The thread tension is incorrect.
There could be several reasons why the tension won't set on the machine.
- Check the machine is threaded correctly. Rethread the machine according to the instructions in the manual.
Refer to "Upper threading" of "Preparation" category.
- Check the upper thread tension set.
- Remove the bobbin and make sure it is threaded properly in the shuttle race.
Refer to "Correctly installing a bobbin. " of "Preparation" category.
- If there is any loose thread or lint in the bobbin case, please clean them with the included cleaning brush.
Refer to "Cleaning the Bobbin Case" of "General Information" category.
- Check if the combination of needle size, thread size and fabric is incorrect. Be sure to use the correct needle and thread size for the fabric you are sewing.
(Example: Denim-size 16 needle and 40-50 heavy duty thread)
Refer to " Combination of fabric, thread and needle " of "General Information" category.
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