Bobbins are small in size but a big part of sewing. When you’re in a pinch and need a bobbin urgently, you may wonder if a different size or style can fit in your sewing machines. 

Are Sewing Machine Bobbins Universal or Interchangeable?

Sewing machine bobbins are not interchangeable. While it may seem like a small part of the machine, a bobbin has to fit carefully into its slot. So, it has to match the weight and size of the recommended bobbin size and style for your machine. An off-balance bobbin can affect your stitchwork.

The importance of the bobbin size is its effect on the balance. A sewing machine is made specifically for a particular tension between its parts. 

That is why it’s not recommended to switch between metal and plastic bobbins even if they are the same type and size. A metal bobbin will be heavier and offset the balance. In the worst-case scenario, it can damage the sewing machine.

Are All Sewing Machine Bobbins the Same Size?

All sewing machine bobbins are not the same size. They come in different sizes as well as styles. They are also differentiated as metal or plastic bobbins, for which the material can affect the balance in tension. A particular machine only allows for one size.

What Are the Different Bobbin Sizes?

There are numerous variations in both size and style for bobbins. It can be confusing, so we have highlighted the most commonly used sizes:

L Class

The L Class bobbin is about 0.35 inches tall and has a diameter of about 0.91 inches. It’s similar to the size of a nickel. These are one of the most common bobbin sizes and frequently used in households or by hobby sewists doing embroidery.

M Class

The M Class bobbin is a bit taller and larger than the L Class bobbin. It reaches approximately 0.43 inches in height and has a diameter of about 1 inch.

The reason for this is that M Class bobbins are typically used in heavy work. For example, sewing leather, furniture covers, canvas, etc. The stitching is fast so the thread runs out quicker. 

A larger bobbin allows for a more wounded thread length. You would rarely see an M Class bobbin machine as a household sewing machine.

Class 15

The Class 15 bobbin has the same diameter as that of the L Class bobbin, like a nickel. Likewise, it’s frequently used in embroidery and household machines. The difference is in height. 

The Class 15 is about 0.125 inches taller. So, the Class 15 and the L Class are not interchangeable even though they have similar functions and sizes.

How Can You Tell the Difference Between Bobbins?

The easiest way to tell the difference is to check the labels. But not all bobbins come with labels.

As a sewist, there are a few bobbins you want to be able to differentiate just by looking and holding them. So, here are some pointers for that!

First off, we have the three most commonly used bobbins: M Class, L Class and, Class 15. 

It’s easy to tell the difference between the M style compared to the L style and Class 15. While the L and Class 15 bobbins have the same diameter of about 20.3 mm (close to the size of a nickel), the M style has a diameter of about 24.9 mm (close to the size of a quarter).

So, the M has a larger diameter. Furthermore, the M style typically comes in metal and Magna-quilt style, while both L and Class 15 come in plastic often, too.

Now, how do we differentiate between L and Class 15 if they have the same diameter? The answer is the width! Class 15 bobbins are about 11.7 mm wide and L Class bobbins are approximately 8.9 mm wide. 

As Class 15 bobbins are wider, you cannot use them in L Class machines. The opposite, using L Class in a Class 15 machine, is possible, though not recommended.

Next, we will talk about a few bobbins you might have seen: Singer #8228, Class 66, Class 15J, and the Bernina #0115367000.

The Singer #8228 has a long width (33.4 mm)  and a small diameter (9 mm). For this reason, it is the most distinctive bobbin you may come across. Mostly, we see it used on treadle machines by Singer.

The Class 66 and 15J are commonly mistaken as Class 15 bobbins due to their shared diameter (close to the size of a nickel). But it’s important to remember they are not interchangeable.

The Class 66 bobbin is slightly shorter and shaped like a dome on the sides. Newer ones typically come in plastic. 

The 15J is curved slightly. The difference is minimal to the eyes but it affects the sewing machine.

Finally, we have the Bernina #0115367000. It’s a bobbin used in Bernina models, especially the older ones. While it is the same diameter as Class 15 bobbins, you will be able to tell it’s a Bernina by the cross-hatch pattern inside the cylindrical-shaped metal.

Are All Class 15 Bobbins the Same?

There are two different Class 15 bobbins you may have heard of: the Class 15 and the Class 15J. They are not the same though they look almost identical. The Class 15J has slightly curved sides, while the Class 15 is flat on both ends like a coin.

Sometimes, you may be able to slot them in the same machine, even if they are not meant for that type of bobbin. However, it’s not a good idea to do that because your machine might jam up due to the difference in tension and shape.

Can You Use Plastic Bobbins Instead of Metal? 

You can use plastic bobbins of the same size instead of a metal one but you shouldn’t. Metal bobbins are heavier and require more tension. It may be too much for your plastic bobbin and cause it to break.

Moreover, the disorder in balance might jam your sewing machine. 

Are Metal or Plastic Bobbins Better?

Between metal and plastic bobbins, one is not better than the other when they are used in their rightful machines. Using metal bobbins for metal cases and plastic for plastic cases is the best choice.

Metal bobbins tend to last longer though they are more expensive. So, that is something to consider.

What Happens If You Use the Wrong Bobbin?

When you use the wrong size bobbin, your best-case scenario is that the stitchwork will not be as smooth. But more often than not, an ill-sized bobbin can damage or break the sewing machine. 

The sewing machine is made up of parts that work with a specific tension. So slight changes in shape, height, width, diameter, material, etc. can cause it to start malfunctioning.

For example, if you use a plastic bobbin instead of a metal one, even if they are the same size, you will face some problems. If you wrap the thread too tightly around it, the plastic bobbin will bulge. 

Since metal is heavier, it requires a higher tension. 

The higher tension can also make the plastic bobbin bulge. The height of the bobbin will increase, so the thread will catch. And your machine will jam while the bobbin may get stuck in the bobbin area of the machine. 

So, it’s best to use the bobbin style that the machine is built for.

How Do I Know What Size Bobbin to Use?

You can find the size of the bobbin you need to use by checking the owner’s manual. You may even ask the shop you got it from about the correct bobbin size. 

Before going to buy a bobbin, don’t just check the sewing machine’s brand. Note down the model you have, too. By finding the model number of your machine, you can search up the bobbin size or a dealer can find it for you. 

Can You Use a Sewing Machine Without a Bobbin?

You cannot use a sewing machine without a bobbin. The needle thread alone cannot work the machine. 

Two spools of thread are necessary, one for the top thread and one for the underside. 

However, some machines that sew without a bobbin do exist. They are not conventional sewing machines and are called chain stitch machines, overlockers, etc. The lock stitching we all know and love is only possible using a machine with a bobbin.

Bobbins are small but essential mechanisms of a sewing machine, so a slight difference can change the quality of your stitches drastically. It may even damage your machine. Using the recommended bobbin for your particular model is the safest choice.

Frequently Asked Questions:

Are Sewing Machine Needles Universal or Interchangeable?

What are The Parts of a Sewing Machine and Their Functions?

Can Sewing Machines Be Recycled?

Can Sewing Machines Do Overlocking?

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