Threading a bobbin is a three-step process: wind thread onto the bobbin, insert the bobbin into its case, and thread the case through the tension discs
A bobbin holds the thread that forms the underside of your seam. If your bobbin is empty or you are switching thread colors, you need to wind new thread onto it and then place it in the machine so the thread feeds correctly. The exact steps depend slightly on whether your machine uses a top-loading or front-loading bobbin case, but the principle is the same on nearly all machines.
This guide covers the most common setup: a machine with a removable bobbin case that sits inside the machine's hook assembly. If your machine has a built-in bobbin area with no removable case, check your manual for the specific path the thread takes, but the winding step is identical.
Key Takeaways
- Wind the bobbin on your machine's winding mechanism before you insert it into the case, using the same thread color and weight you plan to use on top.
- The bobbin case has a small tension spring with a slot; thread the bobbin thread through that slot so it sits under the spring.
- Insert the loaded bobbin case into the machine's hook assembly with the thread tab pointing toward the needle, then lower the presser foot to set the tension.
- If stitches loop on the underside of your fabric, the bobbin thread is usually too loose; if they loop on top, the bobbin tension is too tight.
Winding thread onto the bobbin
Place an empty bobbin onto the bobbin winder spindle, which is usually a small metal rod on the top or side of your machine. The spindle has a notch or groove; slide the bobbin onto it so the groove aligns with the spindle's pin. The bobbin should sit flat and not wobble.
Pull thread from your spool and wrap it around the bobbin two or three times by hand, going in the same direction the bobbin will spin. This anchors the thread so it winds evenly. On most machines, you then guide the thread through a small tension disc on the bobbin winder (a metal or plastic piece that looks like a tiny clamp). Check your manual to see if your machine has one and where it sits.
Press the bobbin winder against the machine's body or press a button to engage it, depending on your model. The bobbin will spin and wind thread automatically. Stop when the bobbin is full—most machines have a sensor that stops the winding automatically, or the bobbin will slow down noticeably. Do not overfill; thread wound past the bobbin's rim will catch on the case.
Cut the thread and remove the bobbin from the spindle. You now have a wound bobbin ready to insert into the case.
Inserting the bobbin into the case
Remove the bobbin case from the machine. On most machines, it hangs inside the hook assembly below the presser foot. Look for a small latch or lever on the case; pull it toward you or lift it to release the case. The case will slide out. If you are unsure where it is, check your manual or look for a small metal or plastic box hanging below the needle area.
Hold the bobbin case in one hand with the open side facing you. You will see a small metal spring inside with a slot cut into it. This is the tension spring. Insert the wound bobbin into the case so the thread unwinds from the top of the bobbin (the same direction it wound on). The thread should unwind smoothly when you pull it gently.
Guide the thread through the slot in the tension spring. The thread sits under the spring, held in place by the spring's tension. Pull the thread gently; it should resist slightly. If it pulls freely, the thread is not seated correctly in the slot—reposition it so the spring holds it firmly.
Leave about 4 to 6 inches of thread hanging from the case. You will use this to catch the top thread later.
Placing the bobbin case back into the machine
Hold the bobbin case so the thread tab (the part where the thread exits) points toward the needle. On most machines, this means the tab points to the left or toward the front. Slide the case back into the hook assembly, pushing it in until you hear or feel a click. The latch should engage automatically, or you may need to flip a lever to lock it in place.
Lower the presser foot all the way down. This is a critical step: lowering the presser foot opens the tension discs on top of the machine, allowing the top thread to sit between them correctly. If you thread the top thread without lowering the presser foot, the tension will be wrong and your stitches will be uneven.
Bringing up the bobbin thread
Hold the top thread (the one coming from your spool) loosely in your left hand. Turn the handwheel toward you (the large wheel on the right side of the machine) one full rotation. As you turn, the needle will go down and come back up, and it will catch the bobbin thread and pull a loop to the surface.
When the needle comes back up, you will see a loop of bobbin thread on top of the fabric or on the needle plate. Pull the top thread gently and the loop will come free. You now have both threads on top of the machine, ready to thread into the needle.
Pull both threads toward the back of the machine and under the presser foot. This keeps them out of the way and prevents them from tangling as you begin to sew.
Checking your bobbin tension
Sew a test seam on scrap fabric using the same weight of fabric you plan to use for your project. Look at both sides of the seam. The stitches should look the same on top and bottom—a balanced line of thread with no loops or knots.
If you see loops on the underside of the fabric, the bobbin thread is too loose. The bobbin tension is controlled by a small screw on the bobbin case itself. Turn the screw a quarter turn clockwise (to the right) to tighten it. Test again. Make only small adjustments; a quarter turn makes a noticeable difference.
If you see loops on the top of the fabric, the bobbin tension is too tight. Turn the screw a quarter turn counterclockwise (to the left). Again, test after each adjustment. Most machines come with the bobbin tension set correctly, so you should rarely need to adjust it unless you are using very heavy or very light thread.
Common mistakes to avoid
Threading the bobbin backward. The thread should unwind from the top of the bobbin, the same direction it wound on. If it unwinds from the side or bottom, the thread will not feed smoothly and may tangle.
Forgetting to lower the presser foot before threading the top thread. The presser foot controls the tension discs. If you thread with the foot up, the discs are open and will not grip the thread, making your stitches loose and uneven.
Overfilling the bobbin. Thread wound past the rim of the bobbin will catch on the case as it spins, causing the thread to break or jam. Wind until the bobbin is full but not bulging.
Not seating the thread in the tension spring. If the thread sits on top of the spring instead of in the slot, the tension will be wrong. The thread should be held firmly by the spring so it resists when you pull it gently.
Frequently Asked Questions
Can I use a different color thread in the bobbin than on top?
Yes. The bobbin thread shows on the underside of your seam, so you can match it to the back of your fabric or use a contrasting color for decorative effect. Use the same weight of thread as your top thread so the tension stays balanced.
What if my bobbin thread keeps breaking?
Check that the thread is wound evenly on the bobbin with no loose loops or knots. Make sure the thread is seated in the tension spring slot and not pinched or twisted. If the bobbin is old or damaged, wind a new one. If the problem continues, the bobbin case may be bent; take it to a repair shop to have it checked.
Do I need to rewind the bobbin every time I change the top thread?
Not if you are using the same color. You only need to rewind when the bobbin runs out of thread or when you want to switch to a different color on the underside of your seam.
Why does my machine have two bobbin cases?
Some machines come with a spare bobbin case so you can keep one wound and ready while using the other. This saves time if you switch colors frequently. Both cases work the same way.
What if I cannot find the bobbin case on my machine?
Some newer machines have a top-loading bobbin that sits in a compartment above the needle rather than hanging below. Check your manual for the location and threading path. The winding step is the same, but the insertion method differs.