Serger Stitches: Overlock Stitch, Flatlock, Rolled Hems & More

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A serger, or overlocker, is a specialized sewing machine that uses multiple threads to create strong, flexible, overcast seams and decorative edges. Like all sewing machines, a serger is built to make certain stitch designs, and these stitches can vary from machine to machine.

What are the most common types of serger stitches? How do you create them, and what are they used for? We’ll lay it all out for you here in today’s post.

Serger Stitches: An Overview

If you’ve used a regular sewing machine, you’ll know that each machine comes with built-in stitches. Some machines, like a straight-stitch quilter, have only one built-in stitch design. Others, like the Quantum Stylist 9960, may have hundreds.

In addition to the built-ins, there are ways of expanding your machine’s catalog of stitches by adjusting parameters like stitch length, stitch width, and so on. You may, for example, recognize that a zigzag stitch with zero width can be used the same way as a satin stitch. 

Some manufacturers call this second type of stitch a “stitch option,” “stitch function,” “stitch configuration,” and suchlike.

The stitch catalog of a serger is very similar. Each machine comes with a complement of built-in stitches. By making adjustments to these, you can create additional stitches.

Like the stitches of a standard sewing machine, the different serger stitches have different uses.

Serger Stitch Parameters

With very few exceptions, sergers are mechanical. That is, you make adjustments with knobs, levers, switches, and sliders. There is rarely an onboard computer. Some adjustments are made in the same way on a serger as on an ordinary sewing machine. Others are made differently.

On a serger, these are the parameters you’ll need to adjust.

Number of Threads

We mentioned that sergers sew with multiple threads. But exactly how many?

Most home sergers can make stitches using two, three, and four threads. Some budget models sew with three or four threads only. A very few sew with two or three threads, and you can find premium models that sew with up to eight.

SINGER | Professional 14T968DC
The Singer Professional 14T968DC is a fine example of a 2-3-4-5 serger suitable for a home sewing room

In general, the heavier your fabric, the more threads you’ll want to use. So delicate edgings on ultralight fabrics most often consist of two-thread stitches. Stress-bearing garment seams, on the other hand, will do better with three, four, or more threads.

Number of Needles

janome mod 8933 needle plate presser foot
The two needles of Janome’s MOD-8933 serger in action

Most sergers have two needles and two loopers. Needles sew straight rows, while loopers cast thread around seam edges to seal them off. 

Some serger stitches use both needles and both loopers. Other stitches may use only one needle and either one or both loopers.

Choosing the right or left needle is one way of adjusting the width of a serger stitch. There are others, though, and we’ll discuss those in a bit.

Stitch Length

Stitch length adjustments are very similar on sergers and manual sewing machines. Most will have a stitch length adjustment knob or dial.

Stitch Width

baby lock celebrate adjustable stitch width
The stitch width dial on the excellent Baby Lock Celebrate serger

Stitch width adjustments, on the other hand, can be very different. A few sergers have a stitch width adjustment knob. However, on most sergers, you’ll have to use one of these other methods.

For single-needle stitches, using the right needle makes a narrow version of the stitch, for instance, a narrow rolled hem. Using the left needle makes a wider version of the same stitch.

You can also adjust the cutting width, that is, the amount that the cutting knife trims off the edge. 

Some models will require you to adjust the stitch finger. You might have to move the stitch finger, switch it out for a different one, or remove it altogether.

Thread Tension

brother 1034d tension dials
The colorful tension dials of the Brother 1034D

On a regular sewing machine, you generally adjust the tension of the top thread. Occasionally, you might address the bobbin thread tension. But on a serger, every thread has its own tension dial. And adjusting the thread tensions relative to one another is another way to create different stitches.

Differential Feed

Janome 634D MyLock differential feed
The differential feed ratio indicator window (A) and the differential feed dial (B) on a Janome 634D

A regular sewing machine has one set of feed dogs that feed your fabric through the machine. A serger has two. The differential feed adjusts the speed of the two sets of feed dogs relative to one another. This, in turn, increases (or decreases) the amount of stretch or compression of the fabric during sewing.

Adjusting the differential feed makes it easier to sew knits and stretch fabrics. But it’s also how you create special types of decorative effects like lettuce edges, ruffles and pintucks.

Serger Stitches and How to Use Them

So, what are the most commonly used serger stitches? And if they’re not already built into your machine, how do you create them from the stitches that are?

It’s time to find out!

Overlock Stitches 

The overlock stitch is the fundamental serger stitch. Almost every serger will come with three- and four-thread overlock stitches built in. A 2-3-4 serger, like the SINGER 14HD854 for example, may also have a built-in two-thread overlock. 

You can adjust your stitch parameters to create narrow and wide versions of all of these. You can also adjust the tensions of different threads in order to create variations on the overlock stitches.

Two-Thread Overlock

A two-thread overlock stitch provides a sealed seam that’s ideal for lightweight fabrics. It’s also a good one to use if you want to minimize bulk in your seam. 

Two-thread overlock stitches are made using oneneedle thread and one looper thread.

Use your right needle to create a narrow two-thread overlock stitch. Use your left needle to create a wide two-thread overlock stitch.

Three-Thread Overlock

3 thread overlock stitch

A three-thread overlock stitch is one of the go-to stitches for garment construction. This stitch creates a strong, stretchy seam that’s great for use with a variety of fabrics.

Three-thread overlock stitches are created with one needle thread and both looper threads.

As above, use your right needle if you want a narrow three-thread overlock stitch, and your left needle if you want a wide three-thread overlock.

Four-Thread Overlock

4 thread overlock

A four-thread overlock stitch creates a sturdy seam that’s fit for use with a variety of thick and heavy fabrics. If you’re making bluejeans, for example, this is your stitch.

To create a four-thread overlock, you’ll be using both needles and both loopers.

Overlock Variations

You can adjust your machine’s parameters to create a few variations on the different overlock stitches. You may have to experiment a bit to get the stitches exactly how you want them. Your serger manual should have suggestions for exact settings.

Try these.

To create a two-thread overlock wrap stitch, use your right needle. Increase the tension on the needle thread and decrease the tension on the lower looper thread. Again, choose the right needle to create a narrow stitch, and the left needle to create a wider stitch.

To create a three-thread stretch overlock stitch, use your right needle. Increase the needle thread tension and the tension for the lower looper, while decreasing the tension for the upper looper.

3 thread stretch

Flatlock Stitches

3 thread flatlock -1

The flatlock stitch, as the name implies, creates an attractive, flat seam. The looper threads completely enclose the fabric edges, and the entire seam lies flat. It’s an excellent choice when you need a strong, enclosed seam but want to minimize bulk.

The original purpose of the flatlock stitch was to imitate a cover stitch. Today, you often see a flatlock stitch on seams for athletic wear. Flatlock stitches can also be used decoratively, as they create an attractive “ladder” effect on the reverse side.

3 thread flatlock -2

You might also know this stitch as a safety stitch or a ladder stitch.

Sergers can create flatlock stitches with two, three, or four threads. As with overlock stitches, you can make narrow and wide versions of one-needle flatlock stitches by choosing either the right or left needle.

You can create a flatlock stitch by threading your serger for an overlock stitch. Then:

  • Increase the needle thread tension, and
  • Turn the upper looper thread tension to zero, and
  • Increase the lower looper thread tension to the near-maximum setting

Tension control settings can vary from machine to machine. Your serger manual should be able to give you specific information about creating this stitch with your machine.

Rolled Hems

A rolled hem is an attractive way to secure the edges of a single layer of ravel-prone fabric. You often see a two-thread rolled hem on delicate scarves, for instance. The rolled hem is also the basis of a decorative lettuce edge.

3 thread rolled hem

Some sergers have a built-in rolled hem setting, which makes the necessary adjustments for you. However, if your serger doesn’t have a built-in rolled hem, it’s not difficult to make the adjustments yourself.

Rolled hems come in two-thread and three-thread varieties.

First, disable or remove the cutting blade. A rolled hem rolls the edges out of the way, rather than trimming them. Many sergers have a retractable blade, but even if yours doesn’t, it should be easy to remove it.

Next, choose a needle. Whether you’re sewing a two-thread rolled hem or a three-thread rolled hem, this is a one-needle stitch. The same rule applies as in the stitches above; use the right needle for a narrow rolled hem or the left needle for a wider rolled hem.

If you’re making a two-thread rolled hem, you’ll also want to use the upper looper converter that came with your serger.

serger upper looper converter

Mock Safety Stitches

The mock safety stitch comes in three-thread and four-thread varieties. This is a strong, flexible stitch used for stress-bearing garment seams. The mock safety stitch is meant to emulate a five-thread safety stitch. It’s not quite as strong, but it does very well for itself.

The mock safety stitch uses both looper threads and either one or two needle threads

The mock safety stitch is a built-in type stitch, which comes with some, but not all overlock sergers.

Decorative Stitch Examples

Sergers are made primarily for construction, and generally do not come with decorative stitches, however, there are always exceptions. Though you won’t find a serger with a large selection of decorative designs like the best computerized sewing machines, you may come across a serger with one

Here are a few examples.

Picot Stitch

3 thread picot

The picot stitch is a delicate scalloped shape that can give a lovely finish to cuffs, collars, scarf edges, and so on. It comes as a built-in stitch on a few serger models. 

You can also create a picot edge on a regular serger.

First, set your machine to do a rolled hem. For this example, I’m doing a three-thread picot stitch.

Next, increase your stitch length. I’ve set mine to 4, which is the maximum length on my serger.

Now increase your lower looper tension so that it pulls the upper looper thread around to the other side. I’ve set my lower looper tension to my machine’s maximum setting.

And don’t forget to retract your cutting blade!

Wave Stitch

The Wave Stitch is a proprietary stitch that comes built into some Baby Lock machines, like the Baby Lock Imagine Wave BLE3ATW. You can see what it looks like here.

The wave stitch can be used on its own, but you can also use it as the basis for other stitches, such as a wave flatlock stitch. 

Two Blanket Stitches

3 thread blanket

The blanket stitch is a popular edging on, unsurprisingly, blankets and appliqué pieces. This is a wide two or three-thread stitch, and it’s easy to make on any serger.

First, remove the right needle.

Next, set your machine for a rolled hem. That includes retracting your cutting blade.

Now, set the needle tension to a standard, or middle setting. Set the upper looper thread to its maximum, and the lower looper thread to zero. This will pull the lower looper thread to the top side of the seam to give your blanket stitch its characteristic look.

You may have to experiment to get it where you want it to be on your machine.

Chain Stitch and Cover Stitch

The chain stitch and cover stitch are the two fundamental stitches you’ll find on a coverstitch machine. In general, a serger will not make either of these. This is because sergers are typically used to make seams, while a coverstitch machine’s main job is hemming. (Confused? Check out our post on the differences between sergers, overlockers, and coverstitch machines)

However, there are hybrid sergers that do both overlock sewing and coverstitch sewing. So it’s worth understanding what these stitches are and what they’re used for.

Chain Stitch

If you do embroidery or crochet, you’re already familiar with a chain stitch. A machine chain stitch is very similar. It can be used on its own or to connect two rows of straight stitching on the reverse side of the fabric. You can also use a chain stitch decoratively on the right side of the fabric.

Watch how it’s done here.

Coverstitch

A coverstitch is a compound stitch consisting of two parallel lines of straight stitching on the right side of the fabric connected by a chain stitch on the reverse side. This creates a professional sealed hem that is both strong and flexible.

Serger Stitches: Which Overlock Stitch Do you Love The Most?

Every serger comes with a catalog of built-in stitches. These built-in stitches vary from machine to machine but, with few exceptions, every serger will make a three-thread and four-thread overlock stitch. 

By altering parameters like stitch length, stitch width, and the relative tensions of each of the threads, you can create additional stitch designs and extend your repertoire.

What are your favorite serger stitches? Do you have any advice for our readers? Tell us all about it in the comments!

overlocker stitches

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