The bobbin goes in the bobbin case, then the thread loops under a small metal lever
The bottom thread on your sewing machine lives in a removable metal or plastic holder called a bobbin case. The bobbin itself is a small spool that holds the lower thread. To thread it, you insert the bobbin into the case, then guide the thread under a tension lever — a thin metal arm with a slot — before closing the case back into the machine. The exact position of that lever and the steps to access it depend on whether your machine has a drop-in bobbin or a removable bobbin case, but the principle is the same on nearly all machines.
Threading the bottom correctly takes about one minute once you know where the tension lever is. A mistake here shows up when ready in your stitches: loose loops on the underside of the fabric instead of tight, even seams. The good news is that you can fix it without rewinding the bobbin or starting over.
Key Takeaways
- The bobbin case sits either directly under the needle plate (drop-in style) or pulls out from the side of the machine (removable style).
- The thread must pass under the tension lever inside the bobbin case before you close it, or the bottom thread will be loose and uneven.
- If you cannot see the tension lever, check your machine's manual — some cases have the lever on the outside, others on the inside.
- A correctly threaded bobbin case will hold the thread snug when you pull it gently; if it slides freely, the thread is not under the lever.
Drop-in bobbin machines: the most common type
If your bobbin case is built into the machine and you access it by lifting the needle plate, you have a drop-in system. First, raise the presser foot — this opens the tension discs on the bobbin case. Wind your bobbin on the top of the machine and insert it into the case with the thread wound clockwise (the direction matters). The bobbin will sit flat in a circular recess.
Now locate the small metal tension lever on the bobbin case itself. It looks like a thin arm with a notch or slot cut into it. Pull the bobbin thread so it lies flat, then guide it under that lever from left to right. You should feel slight resistance as the thread slides under. Pull the thread gently — if it holds with a little tug, you have threaded it correctly. If it pulls out easily, the thread is not under the lever and you need to try again.
Once the thread is under the lever, leave a 4- to 6-inch tail hanging out. Close the needle plate and you are ready to thread the top of the machine. The bottom thread will be picked up when you take your first stitch.
Removable bobbin cases: older and specialty machines
Some machines, especially older models and industrial or specialty machines, have a bobbin case that pulls straight out from the side of the machine. To access it, you usually turn a small latch or lever counterclockwise until the case comes free. The bobbin inserts into this case the same way — thread wound clockwise, sitting flat in the recess.
The tension lever on a removable case is often on the outside of the case itself, visible as soon as you remove it. Guide the thread under this lever from left to right, just as you would with a drop-in case. The thread should sit snugly in the slot. Some removable cases have a small spring that holds the thread in place; make sure the thread passes under that spring as well.
Reinsert the case by sliding it back into the machine at an angle, then turn the latch clockwise until it stops. Do not force it — the case should slide in smoothly. If it does not, remove it and check that the bobbin thread is not caught on the edge of the case.
What happens when the bottom thread is not threaded correctly
If the bobbin thread is not under the tension lever, you will see loose loops on the underside of your fabric instead of a tight, even stitch. The top thread may also look uneven because the machine cannot form a proper lock stitch. Some machines will also skip stitches or refuse to pick up the bottom thread at all.
The fix is straightforward: remove the bobbin case, rethread the bobbin thread under the tension lever, and try again. If you have already sewn a few stitches, raise the presser foot first — this opens the tension and makes it easier to remove the thread from the lever. You do not need to rewind the bobbin or start over; just guide the thread back under the lever and continue sewing.
Finding the tension lever if you cannot see it
On some machines, especially newer computerized models, the tension lever is not when ready obvious. It may be hidden under a small cover or located on the inside of the bobbin case rather than the outside. If you cannot find it after looking at the bobbin case itself, check your machine's manual — it will show you exactly where the lever is and how to thread around it.
If you do not have the manual, search for your machine's model number online followed by "bobbin threading" or "bobbin case diagram". Most manufacturers post PDF manuals on their websites. A photo or diagram will show you the exact path the thread should take. Do not guess — threading the wrong way can damage the tension spring inside the case.
Checking your work before you sew
Before you start sewing, hold the bobbin case in one hand and gently pull the bobbin thread with the other. The thread should not slide out easily. If it does, the thread is not under the tension lever and you need to rethread it. If it holds with a little resistance, you have done it correctly.
You can also do a test stitch on scrap fabric. Sew a few stitches and then look at the underside. If the bottom thread forms tight, even loops that match the top thread, your bobbin is threaded correctly. If you see loose loops or the thread looks slack, stop, raise the presser foot, and rethread the bobbin.
Frequently Asked Questions
Does the bobbin thread direction matter?
Yes. The bobbin should be wound so the thread comes off clockwise when you look at it from above. If you wind it counterclockwise by mistake, the thread will not sit properly under the tension lever and your stitches will be loose. Most machines have a small arrow or mark showing the correct winding direction.
What if the tension lever is broken or missing?
The bobbin case will not work without the tension lever — the thread needs that resistance to form a proper stitch. If the lever is bent or missing, the bobbin case itself may need to be replaced. Contact the machine's manufacturer or a local repair shop with your machine's model number to order a replacement case.
Can I use a bobbin from a different machine?
Not reliably. Bobbins come in different sizes and shapes — some are metal, some are plastic, and some fit only specific machines. Using the wrong bobbin can cause the thread to sit incorrectly under the tension lever or fall out during sewing. Always use the bobbin type your machine's manual specifies.
Why does my bobbin thread keep coming loose during sewing?
The most common cause is that the thread is not fully under the tension lever — it may be resting on top of it instead. Stop sewing, raise the presser foot, and check that the thread is actually underneath the lever, not just near it. If the thread is correctly positioned and still comes loose, the tension lever may be worn or damaged and need replacement.