A lot of the time, embroidery/sewing tension issues can be because of the bobbin case. Many times this is because of a dirty bobbin case. The distance between the bobbin case tensioning spring and the case itself makes it very difficult to clean. Durkee has the solution...the Bobbin Case Cleaner. This product was specifically designed to fit into the difficult to clean areas on the bobbin case to get you back embroidering/sewing quickly.