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What Is a Bobbin? [Complete Guide]

Like the gears inside a clock, the inner workings of a sewing machine may seem mysterious or complicated at first glance. What is a bobbin, and do you need this part of your sewing machine? The answer is yes, but the good news is that you can easily learn how to use a sewing machine bobbin!

The bobbin in a sewing machine supplies the lower thread that locks each stitch into place on the underside of the fabric as the machine sews. The bobbin has a cylindrical or reel-like shape. Most sewing machines feature a bobbin winding device for filling the empty bobbin with thread before sewing.

In this article, you will learn what a bobbin is and how it works. You will discover several different styles of bobbins and learn which one will work best for you. Finally, you will discover how to troubleshoot common bobbin issues as you sew.

What Is a Bobbin

What is a Bobbin on a Sewing Machine?

A bobbin is a spool or reel designed to hold thread, yarn, or other material. In sewing machines, a bobbin serves as a secondary thread source for the machine. Plenty of other machines use bobbins, including knitting machines and other industrial machines.

Sewing machine bobbins today look like small, flattened cylinders, usually less than one inch in diameter. Bobbins can come in plastic, metal, or even wooden form, though most sewing machines use metal bobbins.

Bobbin on Sewing MachineWhy is a bobbin called a bobbin? The word comes from the French term bobine, which means a “small sewing instrument.” It does not mean that a bobbin bobs up and down as the machine sews!

Credit for the invention of the earliest sewing machine bobbin goes to a man named Allan Wilson. Way back in 1850, Wilson patented a design for a “reciprocating shuttle machine” that had a pointy shuttle that acted very much like a bobbin in a sewing machine today. This shuttle provided the crucial second thread source for the machine.

The waters get considerably muddied after this, and it gets much harder to trace the history of the bobbin. Dozens of sewing machine inventors and companies launched a period known as the “Sewing Machine Wars,” filing patents rapid-fire at each other to try to claim new inventions.

Some of these inventors include famous names like Elias Howe and Isaac Singer. The Singer company eventually took credit for the Class 15 style bobbin, which remained the most popular model for decades.

One interesting invention of note, though, is the invention of the modern, round bobbin. The credit for this goes to Yosaku Ose, the founder of Japan’s Janome sewing machine company. In 1921, Ose upgraded the bobbin from the longer shuttle style to the current round shape we use today. The term “Janome” means snake-eye, a reference to the famous round bobbin!

Believe it or not, the invention of the sewing machine bobbin is what sparked the creation of sewing machines as we know them today. This is because the bobbin gives the sewing machine its two-thread system.

What Is a Bobbin Used For?

What Is a Bobbin Used For

The purpose of the bobbin in a sewing machine is to provide a second thread that allows the machine to create a lockstitch. The bobbin holds the lower thread and the spool pin holds the upper thread on a sewing machine. The invention of the lockstitch model launched what we think of as the sewing machine.

A lockstitch uses two threads to “lock” the thread onto the top and bottom of a layer of fabric, creating stitches.

To understand how a lockstitch works, first you need to picture the way a hand-sewn stitch works. In the days before sewing machines, people sewed with a needle and thread. Every hand stitched required a tailor to push the needle through the layers of fabric.

The thread, caught in the eye of the needle, would slide through the fabric as well. The tailor would now hold the needle and the length of thread on the reverse side of the layers of fabric.

He or she would move the needle over a small space from that thread, insert the tip of the needle back into the fabric from the back, and pull it back through again. This would leave a small section of thread lodged on the back of the fabric, creating a stitch.

On a sewing machine, the needle and thread cannot go all the way through the fabric and then come back up from the reverse of the fabric because the machine holds the needle in a stationary position.

To get around this difficulty, the machine makes a lockstitch. In a lockstitch, the needle still pushes a loop of the upper thread down through the cloth. While this happens, the case around the bobbin spins, carrying the lower thread.

The shuttle hook on the bobbin casing catches the upper thread and loops the lower thread around it. In this way, the bobbin thread grabs the needle thread and holds it to the underside of the fabric. This creates stitches!

Where exactly is the bobbin in a sewing machine? If you have not used a sewing machine before, you might think of the bobbin as “one of those inside parts,” because you cannot see the bobbin when you first look at the outside of the machine. In fact, your sewing machine could house the bobbin in two different places.

Many sewing machines have a front-loading bobbin. In this case, you will find the bobbin behind a hatch that opens up in the base of the machine right beneath the needle. The bobbin will slot into the casing standing up on one side of the wheel.

The other popular placement for bobbins is called a top-loading bobbin. In this case, a small slide will cover the bobbin right in front of the needle plate. You will slot the bobbin in flat-side down in this type of machine.

Why Do Sewing Machines Have Bobbins?

Why Do Sewing Machines Have Bobbins

Sewing machines have bobbins because they require two thread sources to create a lockstitch. Some machines use larger bobbins, but most use a small, cylindrical shape that can easily slot into the mechanism placed beneath the needle.

This way, the machine can pull up for the lower thread and pull down for the upper thread, all in one smooth stitch!

You may wonder why sewing machines do not simply use two spools of thread instead of the tiny bobbin. After all, you have to pause to refill the bobbin repeatedly as you sew!

The answer is that small, so-important shuttle hook on the outside of the bobbin casing. This hook catches the upper thread and is what allows the upper and lower thread to lock together.

The hook has to quickly circle the shape of the bobbin case for each stitch. This means that a smaller bobbin works better for a smooth sewing process.

Different Types of Sewing Machine Bobbins

Types of Sewing Machine Bobbins

Different types of bobbins include the Class 15, the M-style, and the L-style, among others.

Today, the most commonly used style of bobbins is the L-style. This version has a .8” diameter, meaning that it has the size of a nickel. It only offers a .35” width, though, meaning that it does not hold a lot of thread.

The Class 15, first invented by Singer in the early 1900s, remains another popular choice for modern sewing machine bobbins today. This bobbin has a .835” diameter, making it just a fraction larger than the L-style. The bigger difference is that it also has a .465” width, meaning that it can hold much more thread.

M-style bobbins typically get used in longarm quilting machines or industrial machines. They are much bigger, measuring in with a .98” diameter and a .42” width.

Quilting machines, in particular, often use larger bobbins. These machines sew so fast, forming so many stitches per minute, that they need a bigger secondary thread source to draw from.

Some sewing machines come with specialty bobbins designed just for that machine. You see this a lot in antique machines, especially.

A few of these lesser-known bobbin types include the G-style, J-style, U-style, Z-style, and Class 66 bobbins.

Another thing to note about different bobbin types is that bobbins can be made out of metal or plastic.

Do all bobbins work in all sewing machines? No! You should only use the type of bobbin that comes with your machine.

Finally, you can also find one big difference in bobbin machine cases. Many beginner and intermediary level sewing machines use an oscillating shuttle hook.

In this model, the shuttle hook goes halfway around the circle of the bobbin case to catch the upper thread, but then it falls back to its beginning position. Basically, it forms a half circle as it moves.

There is nothing wrong with this model–it has worked for over 150 years! But it can cause more vibration and may not operate quite as smoothly as the second type of shuttle mechanism.

Most professional and all industrial sewing machines use a model called the rotary model. In this case, the shuttle hook makes a full circle around the bobbin case. It moves quickly and smoothly and makes less noise than an oscillating shuttle hook.

Do All Sewing Machines Have Bobbins?

All sewing machines have bobbins, including quilting machines and embroidery machines. The only exception to this rule is a special type of sewing machine called sergers or overlock machines.

This is because sergers do not use a lockstitch. Instead, they create an overlock stitch that loops three or more threads together in a complex braid around the cut edge of the fabric as the machine sews.

All domestic sewing machines use bobbins. That said, the size and type of bobbin can vary from one sewing machine model to another. You should always make sure you use the correct type of bobbin in your machine!

Are Sewing Machine Bobbins Universal?

Are Sewing Machine Bobbins Universal

Sewing machine bobbins are not universal because there is no one-size-fits-all bobbin that you can plug into all sewing machines. That said, you can find three standardized classes of bobbin types, and most sewing machines use one of these three types.

As you saw earlier in the article, these types are the L-style, M-style, and Class 15 bobbins.

Your sewing machine manual will tell you which style to use. If you look at the sizing chart below, you quickly understand why you cannot put an M-style bobbin into the case meant for an L-style bobbin!

Bobbin Sizes Chart

This chart gives you an overview of the size of the most commonly used types of bobbins.

Type of Bobbin Diameter Width
L-style .8” .35”
M-style .98” .42”
Class 15 .835” .465”
Class 66 .807” .429”

Can You Sew Without a Bobbin?

You cannot sew without a bobbin on a regular sewing machine. Every machine that uses a basic lockstitch structure, including quilting and embroidery machines, requires the bobbin to provide a lower thread. The only exception is sergers, which use a different stitching structure and do not need a lower thread.

Really, the only way to avoid using a bobbin is to sew by hand!

It’s actually kind of fascinating that the tiny bobbin, measuring less than one inch in diameter, makes such a huge difference in the operation of a sewing machine.

Bobbin vs Spool: What is the Difference?

The main difference between a spool and a bobbin in a sewing machine is that the bobbin goes beneath the needle, and the spool goes over the needle. The spool thread follows the upper thread path to wind through the tension discs, over the thread take-up lever, and finally down to the eye of the needle. The bobbin thread slots into the bobbin case.

Technically, a bobbin is a small spool. But in sewing machine terms, you typically think of the spool as the spool of thread that goes on the spool pin.

What is a Bobbin Winder?

What is a Bobbin Winder

A bobbin winder is a mechanism that allows you to fill an empty bobbin with thread. Most sewing machines feature this handy device because you generally want to use the same color of thread on the bobbin and spool as you sew. If you use two different threads, you will see the contrast in color in the stitches and your sewing will not invisibly blend into the fabric.

Because of this, most sewing projects begin by winding an empty bobbin with thread off the spool.

The bobbin winding mechanism may look a little different from one sewing machine to another. You can always find a guide to this process in the owner’s manual that comes with your machine. But the basic steps always look pretty similar.

  1. Start by sliding the spool of thread onto the spool pin and placing the spool cap onto the end of the pin. (If your sewing machine uses a vertical spool pin, you might place a felt circle on the spool pin and then slide the spool into place instead).
  2. Push the empty bobbin onto the bobbin winder pin, typically located on the top of the machine.
  3. Tug on the end of the thread to free about twelve inches.
  4. Follow the thread guides on the top of the machine casing. For most bobbin winders, you wrap the thread once around a stationary screw close to the spool of thread. Then stretch the thread across the machine to the empty bobbin.
  5. Wrap the thread around the bobbin twice, and hold the tail in your hand.
  6. Gently push the bobbin and the pin to the side until it bumps into the small stopper to the right.
  7. Turn on the sewing machine and push down the foot pedal to run the bobbin winder. Let go of the thread as soon as the machine tugs on it.

Troubleshooting Bobbin Problems

Learning how to troubleshoot a few common bobbin problems will simplify your sewing time greatly. When you think about it, the bobbin supplies half of the thread for every sewing project, meaning that the bobbin mechanism holds responsibility for 50% of every sewing project!

Fortunately, the bobbin does not typically cause a lot of trouble. Check out these common issues and solutions:

  • You notice that stitches do not form on the cloth as you sew or that the upper thread punches through and seems to form stitches but does not catch on the lower thread. This happens mostly because you have run out of thread on the bobbin! Simply rewind the bobbin and start sewing again.
  • If you hear loud vibrations or grating noises coming from the bobbin mechanism, stop sewing at once. The bobbin may have dents that have misshapen it and kept it from turning. Replace it with a new one, making sure you choose the appropriate model for your sewing machine.
  • If your machine jams up with a bird’s nest of thread beneath the fabric as you sew, the problem is more likely the upper thread than the lower thread. However, as part of rethreading the machine to resolve this problem, you should take out the bobbin, slot it into its case again, and make sure the thread unspools smoothly.
  • If you notice that the lower thread has created loose stitches to form on the fabric, you may need to rewind the bobbin. An unevenly wound bobbin can cause uneven stitches in some cases.
  • Another common cause for a skipped or uneven lower thread while sewing is that you need to clean around your bobbin! Old lint and grease can cause the bobbin case and that essential hook to jam or move slowly.

As a pro tip, you should also consider loading two or three bobbins with the same color of thread before you start a big project. That way, when you run out of bobbin thread, you can just slot a new one in without interrupting the whole project to reset your machine as a bobbin winder.

Where to Buy Bobbins

You can buy bobbins anywhere that sells sewing supplies, from Walmart to Joann Fabric to Amazon. If you have a unique machine, such as an antique or a specialized quilting machine, you may need to visit online sewing parts stores instead to find the right bobbin for your machine.

Make sure you check your sewing machine manual to find out what size of bobbin you should buy before you shop. If you do not have a manual, you can find the model number on your machine and do an internet search to find out what kind of bobbin it takes. Please do not try to shove any old bobbin into your machine–this could damage it badly!

As you browse the notions aisle of a sewing store, you may notice cases of pre-loaded bobbins next to the empty bobbins on the shelf. Generally speaking, you want to avoid these. First, you now know that bobbins do not have universal sizing, meaning that these preloaded versions may not fit your machine.

Second, even if you find a color of thread that matches your project, it may not have the same weight or even contain the same material as the thread you picked for the upper thread!

Finally, pre-wound bobbins may not use the same tension as your bobbin-winding mechanism. This could throw off the rhythm of your machine as it has to pull harder to get the thread off of the too-tightly-wound bobbin.

It’s always a better idea to wind your own bobbins so that the upper and lower thread will match exactly as you sew.


A bobbin is a small wheel-shaped cylinder that provides a second source of thread for your sewing machine. It holds the lower thread, while the spool of thread on the spool pin holds the upper thread. Your machine draws on both thread sources as it sews, creating a lock stitch that hotels the thread to both sides of a piece of fabric to form stitches.

Bobbins come in various shapes and sizes, including the popular L-style and Class 15 types. You should always use only the type of bobbin that comes with your sewing machine.

Do you know what type of bobbin your machine uses? Have you ever ordered new ones for your machine? Leave a comment below to let us know!