If bottom thread shows on the top side of the seam, which adjustment is most likely needed for the sewing machine?

• A. Loosen the top thread
• B. Tighten the top thread
• C. Rewind the bobbin
• D. Replace the needle

Answer: (A)

When the bottom thread shows on the top side of the seam, it means the stitch isn’t locking properly because the upper thread is gripping too tightly and pulling the bobbin thread up through the fabric. Loosening the top thread reduces that grip, allowing the two threads to interlock cleanly and keeping the bobbin thread from peeking through on the surface. After making a small adjustment, test on scrap fabric to confirm the balance. If the problem persists, rethread the upper path to ensure it’s correct and check that the needle isn’t bent. Rewinding the bobbin or replacing the needle won’t fix this symptom, since the issue is about the tension of the top thread.