There are many things we wish would last forever—first love, first warm day of spring, an ice cream cone on a hot summer day… and the bobbin thread on the machine. A never-ending bobbin: that would bring its inventor a pretty penny.
Bobbin thread has been the mainstay of the lock stitch since the sewing machine was invented. Both a multi-needle embroidery head and that first sewing machine rely on one bobbin to form the stitches needed to make the garment—and decorate it.
The case that holds the bobbin is extremely important as well. Just as the bobbin thread is an essential element of balanced stitching, the case itself serves as the lower tension unit for all the needles on that head.
Above is a bobbin case with its backlash spring removed; the image on right shows the bobbin and backlash. This metal plate is designed as a braking device to prevent back spinning of metal bobbins which have a tendency to spin and fly back when the machine stops or slows down.
But what about the thread that spools out from that case, catching the top thread in an endless dance? The choices are far wider than when I started stitching in this industry—and choice can be a good thing, if we know the basis for the decision.
I started embroidering goods in the days when bobbins were wound on metal reels while the machine was running. Machines are still made with a bobbin winder and metal bobbins come with your new machine. There are certainly times when having the ability to wind your own can be a blessing.
Many embroiderers choose to wind their own when producing a design that can be viewed from either side. It is important to choose a quality bobbin thread when winding your own bobbins. Any good, thin sewing thread will work for winding bobbins so choices are wide. Bobbin thread usually ranges from 80–120 in weight. If the thread is too weak, excess breakage may occur; if it is too thick, breakage and a poor quality embroidered design may be the result.
Monitor the winding of your bobbins as poor winding can cause thread jams, as well as poor quality and thread breakage. Consider marking the first yards with a washable marker as you wind so you know when the bobbin is running low. If you wind bobbins to match a spool or cone of thread, store them together in a sealable bag. To wind your own you must have metal bobbins and, if there is not a built-in bobbin winder on your machine, one can be purchased separately.
I remember being surprised and pleased when pre-wound bobbins were introduced. At first I thought it was an unneeded expense—surely it was less expensive to wind your own. But after trying them out, I was a fan. Nothing beat having an (almost) endless supply of thread that was (for the most part) wound with an even tension. Pre-wound bobbins come with no sides, plastic sides or cardboard sides. Side-less bobbins have more thread on them and last longer, but bobbins with sides invite easier tension control.
There are times when having a self-winding bobbin (right) is a blessing. Pre-wound bobbins, on the other hand, offer more even tension.
Bobbins are not always perfect. Sometimes they can be wound too tight or off-round. A bobbin must be symmetrical or it may rub against the bobbin case causing the thread to break or tension to loosen. An asymmetrical bobbin can cause specks of bobbin thread to appear on the surface of the design. The side-less version of the bobbin can have too much wax on it. While wax keeps the thread together on the bobbin core, it can build up under the adjustment spring and cause the tension to loosen.
If a bobbin is wound too loose, it can spin extra thread inside the case and cause problems. The bobbin should sit perfectly still while the hook moves around it.
Pre-wound bobbins are filled with cotton, nylon, spun polyester and filament polyester. If using a multi-head machine, a good way to test for the perfect bobbin is to try a different one on each head, using identical top threads, backings and fabrics. Those running single heads can try different bobbins, one at a time, testing with identical designs, top threads, fabrics and backing materials.
Cotton bobbin thread is not as strong as polyester and creates lint which can build up under the tension plate/leaf adjustment spring/adjustment arm on the bobbin case. This moves the plate away from the thread causing a loss of tension. The smooth texture of cotton bobbin thread allows for very fine tension adjustment. Cotton bobbins were once the only game in town and were used for delicate work—a task where they still shine. Cotton bobbin thread is an excellent choice for small lettering and delicate detailed stitching as it does not have the stretch of polyester and creates good, crisp stitching.
Nylon thread is made of 100 percent filament nylon, which means no lint. This bobbin is usually side-less and held together by a wax- or chalk-based coating which can create a buildup that rivals that of cotton’s lint. Clean the case and bobbin assembly well with denatured alcohol when using nylon bobbins. Nylon bobbin is very strong but is thin and slippery which can create tension challenges. Thinner thread means more thread on the bobbin, thus fewer bobbin changes. Nylon is a good choice when metallic or polyester is on deck for the top thread.
An example of a bobbin with cardboard sides (left) and one with no sides (right). Side-less bobbins have more thread on them, thus, last longer. Bobbins with sides allow for easier control. (All images courtesy the author)
Spun polyester is a popular bobbin thread similar to cotton in appearance and texture but stronger. Like cotton, it allows for fine tension adjustments. It is made from polyester staple which has been twisted together to form a filament. Because it is a staple twist (short fibers) there is lint formation, so the case must be cleaned more often when using spun polyester. It tends to break, so the machine needs to be running at its best.
Continuous filament polyester has strong tensile strength and is reliable. There are no yarn defects (slubs) where lint builds up and thickens thread. Besides strong, it is also thin, which means the range of tension adjustment is limited. It is made of continuous polyester filaments as opposed to spun polyester’s short staple fibers and so produces less lint than cotton or spun polyester. A bobbin with a magnetic core is available. It contains polyester thread and runs with a consistent sewing tension, allowing the bobbin thread to be used completely.
Pleading (for) a case
Keep the bobbin case clean, especially the slot through which the thread passes (formed by the leaf adjustment spring). Keep the case safe as dropping it can mean replacing it—a spare should be in your tool kit. When you are cleaning the case or changing the bobbin, do so over a safe surface. A hooped piece of backing makes a nice safety net.
Bobbin cases have a slim piece of metal inside called the check spring or backlash spring. This metal plate is designs as a breaking device to prevent back spinning of metal bobbins that have a tendency to spin and fly back when the machine stops or slows down.
When using side-less or paper-sided bobbins, the backlash spring can sometimes push the bobbin too close to the hook, especially if the bobbin swells, which can happen in damp weather. Many operators prefer to remove the brake when using pre-wound bobbins. Others say the bobbin runs too loose without the spring. Try both methods and see what works best.
The common denominator
I consider the embroiderer the backbone, the mainstay, of this industry. No machines, no bobbin thread… nothing runs without the operator. So give yourself a pat on the back and here’s a hug from me for a job well done—making the world more beautiful, one stitch at a time.
L Bobbin: 130 yards of thread (12,000–15,000 stitches)
M Bobbin: 269 yards of thread (25,000–30,000 stitches)
USAGE: 2.5 yards of bobbin thread per 1000 stitches