Mary Frederick answered
I will presume you mean the bobbin in a sewing machine. If, I am incorrect, I apologize. Knotting of thread in the bobbin of a Sewing machine is usually caused by one of two problems. First, the thread itself is cotton thread and it is old. Tiny fibers within the thread have deteriorated and they begin to break, and wrap around, the other fibers of the thread causing knots. The other problem and the most common one is the bobbin tension needs to be adjusted.
First, remove the bobbin case and bobbin from the machine, then remove the bobbin from the case. You will need the little screwdriver, which came with your machine tools. If, you do not have this screwdriver, use a small screwdriver like the ones, which come with an eyeglasses repair kit. If, you do not have one of these, you can use the smallest screwdriver you have. Gently, turn the little screw on the side of the bobbin case clockwise just a little, "just a hair" as they say. Gently, pull on the bobbin thread, it should have a little tension, if it seems to lack tension, turn the screw again, "just a hair". Gently, pull on the thread to test the tension. Continue to turn the screw and test the thread until you feel tension.
Place the bobbin into its case making certain to pull the thread through the slit in the case, and pull it through the little opening. Leave about two inches of thread hanging out. Replace the bobbin and make certain your machine is properly threaded. If, t he machine is improperly threaded the bobbin will not lock the thread and you can also break the needle.
Sew a test strip and check the front and back of the strip for the condition of the stitches. If, the bottom reveals solid bobbin stitching your tension is good, if not repeat the process of tightening the bobbin tension. A stitch in time saves nine! Good Luck!
First, remove the bobbin case and bobbin from the machine, then remove the bobbin from the case. You will need the little screwdriver, which came with your machine tools. If, you do not have this screwdriver, use a small screwdriver like the ones, which come with an eyeglasses repair kit. If, you do not have one of these, you can use the smallest screwdriver you have. Gently, turn the little screw on the side of the bobbin case clockwise just a little, "just a hair" as they say. Gently, pull on the bobbin thread, it should have a little tension, if it seems to lack tension, turn the screw again, "just a hair". Gently, pull on the thread to test the tension. Continue to turn the screw and test the thread until you feel tension.
Place the bobbin into its case making certain to pull the thread through the slit in the case, and pull it through the little opening. Leave about two inches of thread hanging out. Replace the bobbin and make certain your machine is properly threaded. If, t he machine is improperly threaded the bobbin will not lock the thread and you can also break the needle.
Sew a test strip and check the front and back of the strip for the condition of the stitches. If, the bottom reveals solid bobbin stitching your tension is good, if not repeat the process of tightening the bobbin tension. A stitch in time saves nine! Good Luck!