bobbin thread showing

Check the tension of the bobbin thread. Also check your bobbin holder. You can also try re-winding your bobbin thread.

Chances are the tensioner on your bobbin holder has build up in it which does not allow for the tensioner to apply the tension correctly on the bobbin thread.

Remove the bobbin use the side of a business card and slide under the tensioner to remove the build up, then re-insert the bobbin and do a tension test. Thread the bobbin as normal except for the pig tail, hold the bobbin thread only and do a slight jerk, the bobbin in its case should not be able to unroll with only its weight that means the tensioner is to loose. What you are looking for when you do the small jerk is only a couple of inches of the bobbin to release. That is a good starting point for tension, finish threading through the pigtail and test.

The bobbin cases should be cleaned daily and tension checked, if running full eight hours a day clean them half way through. What we do in our business is have more than enough extra bobbin cases cleaned and ready to go at all times.

Change the bobbin.....if it solves the problem, it means the previous bobbin tension was loose.

If it still gives you the same problem then the cuase could be that the bobbin tension is loose which is why the top thread is pulling it up so you need to tighten the bobbin tension and at the same time loosen the tension of the top thread which might be tight.