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How does a sewing machine work

What am I going to learn?

In this section, you’re gonna learn what are the pieces composing your sewing machine, what role they play and how do they work. This is going to be helpful for you to better understand the main features of sewing machines in order to take full control over your faithful (but sometimes rebel) ally!


The basic working principle of sewing machines is very simple: two threads, one needle, up and down, stitch formed. That’s it. However, when we look at sewing machines they seem much more complicated! They are made of many pieces which synchronously work together to form stitches. In this post you’ll learn what those pieces are and what role they play in our sewing projects.

There’s also a distinction between mechanical and electronic sewing machines. While the basic components are the same, electronic machines are more sofisticated as there’s something inside similar to a computer and programmed to do the stiches and the other functions.

Below you find an overview of all the parts that build up all sewing machines. In the second part of the guide, you’ll also see a few features only available on electronic sewing machines which, I have to admit, make the sewist’s life away easier.

Read on and find out more about your faithfull sewing ally. If you have any question, just drop a line in the comment section below and I’ll be happy to reply!

Ciao ciao!

Mechanical sewing machines

Bobbin winding guide
This guide is used to create thread tension while winding the bobbin. Some machines have a separate guide for winding the bobbin, others share the same guide both for threading and bobbin winding.

Bobbin winder
This is where you have to put your empty bobbin to wind it. Sometimes it has a small stopper on one side that prevents the bobbin from being wound more than a certain amount. In some machines there is also a thread holder/cutter at the base of the bobbin winder to hold the one end of thread that you have to initially wind manually.

Bobbin and bobbin case
The bobbin is a small spool that holds the lower thread and is located below the presser foot. Some machines have front-loading bobbins, some others have top-loading ones. In order for the machine to work properly the bobbin needs to be correctly placed into the bobbin holder. Most machines have visual instructions printed on top of the bobbin cover plate indicating how to insert the bobbin and the running direction of the thread.

Spool holder
This is where the spool with the top thread goes. Sometimes it is vertical, sometimes horizontal with a plastic spool holder preventing the spool from flying around while sewing. Some machines have 2 separate spool holders, as they support sewing with a twin needle, which requires two separate threads. This is actually handy also for winding the bobbin, as you don’t have to unthread your machine (provided you have a second matching spool). The second spool holder is usually detachable so that it doesn’t get on you way when you don’t need it.

Upper thread tension dial
This dial is gonna be one of your best allies! It allows to adjust the tension of the upper thread. There is usually a range of values that are optimal for most fabrics, but in some cases (i.e. for thicker or stiffer fabrics or specific types of stitches) you’re gonna need to set it to a suitable value. How do you know when you need to change your tension? Well, the ideal straight stitch has thread loops holding upper and lower thread together that meet exactly in the middle of the fabric (or between the two layers you’re sewing). If you had different colours for your upper and lower thread you would see pretty clearly when the tension is wrong: you would either see the lower thread showing at the top (tension too high) or the upper thread showing at the bottom (tension too low). When your stitches are evenly balanced, then you got the perfect thread tension! Have a look at your instruction manual to see what is the optimal setting for your machine and how to recognise wrong tension settings. They also usually include for each stitch type the corresponding optimal tension range.

Thread guides
Thread guides are used to give the thread the right tension to form the stitch. They may vary from sewing machine to sewing machine but you typically have: a) an upper thread guide, b) a thread take-up lever, and c) a lower thread guide.

Stitch selector
It is used for selecting the type of stitch you want to use. The dial is usually accompanied by a stitch chart directly printed on top of the machine including the mostly used stitches. This is handy, as you don’t have to go back to your instruction manual, everytime you want to select a different stitch. Stitch icons are usually also printed on the selector.

Reverse lever
This control allows you to backstitch, i.e. sew backwards. This is used to secure your stitches at the beginning and/or at the end of your seam. The machine will sew in reverse as long as the lever is down, once it is released it will proceed sewing forward.

Needle and needle threader
The needle is attached to your machine via a screw. Most machines usually come with a small screw driver in their kit that you can use everytime you want to change your needle. There are different types of needles for different purposes (check out this post), depending on the fabric you may want to use a general-purpose needle, a ball needle for knits, a denim needle, and so on. Most sewing machines also come with a needle threader that facilitates threading the needle.

Presser foot and presser foot lifter
This is the part of your sewing machine that takes care of holding your fabric down while sewing. The presser foot is attached to the foot holder via a screw. There are different presser feet for different purposes. Sewing machines usually come with a small selection of presser feet suitable for common projects (e.g. zipper foot, overedge foot, blind stitch foot, buttonhole foot, etc.), but you can always buy more presser feet for special projects. Presser feet are mostly standard but there are a few different types, depending on the brand of your sewing machines. You can either buy a presser foot specifically made for your sewing machine model or universal feet that are usually cheaper. Just make sure that they are compliant with your model.
Presser feet can be easily detached by pressing a small lever on the back. For some feet (which come with a non-detachable foot holder) you might need to fully detach your foot holder unscrewing the screw.
The presser foot lifter is used to lift the presser foot up.

Feed dogs
The feed dogs take care of moving your fabric while the machine is running to form consecutive stitches. In some cases you may want to drop the feed dogs and manually feed your fabric into the sewing machine. There is a drop feed lever for this, usually located on the back of the machine.

Throat plate
The throat plate lies below the presser foot and accommodates the feed dogs and the hole through which the thread is pushed to form the stitch. In order to take care of your sewing machine maintenance you need to remove the needle plate by unscrewing the screws that hold it in place to access the bobbin case.

Presser foot dial
This dial is used for adjusting the pressure of the presser foot. This setting depends on the thickness of the fabric: the thicker the higher the pressure needs to be. For ordinary fabrics you can just use a medium pressure setting, lower pressure is suggested for finer fabrics, whereas higher pressure is suitable for heavyweight fabrics.

Handwheel
You can use the handwheel to manually move the needle up/down. This is also useful when sewing tricky seams where you want full control of your machine. For most machines, the handwheel is indispensable for bringing the bobbin thread up before starting sewing. Higher-end machines automatically take care of this step for you.

Knee lifter
Believe it or not, this thing just changed my life! You plug the knee lifter into a small hole on the bottom right of your machine and you can control your presser foot just using your knee. Do you know what does this mean? That you can freely handle your fabric with both hands while your knee is doing the job. I have to admit that it took me some time to synchronise my body movements and not getting confused between pushing the foot control and using the knee lifter. But once you get used, it just saves you tons of time. Think about it. Let’s say you were sewing around a corner. Without the lifter you’d have to stop, lift your presser foot with your right hand while the left hand is holding the fabric trying not to mess up. Then you’d use both hands to pivot the fabric around the corner, put the presser foot back down and realise that you’re not perfectly aligned so… presser foot back up with your right hand, fabric back to the initial position, presser foot down, another few stitches, presser foot back up… did you get the point? With your knee lifter this is gonna be sooo much faster, you can’t imagine!

Electronic sewing machines

Stitch selector
In electronic sewing machines everything is taken care of by a computer so you won’t have any dial, just a number of function keys to select your stitches. Depending on how many stich types your machine comes with, you might have all the stitch keys with printed icons on top or just the mostly used ones and then numerical keys to select the others. You will find a full stitch chart in your instruction manual. An LCD display typically provides a number of information about the selected stitch, stitch length and width and other possible settings.

Speed control slider
Higher end electronic machines come with a speed control slider. This is actually a great feature to have as it allows to set the maximum speed at which you want you sewing machine to sew. Basically, if you select medium speed, when you push your foot control all the way down the machine will only go half the speed it is capable of. This is particularly useful when sewing tricky seams as it gives you full control of the machine!

Thread cutter button
Here’s another great feature of modern electronic sewing machines! When you press this button the upper thread is brought at the bottom of the fabric, knotted with the lower thread and automatically cut for you, so you can directly pull your fabric off and keep going with your project! If you don’t have an electronic machine your thread cutter will be a small blade close to the presser foot, but in this case you’re gonna have to bring your thread up there to cut it.

Needle up/Down button
This control allows you to bring the needle up or down.

Reverse button
This control allows you to backstitch, i.e. sew backwards.

Start/stop button
In electronic sewing machines the stitching is fully controlled by a computer, so you can actually sew without using the foot control pressing the start/stop button. Personally, I find it much better to sew using the foot control, as I feel like having much more control over my machine. But it might just be that I got used to it! This start/stop button actually comes handy when sewing things such as (automatic) buttonholes, as your machine will be in function until completing the buttonhole without needing you to keep your foot pushing down the pedal all the time.

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