Threading the bobbin is a two-step process: winding thread onto the bobbin itself, then placing that wound bobbin into the bobbin case

The bobbin is the small spool that holds thread underneath your fabric. Before you can use it, you wind thread onto it using your machine's bobbin winder — a small wheel or spindle on the side or top of your machine. Once the bobbin is full, you insert it into the bobbin case, which sits below the needle plate. Most machines have the winder and case in slightly different locations, so check your manual for the exact spots on your model.

This process takes about five minutes once you know the steps. The most common mistake is forgetting to engage the bobbin winder before you start, which means the thread just wraps loosely and won't tension correctly when you sew.

Key Takeaways

  • The bobbin winder is usually a small wheel on the side or top of your machine; you must engage it before winding thread onto the bobbin.
  • Wind the bobbin until it is full but not overstuffed — a bobbin that is too full can jam in the bobbin case.
  • The bobbin case sits below the needle plate and holds the wound bobbin; it has a small tension spring that the thread must pass through.
  • Thread the bobbin case by sliding the thread through the tension spring and under the presser foot, then insert the whole case into the machine.
  • If your machine has a drop-in bobbin (no separate case), you place the wound bobbin directly into a slot below the needle plate.

Winding thread onto the bobbin

Start with an empty bobbin — a small plastic or metal spool that came with your machine. Place the bobbin onto the bobbin winder spindle, which is usually a small post on the side or top of your machine. Push the bobbin all the way onto the spindle until it clicks or sits flush; this is important because a loose bobbin will slip and wind unevenly.

Take your thread from the top spool and guide it through the bobbin winder tension disc — a small slot or guide near the spindle. This disc controls how tightly the thread wraps onto the bobbin. Thread the end through the hole in the bobbin itself, then wrap it around the bobbin once by hand to anchor it.

Now engage the bobbin winder. On most machines, you do this by moving a lever or button near the winder, or by turning a dial. Some machines automatically disengage the needle when you engage the winder; others do not. Check your manual to be sure. Once engaged, hold the thread end lightly and press the foot pedal or press start (depending on your machine type). The bobbin will spin and wind thread onto itself.

Stop when the bobbin is full — it should look like a small, evenly packed spool with thread wound all the way to the edge. Do not overstuff it; a bobbin that is too full can jam when you insert it into the case. Most machines have a sensor that stops the winder automatically when the bobbin is full. If yours does not, watch carefully and stop by hand. Cut the thread and remove the bobbin from the spindle.

Inserting the bobbin into the bobbin case (machines with a separate case)

If your machine has a bobbin case — a small metal or plastic housing that you remove and insert separately — follow these steps. First, remove the bobbin case by unlatching it or unscrewing it from below the needle plate. Your manual will show you exactly how; most cases have a small latch or screw on one side.

Hold the bobbin case in one hand with the open side facing you. You will see a small metal arm or spring inside — this is the tension spring. Take your wound bobbin and place it into the case so it sits flat. The thread should be on the outside of the bobbin, facing the tension spring.

Guide the thread under the tension spring by sliding it into the small slot or hook. The thread should sit snugly under the spring; if it is loose, it will not tension correctly and your stitches will be uneven. Pull the thread toward the small notch or opening at the front of the case and slide it through. You should hear or feel a slight click as it seats.

Now insert the bobbin case back into the machine. Align the case with the slot below the needle plate and push it in until it clicks or latches. Pull gently on the bobbin case to make sure it is find. If it moves or feels loose, remove it and reseat it.

Inserting the bobbin into a drop-in bobbin machine

Some machines, especially newer computerized models and many computerized quilting machines, use a drop-in bobbin system. There is no separate case — you place the wound bobbin directly into a slot below the needle plate. These machines are simpler to thread but require a specific bobbin type, so check your manual to make sure you are using the correct bobbin for your machine.

Raise the presser foot and open the bobbin cover — usually a small hinged door or removable plate below the needle. Drop the wound bobbin into the slot, making sure it sits flat and centered. The thread should unwind from the top of the bobbin as it sits in the machine.

Guide the thread through the tension guide or slot — most drop-in systems have a small notch or guide where the thread must pass. Pull the thread gently to make sure it is seated. Close the bobbin cover and you are ready to thread the top of the machine and begin sewing.

Checking bobbin tension before you sew

Before you start sewing, test the bobbin tension by holding the bobbin case (if your machine has one) by the thread and lifting it slightly. The bobbin case should drop slowly — about one inch per second — if the tension is correct. If it drops too fast, the tension is too loose; if it does not drop at all, the tension is too tight.

If the tension is wrong, remove the bobbin case and check that the thread is seated correctly under the tension spring. Make sure the thread is not twisted or kinked. Reinsert the case and test again. If the problem continues, the tension spring may need adjustment, but this is a job for a technician — do not try to bend the spring yourself.

On drop-in bobbin machines, you cannot test tension this way. Instead, sew a test seam on scrap fabric and look at the stitches. If the bobbin thread is showing on top of the fabric, the bobbin tension is too loose. If the top thread is showing on the bottom, the bobbin tension is too tight. Adjust the bobbin tension dial (if your machine has one) and test again.

Common mistakes and how to avoid them

The most frequent error is forgetting to engage the bobbin winder before you start winding. If you wind without engaging the winder, the thread wraps loosely and will not stay on the bobbin when you try to use it. Always check that the winder is engaged — you should hear a click or feel resistance when you press the foot pedal.

Another common mistake is threading the bobbin case incorrectly. The thread must pass under the tension spring, not over it or around it. If the thread is not under the spring, it will not tension correctly and your stitches will be loose or uneven. Take your time guiding the thread through the slot and make sure you hear or feel it seat.

Overstuffing the bobbin is also common, especially if you are winding by hand or if your machine does not have an automatic shutoff. A bobbin that is too full can jam in the case or cause the thread to tangle. Wind until the bobbin looks full but not bulging, and stop if you feel resistance.

Finally, do not force the bobbin case into the machine. If it does not slide in smoothly, remove it and check that the bobbin is seated correctly inside the case and that the thread is not caught on anything. A case that is forced in can damage the latch or the machine itself.

Frequently Asked Questions

What type of bobbin does my machine use?

Check your machine's manual — it will show you the exact bobbin type and size. Most machines use either a Class 15 bobbin (the most common size) or a Class A bobbin (slightly smaller). Bobbins are not interchangeable, so using the wrong type can cause jamming or tension problems. You can also take your machine to a fabric store and ask them to match your bobbin.

Can I use a plastic bobbin instead of a metal one?

Yes, most machines accept both plastic and metal bobbins. Plastic bobbins are lighter and less likely to rust, but metal bobbins last longer and hold tension more consistently. Check your manual to see if your machine has a preference. If you switch between plastic and metal, you may need to adjust the bobbin tension slightly because they wind differently.

My bobbin thread keeps breaking. What am I doing wrong?

Bobbin thread usually breaks because the tension is too tight, the bobbin is overstuffed, or the thread is not seated correctly under the tension spring. Remove the bobbin case and check that the thread is under the spring, not twisted or kinked. If the thread is correct, try loosening the bobbin tension slightly. If the problem continues, the bobbin case may be damaged — take it to a technician.

Do I need to wind a new bobbin every time I change thread color?

Yes, if you want the bobbin thread to match the top thread. However, if you are sewing with a color that will not show on the back of your fabric, you can leave the old bobbin in and just change the top thread. For most projects, it is easier to wind a fresh bobbin so the colors match and you do not have to think about it.

What happens if I thread the bobbin case backwards?

If you insert the bobbin case upside down or backwards, the thread will not seat under the tension spring correctly and your stitches will be loose or uneven. The machine may also jam. If you notice loose stitches after threading, remove the bobbin case and check that it is oriented correctly — the latch should be on the side that faces the machine body.