The bobbin is that small spool (plastic or metal) that you wind with thread for the lower thread supply on a sewing machine. Your sewing machine uses it as the thread on the underside of the fabric for making the lockstitch that joins a seam. It is when the bobbin thread and the top thread lock in the center that you get a stitch. If everything is alright as it should be, the top thread and the bobbin thread lock perfectly between the layers of fabric without any loop, thread bunches, breaks on top or bottom, and no puckers on the seam line.Over all perfect stitching.
So a bobbin holds a very important part in your sewing life. But then you may already know this, at least by the amount of time you use to wind the many bobbins before any project. In fact, experienced sewists recommend that you should pre-wind 3 to 5 bobbins before a project so that you do not run out of bobbin thread in the middle of the project.
Or else, you can buy pre-wound bobbins – they are very convenient if you want to save time. Usually they are in white and black. It will be wound with about 80 yards/74 meters of thread.
Bobbins may be made of metal or plastic. When you buy your machine you get some free bobbins. But if you want the convenience of uninterrupted stitching, you will be buying some extra bobbins.
Ensure that the bobbins you buy will be a proper fit for the machine you have. If you have a machine that uses plastic bobbins, do not go out and buy metal ones or ones too large or too small – just becuase they are available. The bobbin you buy should be a perfect fit for the bobbin case in your machine. But usually bobbins between brands/sewing machines are interchangeable.
All sewing machines come with a bobbin case to hold the bobbin properly. This case may be detachable or it may be fixed. Another important element in the bobbin story is a winder – this is a mechanism in the sewing machine which helps you wind thread on the bobbin.
A stitch is started in your machine this way – You thread the machine properly, insert the wound bobbin, then pull the needle thread in one hand and then turn the handwheel towards you with the other hand – the needle will go down and grab the bobbin thread and return back with the bobbin thread. Pull it up and leave it hanging to the back of the machine before you start sewing. You can learn more about how to get started in sewing in the post – Simple guide to start sewing with a sewing machine
Thread used on the bobbin
Most people use the same thread for the top and bobbin. You will definitely want to do this if the reverse side is likely to show. If the back layer fabric is a different color use this color on the bobbin. Some use a grey thread on the bobbin for a lot of their sewing.
A lighter weight thread should be used on the bobbin for decorative stitching for eg: satin stitches for applique. If you buy bobbin thread you will find that it is thinner than regular top thread and is only suitable for embroidery projects. It maybe not be strong enough for seam sewing.
For decorative stitching called bobbin work, you will be using a heavy thread on the bobbin. You can read more about Bobbin work here.
The appearance of bobbin thread
The bobbin has to be properly inserted as well as positioned for the machine to work properly. Bobbin thread usually forms the same stitching line as the top thread. But this also depends on the thread you use as well as the sewing machine thread tension. When you are using a double-needle on the machine, the bobbin thread forms a zig-zag on the back of the fabric.
If you are sewing a straight stitch, and you are sewing with two colored thread – ie different colored thread on the top spool and the bobbin, ensure that the bobbin thread is not showing up on the top of the fabric and the top thread is not showing on the bottom of the fabric. When the bobbin thread shows on top of the seam, it means that the upper thread tension is tighter than that of the bobbin thread.
Winding a bobbin
Winding the bobbin can be different for different sewing machines. Basic instructions on winding a bobbin will be illustrated in your sewing machine manual.
Usually, this is how it goes – First ensure that the needle is in an up position. Take out the thread from the needle. Keep the bobbin spool on the bobbin winder. Engage the bobbin winder (or in some machine, this happens automatically). Run the thread through the sequence specified in your sewing machine manual. Start winding the bobbin, slowly and evenly
Ensure that you do not run away with the speed. Wind slowly so that the thread does not stretch too much. If the thread is stretched, it may cause puckered seams.
What to do if the Bobbin doesnot wind
Ensure that the bobbin winder is engaged. If it is not properly engaged, due to thread knots, switch not working, etc. the needle would work and you would not be able to wind the bobbin. See that the bobbin is sitting nicely on the winder, not on top of a thread bunch.
How to change the tension of the sewing machine through bobbin
For regular sewing, It is advisable not to change the tension on the bobbin case. And anyway, on most modern home sewing machines you cannot do anything to the bobbin tension.
In some machines the bobbin is placed on the front on the machine (called the drop in bobbin case) ; and in some machines the bobbin case is placed vertically under the needle plate. This usually has a seperate detachable metal bobbinc case.
If you have a machine with a non-removable bobbin case, you will have to make do with not touching the bobbin area for any tension adjustments. You will have to tighten or loosen the top tension for all your sewing machine manipulations.
In such cases, whatever tension adjustments you want to make, make it on the upper thread. The tension of the bobbin is usually kept a little higher than that of the upper thread. If the tension of the bobbin is too low, or that of the top thread is too high, the bobbin thread can be seen on the top of the fabric and this is not very attractive. There is a fine line of tension adjustment that you should perfect for achieving a good stitch, that will join fabrics without broken stitches, puckered seam, and frustrations. You can learn more about sewing machine tension adjustments here.
For decorative stitching, you will want to loosen the top thread tension a lot less than the bobbin thread to get the zig-zag stitch to look good.
On removable metal bobbin cases, you can increase or decrease the bobbin thread tension by adjusting the screw on the side of the case. Usually, this is done when sewing with elastic thread or for decorative stitches. The screw is tightened to increase the bobbin tension and the screw is loosened to decrease the bobbin thread tension. Turn left to decrease tension, to the right to tighten the tension. If there are two screws, adjust the screw near the spring on the case.
Remember that too much of these adjustments can damage a good bobbin case- buy a second bobbin case and use the adjustments on one rather than on the only one you have.
Bobbin case issues – instant solutions
If lint collects around and inside the bobbin case, it can cause a lot of problems in your sewing – clean everything thoroughly around the bobbin case with a soft brush. This is especially if you use cotton thread on the bobbin. Cotton thread can cause a lot of lint. You can use spun polyester thread to avoid lint.
Sometimes dust and lint are not the only culprits. Broken needles, small pieces of fabrics, other things can get stuck inside the bobbin case and cause the whole machine to stop working.
Do not use bobbin which is chipped.
Make sure that the bobbin is exactly the type that your sewing machine manual recommends and that your bobbin is correctly inserted. You should also ensure that the bobbin is threaded properly.
If stitches are not as it should be, ensure that the bobbin has been wound properly. Make sure that the bobbin doesnot appear to be knotted anywhere. When winding the bobbin, go at an even pace – running the machine too fast can cause the bobbin thread to have too much tension and cause puckering on the seam.