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Understanding Bobbins: What Every Sewist Should Know

Did you know there are over 60 different bobbin styles available? Some are dramatically different, while others are so similar it’s difficult to see any difference at all. Let’s take a closer look.

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About 95% of household sewing machines use the following 3 bobbins…

The Class 15 (A Style) Bobbin:

The Class 15 is about the size of an American nickel. Its diameter measures approximately 20.3 mm and has a width of approximately 11.7 mm. This bobbin has two flat sides and is available in both plastic and metal.

The L Style Bobbin:

The L Style is about the size of an American nickel. Its diameter measures approximately 20.3 mm and has a width of approximately 8.9 mm. This bobbin has two flat sides and is available in aluminum, plastic, and as a Magna-glide core.

It’s worth noting that the L Style bobbins are the same diameter as the Class 15 bobbins. As such, you can use L Style bobbins in a sewing machine that uses Class 15 bobbins. However, a Class 15 bobbin is too wide to fit in a machine that uses L Style bobbins.

The M Style Bobbin:

The M Style is about the size of an American quarter. Its diameter measures approximately 24.9 mm and has a width of approximately 10.7 mm. This bobbin has two flat sides and is available in metal, and as a Magna-glide core.

Below are more bobbins you may have come across while sewing, as well as a few that are just cool to know. We’ll call these our “honorable mentions”…

The Singer 163131 Bobbin:

The Singer 163131 is about the size of an American quarter. Its diameter measures approximately 27.3 mm and has a width of approximately 6.7 mm. This bobbin is only available in plastic.

This bobbin was featured in the old Singer Touch and Sews. The 3 unique lines indicate thread yardage. The inner circle equals 2 yards, the middle circle equals 10 yards, and the outer circle equals 20 yards (a full bobbin). The coolest feature is that it can be disassembled to quickly remove any unwanted thread.

The Singer 8228 Bobbin:

The Singer 8228 is probably my favorite bobbin because it looks so cool. Its diameter measures approximately 9 mm and has a width of approximately 33.4 mm. This bobbin is only available in metal.

This bobbin is used in the old Singer treadle machines and fits inside a bullet-shaped bobbin case. Pretty neat!

The Class 15J Bobbin:

The Class 15J is about the size of an American nickel. Its diameter measures approximately 20.4 mm and has a width of approximately 11.3 mm. This bobbin is only available in  plastic.

This bobbin looks very similar to the Class 15 bobbin, however, there is a slight curve to the sides. Even though the curve is barely visible, it’s still significant enough to affect performance.  As such, a Class 15J should not be used in a Class 15 machine.

The Class 66 Bobbin:

The Class 66 is about the size of an American nickel. Its diameter measures approximately 20.5 mm and has a width of approximately 10.9 mm. This bobbin is available in metal and plastic.

This bobbin is significantly curved on the sides and fits the black Apollo bobbin cases. Again, although this bobbin appears to be the same size as the Class 15 bobbins, it should not be used in a Class 15 machine.

The Bernina 0115367000 Bobbin:

The Bernina 0115367000 is about the size of an American nickel. Its diameter measures approximately 20.5 mm and has a width of approximately 10.6 mm. This bobbin is only available in metal.

This bobbin is common in the older Bernina machines and has a distinctive cross-hatch pattern etched into the barrel. Although this is the most common Bernina bobbin, there are many other Bernina bobbin styles available.

The Juki 270010 Bobbin:

The Juki 270010 is about the size of an American nickel. Its diameter measures approximately 20.8 mm and has a width of approximately 8.7 mm. This bobbin is only available in metal.

These are the most commonly used Juki bobbins and look very similar to the L Style bobbins, however, you should not use  L Style bobbins in place of the Juki 270010.

The Viking Specific 4125615-45 Bobbin:

The Viking Specific 4125615-45 is about the size of an American nickel. Its diameter measures approximately 20.9 mm and has a width of approximately 10.4 mm. This bobbin is available in plastic only.

This a Husqvarna Viking exclusive bobbin that fits most newer machines. It specifically fits all Husqvarna Viking machines in groups 5, 6, and 7.

Now that you know more about the different bobbin styles, let’s learn about general bobbin composition and care…

Metal Bobbins:

Metal bobbins are composed of treated steel. These are the most common bobbins available and are often preferred over plastic and aluminum.

Plastic Bobbins:

Plastic bobbins are becoming more popular, as they are durable and inexpensive. Despite popular belief, plastic bobbins generally perform just as well as metal bobbins.

Aluminum Bobbins:

Due to the lighter weight of aluminum, these bobbins spin faster than metal and plastic bobbins, hence the term, “Quick Wind”. Many believe aluminum bobbins perform better than metal and plastic bobbins, however, it’s worth noting that aluminum bobbins are more easily scratched and damaged.

Fil-Tec Magna-Glide Cores:

Fil-Tec’s Magna-glide pre-wound bobbins are essentially just a bobbin barrel wound with thread. The magnetic core prevents backlash, creating consistent stitches without needing a backlash spring. Once empty, the core can be disposed or recycled.

Bobbin and Bobbin Case Care:

Most importantly, you must take good care of both your bobbin and your bobbin case. The condition of your bobbin and your bobbin case dramatically affects your stitch formation. It’s important to intermittently inspect both your bobbin and your bobbin case to ensure no scratches or burrs have developed. Even the slightest nick will cause skipped stitches and thread nests. We recommend gently gliding your finger along all sides of your bobbin and bobbin case to check for inconsistencies. If you do discover a small scratch or burr, you should replace you bobbin immediately. A small scratch on your bobbin case can usually be gently buffed out with fine sandpaper. However, serious damage requires buying a whole new bobbin case.

Also, it’s best practice to use the same bobbin type as the bobbin that came with your machine. For instance, if your machine came with a plastic bobbin, you’ll have the best performance with plastic bobbins, even if metal ones are available.

If you’re not sure which bobbin your machine uses, give us a call or email us. We’re happy to help!