Whether you are a novice or an expert in sewing, you may have already encountered the annoying problem–thread bunching and tangling under the fabric. You may wonder why the upper thread forms straight stitch but the bobbin thread forms loops under the fabric, and even when you re-thread the lower thread, the issue still persists. This is baffling, isn’t it?
The machine is not threaded correctly
It turns out that most of the time, the reason for thread bunching stems from the upper thread being threaded incorrectly. You should check if the upper thread is threaded correctly, if not, re-thread the machine according to the instruction manual since there is slight variation in the procedure among the models.
Nevertheless, the correct way of threading any sewing machine is similar. First remove the loops under the fabric gently, then re-thread the machine. Make sure that when threading, the presser foot is lifted to let the thread slip into the tension plate and the needle is positioned at the highest level by turning the hand wheel towards yourself. The upper thread should pass through all parts of the thread guide and take-up lever, then through the needle eye in front of the needle and below the hook. The lower thread should also be brought up. Check out the details of threading the machine here.
The thread should pass through all parts of thread guide and take-up lever.
The bobbin is not inserted correctly
If the upper thread is threaded in a right way but the problem still exists, chances are that the bobbin is inserted wrongly. The lower thread is not brought up to the needle smoothly and not in sync with the upper thread. You can check the bobbin case and re-insert the bobbin. The thread should come out from the thread side slot and you should be able to pull it out easily. Check out the details of inserting the bobbin here.
Insert the bobbin in the case by passing the thread side slots.
Wrong thread tension
Incorrect thread tension can also make thread tangled under the fabric as the upper thread does not work well with the bobbin thread. Readjust the tension to see if things improve.
Working with a suitable tension can avoid thread bunching.