Bernina USA manufactures a series of sewing machine, including the Bernina QE 440. Although you would hope that your Bernina runs perfectly, problems could potentially include a wrongly positioned needle, a wrongly adjusted tension dial or user error when it comes to regulating the foot pressure. With a little know-how, you can successfully troubleshoot these problems and get your sewing machine running properly again.
Re-position the bobbin if, when tugged, the lower thread does not move smoothly. There should not be too much resistance and the movement should not be forced. Use a small screwdriver to turn the bobbin thread adjustment screw on the bobbin case spring, which can be found inside a panel on the side of your machine. Pull the lower thread again to feel for improvement once you have repositioned the bobbin.
Choose a lower setting from the tension dial if the threads snap under normal working parameters. The higher the number, the greater the tension on sewing machines. Lowering the dial -- which ranges from 1 to 12 -- will, in turn, loosen the thread and reduce the danger of snapped threads. If the tension dial is already at its lowest setting, then the problem of snapped threads must lie elsewhere and you should move on to the next step.
Ensure that the needle is correctly inserted in the Bernina QE 440. It should be toward the back of the Bernina. This position should also reduce the chances of broken threads as you use the machine.
Regulate the firmness of the foot pressure pedal to avoid skipped stitches or irregular feeding. A slower foot pressure speed should avoid skipped stitches whereas faster pressure should remedy irregular feeding. You need to find the correct middle ground.
Remove any clogs or jammed threads if you find that the machine ceases operation suddenly.