Unfortunately, you can't directly adjust the lower tension (bobbin tension) on most Brother sewing machines. Lower tension is pre-set at the factory. However, adjusting the upper thread tension often resolves issues that appear to be related to the lower tension.
The provided reference explains how to adjust the upper thread tension, which indirectly impacts the balance of the stitch and is the method you'll likely use to correct most tension problems.
Here's how to address tension issues on your Brother sewing machine by adjusting the upper thread tension:
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Identify the Problem: Examine your stitching. If the upper thread is visible on the underside of the fabric, it means the upper tension is too tight (or the lower tension appears too loose).
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Adjust the Upper Thread Tension:
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Loosen the Upper Tension: Turn the thread tension dial to a lower number (toward the left). This loosens the upper thread tension. According to the reference, lowering the number on the dial loosens the thread tension.
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Tighten the Upper Tension: If the bobbin thread is visible on the top side of the fabric, turn the thread tension dial to a higher number (toward the right). This tightens the upper thread tension.
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Test and Repeat: Sew a test swatch after each adjustment to see if the problem is corrected. Make small adjustments until the stitching is balanced, with the knots from both threads meeting within the layers of fabric.
Important Considerations:
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Threading: Ensure your machine is properly threaded. Re-threading both the top thread and the bobbin is a good first step in troubleshooting tension issues.
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Bobbin Winding: Make sure the bobbin is wound evenly. Uneven winding can affect tension.
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Thread Quality: Use good-quality thread. Old or cheap thread can cause tension problems.
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Needle: Use the correct size and type of needle for your fabric. A damaged needle can also cause tension issues.
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Lint Build-up: Clean your machine regularly. Lint accumulation can interfere with tension.
When to Seek Professional Help:
If you've tried adjusting the upper thread tension and the problem persists, there might be an issue with the lower tension assembly that requires professional servicing. Avoid attempting to adjust the bobbin case tension screw yourself unless you have experience, as this can easily damage your machine. Consult a qualified sewing machine technician.
