Loose stitches or knots on the underside of the material

The lower thread lies straight on the underside of the material and there is the appearance of loops or small knots.

Possible Causes and Solutions:

Cause: The tension of the upper thread is too weak or the tension of the lower thread is too tight.
Solution: Tighten the tension of the upper thread, or loosen the tension of the lower thread, until the tensions of both threads are correctly balanced.

Cause: The machine is not threaded correctly.
Solution: Re-thread the machine correctly according to the instruction manual or video.

Cause: The thread is caught or stuck at the thread spool
Solution: Verify that the thread is not caught or stuck at the thread spool, thread stand or thread guides.

Cause: The bobbin base is not threaded correctly. The bobbin unwinds itself in the wrong direction.
Solution: Thread the bobbin base correctly.

Cause: The point of the needle is bent.
Solution: Replace the defective needle with a new one.

Cause: The bobbin is not evenly wound. It unwinds itself irregularly.
Solution: Replace the bobbin with one that is wound evenly.

Cause: Lint or dirt in the bobbin base prevents the bobbin from revolving freely.
Solution: With a pointed pin remove all dirt from this part. Clean with kerosene and dry thoroughly before replacing in the machine.

Cause: The thread take-up spring (check spring) is not adjusted and does not work properly.
Solution: Adjust the thread take-up spring until it has the correct tension and its upward motion is just finished at the moment the needle enters the material.