Creative articles about sewing

Coverstitching on the BERNINA L 890, Background Knowledge, Part 1

Manu from and author for the German BERNINA blog is going to show you how to coverstitch on the BERNINA L 890, a combined overlocker/coverstitch machine.

Background Knowledge on Coverstitching, Part 1

I hear again and again that sewing coverstitch seams is so difficult and mysterious If you deal with the topic a little, but you realize: Coverstitching is not that difficult! Let us open that book of mysteries and today we will work with part 1

I’ll show you the coverstitch on the BERNINA L 890, an overlock/coverstitch combo machine. I hope you will know after part 3 of this series at the latest why Coverstitching is really fun – and why I particularly enjoy covering with exactly THIS machine.

Image of BERNINA L 890.


The L 890 is perfectly suited for working with all types of fabrics, including knits as well as wovens. With One-Step BERNINA Air Threader ✓ Intuitive operation via touch screen ✓ Fast, precise & quiet ✓ Manufactured by BERNINA ✓ 100% designed and engineered in Switzerland ✓ 

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First of all, however, we are looking at the question:

What is a coverstitch seam?

The coverstitch seam comes from the clothing industry. A cover stitch consists of two to three needle threads on the top and a looper thread on the back of the fabric. The chain stitch, also sewn on the coverstitch machine consists of a needle thread and a looper thread. Cover and chain stitch seams offer the possibility of sewing in the middle of the fabric. These seams can be used in a variety of ways, both for utility and decorative purposes, e.g. for seams, hems, belt loops, and much more.

Cover stitches and chain stitches can also be used for sewing decorative seams on fabric surfaces. You can make a garment look very sporty, but also classic – depending on which yarn is used in which place and how.

Overall, it can be said: A machine with coverstitch function opens up new dimensions in sewing!

Which machine should you use for coverstitching?

When it comes to the question of the machine for covering, the decisive factor for many is how large the space to the right of the needle? It should be large enough to be able to “push through” what you sew in a relaxed way.

As long as you deal with smaller sewing pieces, a machine with a small space may be enough, but children get bigger, and men report at some point that they should perhaps be given a hoodie. Then it is better to keep an eye on the size of the space from the beginning. Here the BERNINA L 890 is definitely in the front row, because due to the really large space of over 14 cm to the right of the needle, a men’s hoodie fits through absolutely comfortably. Or a bathrobe made of terry cloth.

Now you may be wondering what exactly would have to go through the space to the right of the needles of said garments. In the case of the bathrobe, it could be the topstitching of the front closure or collar. If the front closure seam does not lead around the hood, it must lead around the neckline, thus the hood including lining will travel through the space to the right of the needles – and here the L 890 is my really faithful companion.

In the men’s hoodie, it could be the topstitching of the raglan seams. A bigger pattern MUST pass through the space – either the front/rear part or the raglan sleeve.

How do you thread the machine for coverstitch?

One fact that inspired me about the L 890 from day one was the threading. I don’t primarily mean the simplicity with which this is achieved, even if the One-step BERNINA air threader is very impressive. I mean the fact that at any time, even after weeks of sewing abstinence, I can sit down at the L 890, choose a seam and the machine guides me exactly through the threading process with a animated video. Sensational.

So I choose my seam: 3 Thread Coverstitch

… and navigate with this small arrow here through the menu, which should make it easier for me to thread. Whatever it does. I’m really shown everything from sewing foot lifting – every move step by step.

If, for example. I don’t know how to rearrange; I can have a small video show me what needs to be done. The machine supports me both in threading …

… as well as when re-threading. All I have to do is do what it tells me. Every little path and little hook is shown to me. If I stick exactly to what is suggested to me, I get 100% to the threading goal.

Setting the correct tension

The machine also sets the default tensions, I threaded the left and right needle as well as the looper. In the picture below you can see what the original setting of the tension is. If something had been changed there, the corresponding field would be yellow.

One or the other may now think that this is how the tensions should be. But they don’t have to because that’s really just a suggestion. How the tension really has to be, depends very much on the thread and fabric that is to be sewn. And here it makes a difference whether the fabric is thick or thin. Whether the desired seam should be stretchable or rather tight. And also, whether the fabric is extremely elastic or rather less. The picture above shows the tension view in large, in the picture below you can see the tensions with the other settings in the stitch view screen.

Now it gets tricky. Many sewists, wish to the machine to ALWAYS set to the perfect tension.  I believe that the sooner it arrives in people’s minds that this does not happen, the sooner everyone will find their way around. With the L 890, BERNINA takes a lot from me in a great way, but in the end, it remains my project and my desire for individuality and creativity, which I can only satisfy myself.

The mere fact that each fabric can be stretched differently and that different properties can be found in the material – from stretchable to less stretchable, from very thick to very fine, etc. – can already make large differences in the setting. So, no matter which machine you are sitting on, you have to do your own thinking. This is important! Of course, the easier it is to operate a machine, the easier it is. And here the L 890 again provides excellent support.

So, let’s get back to the tensions and the right attitude for my project.

The first seam

To begin with, I have a plain turquoise sweatshirt fabric, perfect for autumn hoodies, in which I want to add a lining with a single jersey in red.

In the settings it is a difference whether we sew a shirt made of single jersey (at the hem rather thin by only two layers of single jersey) or a hoodie, in which the single jersey runs as lining (rather thicker). Over the course of this blog post series, we’ll look at both.

I’m doing a first sewing test in two layers, one layer of jersey, one layer of sweat. I can strongly recommend such sample seams. Very important: Always make the sample with exactly the material and the grain that you will later use for the “right” seam. Now I may notice during the test sewing that I like the seam well. It is also stretchable. So, the L 890 has made a nice seam. The needle threads form soft straight lines and the looper thread lies softly underneath to allow the stretch needed for the seam purpose.

However, I notice …

…  that I see the needle threads on the looper side. On the left are small loops, and on the right are these small Vs, which are composed of one-half needle thread and one half looper thread.

So, I decide to re-regulate so that the seam becomes more beautiful. Whether this is smart, we will examine later.  Behind the small field, which I point to in the picture below, hides a function that should help to fix possible seam amendments.

Optimize stitches 

Choose the stitch optimizer function and look for the possible deviation from optimal. Different possible seam appearances are listed. Now it’s really just a matter of finding the picture of my sample in the listing and seeing which is the recommended improvement.

Of course, my threads are all white. For better clarity in the help menu of the machine, all threads have different colors. But no one would thread in the colors that are in the menu, but in the colors of the project to be sewn – so let’s stick to white.

We have the following to choose from in the menu:

  1. Needle thread (yellow or blue) forms loops on the underside
  2. Chain looper thread (purple) forms loops on the underside of the fabric
  3. Chain looper thread (purple) forms tunnel on the underside of the stitch
  4. Seam puckering, needle thread (yellow or blue) too tight

My problem is listed exactly, because I have loops on the bottom (problem 1); we have just established that.

So, I choose the 1st menu item:

By clicking on the problem, four solutions are suggested to me:

  1. Increase needle thread tension (yellow or blue)
  2. Reduce Cover looper thread tension (purple)
  3. Increase stitch length SL
  4. Checking threading path

Now it could be that someone does not know what his right solution is if all his threads are white. That’s why we take a look at the individual points and shed light on them.

Construction of a coverstitch

In order to know exactly which needle thread is which in solution 1, it is helpful to know how a cover seam is structured. It’s quite simple:

Our chain looper is below. As a result, this is the white thread that goes from left to right on the underside.  This is exactly where the decisive factor for the needles is – it comes from the left, our looper. That is, it comes from the left, goes to the right, is caught by the right needle, and goes back to the left. So it pulls everything back to the left. The tighter it is, the more pull it has. As a result, the edge with the spikes (in the picture above the right side) is formed by the right needle thread, which cannot withstand the pull of the looper thread and is therefore pulled to the left. The edge with the loops is the right needle thread

Increase Needle Thread Tension

So we would now choose solution 1, that is…

  1. Increase the needle thread tension (yellow or blue)

…in order to achieve a stronger pull against the looper and create smooth edges, a tunnel may form because the amount of looper thread is not enough to form a clean seam from the far right to the far left. Tunnel formation could occur because the looper thread would now tighten. Why? At the moment, we have established that the looper thread looks good and is lying flat. However, it is also accompanied by Vs coming in a short distance from the seam width. If we increase the needle tension, it no longer has these; it has to bridge the entire width “alone”. There is not enough looper thread for this. So the looper thread can’t do it and tightens/tunnels.

Therefore simply increasing the needle tension cannot be the solution. This means that it is absolutely essential to look at the whole interaction between all the threads before just shooting off in one direction.

Reduce looper thread tension

So if we were to choose only solution 2 …

  1. Reduce Chain looper thread tension (purple)

… we loosen the looper thread tension and can thus bring more yarn into the seam. The needles then have less stress. Perhaps this would be enough to fix the “issues” of the seam. We will come to solution 3 and 4 later. So we first loosen the looper from currently 1.5 to 1 and leave the needle thread tensions where they are. We have two options for changing the tension: Either we use the display or the tension buttons – both deliver the same result. Our seam result now looks like this (the left seam):

I could imagine with a lot of goodwill that the V-shaped needle thread loops have become fewer – they actually are, but the difference is not so big that I want to jump into the air with joy. I don’t want to lower the tension of the looper thread any further at first, I would then have to bypass the air threader pipe. So, we increase the tension of the needle thread. We pull the left needle from 3.8 to 4.3, the right needle from 5.3 to 6.

The result is the left seam:

We don’t really have a visual change – why? Because we have changed too little! That’s the first thing I wanted to show: For something to change, a small step is not always enough. Sometimes it does. But the thicker the material,  and depending on the thread quality, decreasing tensions needs more than just a little. Sometimes I get messages with the content: “I have increased everything, but nothing changes”. Then it usually has to be increased further. But better first too little than too much!

Let’s bypass the compressed air to further reduce the tension in the looper thread. We leave the needle thread tension where it is. The left seam is the result:

Our jagged edge smoothes out slowly. Now we put on the needle thread tensions a little one last time, left needle on 5, right on 7:

You can now clearly see that, in contrast, there is much more looper yarn in the seam than in the first sample seam. The edges are also smoother.

I chose the small steps to show that sometimes they could be bigger steps.

The stretchability of the coverstitch

So why is this attitude better? Why not just pull the tension of the needle thread up and even higher? The answer is simple: It is always important to keep an eye on the elasticity and not to get a tunnel! We want a coverstitch seam that not only looks good, but is also stretchy. A coverstitch seam that does not tunnel. A simple increase in the needles would not only have led to a tunnel, but also to less elasticity in the seam. Why? Because there is less and less yarn in the seam.

So, in order to return to the above solutions, we opted for a mixture of options 1 and 2 and improved the seam appearance in favour of our stretchability.

The machine shows us what we have changed by highlighting the changes in yellow. With a click on the yellow we would come back to the default settings – in case someone should get lost in the settings. Incidentally, this is the case on all BERNINA machines with a screen, what has been changed is highlighted in yellow.

In this picture I am still on the way to the goal, but you can see the yellow highlighted changes.

That was part 1 of my little series of posts on sewing cover seams. In the next posts, we will look at what solution proposals 3 and 4 would have meant for our seam result. And how everything changes if we don’t take a sweat shirt, but 2 simple layers of single jersey

Until then, have fun covering!

Best wishes, Manu

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  • Djuna Bewley EditEditing comments on the BERNINA blog is only possible after logging in with a blog user account. Sign up now or create a user account if you do not have one yet.

    Thank you Manu! The in-depth illustration of how thread and looper tensions interact is invaluable.

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