How should you test and adjust thread tension on a parachute sewing machine before production?

• A. Guess tension by feel and proceed.
• B. Use a pre-set tension and never test.
• C. Adjust only bobbin tension and ignore top tension.
• D. Sew on scrap fabric, observe stitch balance, adjust top and bobbin tensions until even stitches.

Answer: (D)

Testing and adjusting thread tension on a parachute sewing machine starts with the idea that balanced stitches come from correct interaction of both top and bobbin tensions. To get reliable, repeatable results before production, sew on scrap fabric that matches the production material, using the same thread, needle, and stitch pattern. Look at the stitched seam from both sides: balanced stitches mean the appearance on the top and the underside are even, with the threads interlocking neatly in the fabric and no loose loops or puckering. If the top looks too tight or the bottom shows loose stitch formation, you adjust the corresponding tension and re-test. Repeat until you achieve stitches that look the same on both sides and hold properly under the expected load.

This approach is essential because it provides a reproducible setup, detects issues before committing to lots of production, and ensures the fabric and thread work together safely. Slipping into a preset, untested tension risks unpredictable seams, fabric damage, or failure under load. Limiting adjustments to only one tension or guessing by feel will not produce reliable results, which is unacceptable for parachute gear that must perform in critical conditions.