1 thread that is inaccurate or of poor quality. You might be using a stretchy fabric with non-stretch thread. 2: Incorrect presser foot; using the improper foot, such as the buttonhole or appliqué foot, may result in puckering.
Stitching bits of cloth together can allow you to check the thread tension. The correct thread tension is required for optimal stitch creation during sewing. A tension that is too loose will cause the stitches to unravel, while a tension that is too tight will cause the cloth to pucker. To adjust the thread tension, first make sure the feed dogs are down. Then lift the presser foot up or away from the bed of the machine.
You must do this with care so as not to damage any parts of the machine. Once adjusted, the thread tension should remain constant until it wears out or is changed by a technician.
The best way to check the thread tension is to grab a piece of fabric and some thread and have a go at stitching something up. If the stitch quality isn't good enough and it doesn't hold its shape, then you need to change the thread tension.
Different types of machines require different amounts of tension to produce satisfactory results. If you aren't sure how much tension to use, follow these simple guidelines:
For light-to-medium weight fabrics, set the tension screw to about 3/4 of the way down. This should be sufficient to create decent seams without pulling the threads too tight.
For heavy fabrics, set the tension screw to all the way down.
A large nest of twisted thread is frequently the consequence of an incorrectly threaded sewing machine. Don't blame the bobbin just because the tangled mess is on the bobbin side of the sewing. To resolve this issue, raise the presser foot and completely unthread the sewing machine. Remove the bobbin case and clean out any lint or debris that may be caught in the moving parts.
After cleaning out the interior of the bobbin case, reassemble the unit and test to make sure the jam does not happen again. If it doesn't, replace any worn or broken parts such as the top hook, bottom hook, or tension rod.
Examine the threading on your system. Unthread and rethread your sewing machine completely. Upper threading faults are frequently the source of a knotted thread on the bottom side. Check the bobbin to ensure it is properly threaded and that the bobbin casing is properly threaded. If these are correct, then double check the top threading on the machine. Lower threading faults are more difficult to identify without removing the cover from the machine. However, if you see small bits of fiber or fuzz in the loop formed by the lower thread, this is probably the cause of your problem.
If your sewing machine is more than 10 years old, consider replacing it with a new model. Older machines tend to be heavier duty than today's models, so they're capable of handling thicker threads and fabrics. Also, modern machines come with automatic stop mechanisms that shut off the power supply to the motor when something is out of place with the threading. Older models had only manual shut-off switches, so threading errors were likely to result in damaged fabric or a broken needle setter mechanism.
A clogged feed dog can prevent the feeding mechanism from engaging the next stitch, resulting in a skipped stitch. This will cause a hole in one area of the seam where the feed dog should be and an open space where the stitch was supposed to go. You may be able to fix this problem by cleaning the feed dog mechanism.