When the bobbin thread breaks, check the following possible causes and solutions.

• The bobbin thread was not set correctly.
  
  Reset the bobbin thread correctly.
  For details on setting the bobbin thread, refer to "How do I install the bobbin wound with thread?".
  
  
   
• Bobbin thread is incorrectly wound.
  
  Rewind the bobbin thread correctly.
  For details on  winding the bobbin, refer to "How do I wind the bobbin?".
  
  
   
• There are scratches on the bobbin.
  
  Replace the bobbin with a new one.
  
  
   
• The thread is tangled.
  
  Remove the tangled thread and clean the race.
  
  
   
• A bobbin designed specifically for this machine is not used.
  
  Incorrect bobbins will not work properly.
  Be sure to use the included bobbins (part code: SA156, SFB: XA5539-151) or the same type.
  SA156 is Class 15 type bobbin.
  The bobbin's height is 11.5 mm (approx. 7/16 inch).

  (1) 11.5 mm (approx. 7/16 inch)