Thread TensionProper adjustment of thread tension is one of those skills that you must learn in order to sew. Each machine will have its own "best" adjustment. Remember that this "best" adjustment is also affected by the material you are sewing on, the stitch type, and the thread you are using. A change of any of those MAY require readjustment of your upper and lower thread tension. All Machines come out of the factory with a "normal" range of adjustment that works fine for most people on most fabrics using most stitches and most threads. If your project requires a tension adjustment beyond the "normal" range, see your Sewing Machine Technician who will adjust the machine to your needs.Upper tension and lower tension must always remain balanced to produce a perfect stitch. The upper tension adjustment may be on the face plate, on the face of the needle-bar housing, on the front of the needle-bar housing, or on the upper arm of the machine head. REMEMBER THAT THE UPPER THREAD MUST BE THREADED CORRECTLY PER INSTRUCTIONS. If you miss the upper tension discs, you will have no upper tension no matter what the upper tension indicator shows.The lower tension, located on the shuttle or bobbin case, is usually adjusted by a screw. If two screws fasten the lower tension spring to the bobbin case, adjust by turning the screw nearest the center of the spring. Make all adjustments on the upper tension first before adjusting the bobbin tension.
If the lower tension is questionable, adjust both lower and upper tensions so that there is a slight drag on each thread. Use the same size thread on both bobbin and spool. Adjust the tension, and examine the stitching that the machine makes. Use contrasting colors of thread on the top and in the bobbin to help you to see the stitches clearly. Set stitch-length control for a medium length of stitch.OK, Let's look at the stitching. In a perfect stitch, threads are locked in the center, midway between the two layers of cloth, with no loops on the top or bottom of the seam and no puckers in the cloth. See Below Figure. |
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Perfectly Locked Stitch |
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If loops of the bobbin thread show on the top side of the seam and the top thread is straight, the upper tension is tighter than the lower. In this case, loosen the top tension. See Below Figure. |
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Upper Tension is Too Tight |
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If loops of the spool thread show on the underside of the seam and the lower thread is straight, the upper tension is looser then the lower and should be tightened. See Below Figure. |
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Upper Tension is Too Loose |
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Remember that your machines "best" adjustment is also affected by the material you are sewing on, the stitch type, and the thread you are using, and that any change to those MAY require readjustment of your upper and lower thread tension. If your project requires a tension adjustment beyond the "normal" range, see your Sewing Machine Technician who will adjust the machine to your needs.
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