Adjusting the bobbin tension is not always a requirement, but it can help you fine-tune your stitching. The bobbin should already be set to a standard tension, but if you are using a thicker or finer than normal thread, making adjustments can help your project. The 5050C sewing machine by Singer stores its bobbin in a compartment on the base so it is easier to get to and quickly make the proper changes.
Open the bobbin door and remove the bobbin from the compartment.
Use the screwdriver to tighten or loosen the screw on the side of the bobbin while holding it in your hand. Turn it slightly and slowly. Turning it to the right will increase the tension on the bobbin; turning it to the left will loosen the tension.
Stop adjusting the bobbin when the thread in the bobbin can be pulled firmly to where it can just barely be pulled through the bobbin.
Replace the bobbin back in the compartment and close the cover.