments, it’s helpful to mark the bobbin’s spring contact point with a felt marker and repeat the test to confirm the setting.
We also demonstrate bobbin case adjustment. A one-inch drop is within the ideal range and is particularly useful for cap sewing, where slightly tighter stitches are preferred. Bobbin and top thread tension must be balanced, and consistency is key. We recommend always adjusting the bobbin case to the same drop distance—whether it’s one inch or a bit more—to maintain consistent stitch quality across projects.
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