How Does a Sewing Machine Work?


Sewing machines revolutionized the clothing industry. Before that, everything had to be hand stitched. This is time-consuming and gets physically painful if you do it for long periods of time in one sitting. It is also impossible to standardize, which causes problems in terms of quality control, among other things.

A Revolutionary Concept

The sewing machine not only revolutionized the industry, but it is also a revolutionary concept. Machine stitching functions completely different from hand stitching. It was not obvious how to translate hand stitching to a machine environment.

Machine stitching works so fundamentally different from hand stitching that the inventor of the sewing machine reportedly couldn’t solve it until he slept on it. He had a not-safe-for-work dream that illustrated the idea of the motion and design of the type of modern machine sewing needle.

He woke up and realized he should move the eye of the needle from the back end of the shank to the tip. All attempts to get machine stitching to work using the existing design for hand sewing needles had been maddeningly ineffective.

Before we explain how the modern sewing machine works, let’s take a look at how hand sewing works. It was this process that somehow had to be completely re-envisioned and translated into a process that a machine could handle.

How Hand Sewing Works

With hand stitching, you need a sewing needle that has a pointy end, enough shank to hold it between your finger and thumb and an eye (or hole) on the other end for the thread.

You use a single thread and laboriously go from front to back. The needle gets pushed through the material and pulled out the other side again and again.

Threading the needle can be a big nuisance and has to be done fairly frequently because you cannot realistically use thread that is much longer than your arm. Very long threads are too unwieldy. They tangle up too easily, causing the work to become botched.

Trying to use very long threads frequently means winding up with a knot that cannot pass through the eye of the needle anymore. At that point, the thread has to be cut, the needle may need to be re-threaded and the thread knotted again to serve as an anchor.

Beginning a seam is a production. Trying to anchor the beginning of the thread can be one of the hardest parts of the process. If it isn’t properly anchored, it can pull through completely or readily come unraveled.

It’s also common to get poked accidentally with the needle. Thimbles are intended to help protect fingertips from the abuses of hand sewing. With heavy material, it can require physical force to push the needle through. A thimble can allow the seamstress to exert this force with less pain and suffering.

How Machine Sewing Works

One of the best things about moving from hand sewing to machine sewing is that there are far fewer opportunities to get hurt like that. This is especially true when you compare it in terms of how much more sewing can happen on a machine in the same amount of time. Much more work gets done in the same amount of time, with far fewer poked fingers.

In contrast to hand sewing, the mechanical process of machine stitching involves two sets of thread, one from the top and one from the bottom. It is much more efficient because you can use very, very long threads. They just have to be carefully wound around delivery mechanisms, a spool and a bobbin.

This means far more seams are being made for the time involved. A great deal less time is spent on details like periodically re-threading the needle.

The spool is the tiny barrel that thread comes on when it is purchased. They were originally wooden, but are typically plastic these days. The bobbin is similar to the spool but smaller and usually made of metal. In most cases, the seamstress fills the bobbin with thread from the spool so that they are an exact match in color.

But if you have a sewing machine, you can get a better idea of how machine stitching actually works by using two different colors of thread, one on the spool and the other on the bobbin. Ideally, they should both stand out starkly against the fabric you choose to use to create a small sample for your own edification.

If you are trying to understand how machine sewing actually works, this is an excellent exercise to try at least once. It can also be fun.

Here is a static illustration of the machine lock stitch. It uses different colors for the top thread and the bottom thread to help make things clear.

The Actual Mechanism

There is also this terrific GIF that not only uses two different colors of thread to help you distinguish them, it also uses live action to illustrate the machine stitching process. Please note that the process is vastly faster in reality. This illustration is very much slower than a real sewing machine.

The bobbin is actually the metal circular part in the center. The bobbin is kind of like a very small spool, but specialized because it needs to be more a part of the machine than the spool. The spool can kind of loosely sit on top and have thread unwind from it. It doesn’t have to be so closely fitted to the machine. But the bobbin gets inserted into the machine mechanism, so it needs to meet much stricter requirements.

The machine mechanism that helps hook the two threads together is the shuttle. The above GIF shows a simplified cut-away of these various parts. In reality, you wouldn’t be able to see the green thread wrapped around the bobbin. The shuttle is the outer partial circle with a hooked end that grabs the yellow thread off of the needle in order to begin the looping process.

In contrast, this is what an actual shuttle looks like:

The above photo also includes a close up of the foot and the feed mechanism. The foot helps hold the material flat and allows for controlled, even stitching. The feed mechanism helps pull the fabric forward at an even pace. The seamstress does feed material through by hand and their actions matter, but these mechanisms set a higher standard for sameness than most people can achieve by hand.

If you are going to learn to sew, you need to pay very close attention to learning how to properly wind and thread the bobbin, as well as properly thread the machine. For people new to sewing, the complex process of threading the machine is a very common source of frustrating experiences. The machine cannot successfully create stitching if anything goes wrong on the spool, the bobbin or the threading.

When you wind the bobbin with new thread, it needs to be done very evenly. In order for the machine to run fast without the thread knotting up and breaking, the thread needs to be able to ream off of the bobbin and the spool simultaneously at high speed without tangling or catching.

Improperly winding the bobbin can create knots that catch on the machine parts, causing the thread to break. Broken threads can get caught in the machine, causing more problems. If you ever break a thread, you need to check to find any small bits of thread left behind somewhere in the machine and remove them before you try again.

A good seamstress learns to properly wind the bobbin and thread the machine. This is a critical step in the process and happens before any sewing can happen.

A very important part of winding the bobbin properly is getting it started properly. Some people hand wind thread around the central shaft to get started. This is the wrong way to start the process and can lead to problems down the road. It can promote tangles and broken thread.

Note that bobbins come with one or more holes in the ends. Put the thread through there and hold it. It’s much easier than hand winding the thread to start and it helps the thread to go on evenly so it will play nice with the rest of the machining.

Here is a good tutorial showing a bobbin being started properly:

Powering The Mechanism

The critical part of a sewing machine is the above interaction between the top thread and bottom thread. This is handled by the needle and shuttle interacting with two sets of thread, one drawn from a spool and the other drawn from the bobbin.

The rest of the machine houses the motors that drive all of this. They just make it possible to go very fast, but the needle, foot, feeder, shuttle, and bobbin are where the action happens. That’s where the rubber meets the road. Or, you know, where the stitching meets the fabric.

Although the earliest sewing machines were much faster than hand sewing, they were still far slower than machines are today. They didn’t have the elaborate motors that are now standard. In fact, they weren’t electrical at all. Because of this, the bodies of very old sewing machines are much smaller than is the norm for modern sewing machines.

So, although many people may think of sewing machines as kind of like electrical appliances, they are really mechanical devices. As it says right on the label, they are machines.

Well before electricity was the norm, they could be run on human energy, though more slowly than they can be run on electricity today. This is a picture of an old-fashioned Singer sewing machine with a foot pedal for powering it:

That would be quite the workout. You would have to keep moving the foot peddle to get it run. It would be a little like running on a treadmill while seated and trying to sew at the same time. Does that make you tired just thinking about it?

Stitch Variety

When someone sews by hand, they need to learn a variety of different stitch types. Different stitches serve different purposes. Protection Status