Serged Seams – Sewing and Finishing with a Serger

Learning how to sew serged seams is one of the best ways to create professional-looking seam finishes quickly and efficiently. Sergers, also called overlockers, trim raw edges, sew the seam, and finish the fabric all in one step. This creates neat, durable seams that resist fraying while remaining flexible and comfortable to wear. Serged seams are especially useful for knit fabrics because the overlocking stitches stretch with the fabric rather than break. In this tutorial, you’ll learn how to sew serged seams step by step, the different types of serger stitches, and how to use serged seams on woven fabrics, curves, denim, and French seams.

What Are Serged Seams?

The serger can either do an all-in-one process where it sews the seam and neatens at the same time, or you may just want to stitch as normal, and serge afterward to neaten off the seam. Serged seams are particularly useful for knit fabrics as they produce an elastic seam with stitches that will not break.

If you are learning professional seam finishing methods, explore the full types of seams guide to compare serged seams with other seam finishes.

How to Sew Serged Seams (Step by Step)

Here are the steps to take to complete straightforward serged seams:

1. Test with Scrap

The first step is to practice your serger stitch on a scrap of fabric you plan to sew.  The loopers and the stitches, and the tension of the serger must be regulated to fit with the fabric. 

The serger is going to cut as well as stitch. For this reason, the tension and seam width must be exactly as you would like them to be. If this is your first time, read how to use a serger before you start.

2. Baste the Seam

Prepare your seam. Sewing with a serger, and knowing your machine is going to cut and trim, means you must avoid using pins where possible. Your machine blade will get damaged if it rides over a pin. 

2 alternatives to using pins:

• You can baste the seam by hand first.
• Machine stitch a basting row of straight stitch with your regular sewing machine.

If you are making a pattern you know well or an easy-to-make style you may feel confident to sew freestyle without pinning or basting. 

3. Serging the Seam

Get ready to serge along the seam, and watch how your machine can cut, sew, and neaten all in one swoop. You will feel confident in this step if you have prepared and practiced.

Tips for sewing a serged seam:

• When starting, you do not need to lift the foot to place the edge of the fabric under like you do with a regular sewing machine. The fabric will feed forward under the foot.
• Use the stitch guide on the side of the machine to ensure you are sewing theline at the correct width.
• Make sure you leave a ‘tail chain’ at the beginning and the end of the serging stitch. There is no backstitch on the serger. 

4. Finishing

The chain can be threaded back on itself using a large eye needle to thread the chain tail and push it back through the stitching. Threading the chain back on itself is essential to the finishing-off process and ensuring there is no seam unraveling. Alternatively, cut the chain tail with sharp scissors and use fray check on the ends to prevent unraveling.

These four steps form the basics of seam neatening and sewing serged seams.  There are some other techniques and variations to consider depending on the garment, the fabric, and the amount of strength required from the seam.

Types of Serged Seams

Knowing the serger’s stitch capacity is important for neatening your seam. Different sergers produce different stitching depending on the number of threads they support. 

Sergers come in different sizes and models. They have different numbers of threads and may do a double line of stitching, or a single, depending on how many needles you thread. A typical number of threads are 3,4 or 5.

• The more threads on the machine, the stronger and wider the sewing will be. 
• Even if the machine has up to five threads there is no need to use all the threads. It is possible to sew with the serger and use fewer threads. 

The important thing is to ascertain the number of threads that best suit the fabric you plan to sew and to practice on a scrap first.

Advantages of Serged Seams

A serger is not an essential piece of equipment to sew and neaten beautiful seams. However, the advantage of the serger is its ability to finish everything all in one motion. It is a machine that makes your sewing look professional. 

Serged Seams vs Regular Sewing Machine Seams

Serged Seams	Regular Sewing Machine
Trim and finish edges together	Usually requires separate seam finishing
Stretch with knit fabrics	Straight stitches may snap on stretch fabrics
Fast professional finish	Slower multi-step seam finishing
Uses loopers and multiple threads	Usually uses a single needle and bobbin
Ideal for overlocking raw edges	Better for precision construction sewing

A serger is helpful but not essential for sewing.

Serged Seams with Corners and Curves

See my article on how to use a serger for extra information and tips on sewing corners and curves for your serged seams.

Other Serged Seams

Here are some other ways to use the serger to neaten:

Closed

• Sew your seam with your regular sewing machine along the seam allowance.
• Finish the edges together with your serger and press the seam to one side.

This is the basic seam using the serger with the straight sewing threads forming the seam and the looper threads making the overclocking edge.  It is your choice as to whether you need three or four, or five threads for your all-in-one closed seam on the serger.

Open

There are two ways you can sew open seams on the serger by altering the order of the steps.

Sewing the Seam First – Stitch the seam with your regular sewing machine along the seam allowance. Finish each raw edge separately with the serger, then press the seam open.

Serging First – You can also finish the edges first before you sew the seam. Neaten the raw edges and take into account how much of the seam allowance has been trimmed by the serger. You could also choose just to overlock and disconnect the blade of the serger and not have any of the seam allowance trimmed.

When the edges have been serged and trimmed, sew your main seam with less allowance and press the seam open. 

A Serged French Seam

It is possible to use the overlocker to start your French seam and get a really neat edge. This is a great way to take advantage of the serger’s ability to overlock and trim. 

1. Set the serger on a narrow three-thread setting
2. Put your fabric wrong sides together and overlock the first part of the French seam. 
3. Press the seam and turn it to allow the right sides to meet. The serged part will be enclosed. 
4. Use your normal machine to stitch down and complete the French seam.  The neatly overlocked edge will be enclosed in the French seam.

The Number of Threads in Serged Seams

1. Two Thread or Flatlock Stitch – This interesting stitch joins two pieces of fabric together, and the seam, including its neatening, is pulled open to lie flat. The finished seam has a ladder effect on one side with two rows of parallel stitches on one side of the seam and the looper stitches on the other side.
2. Three Thread Serged Seams – The three-thread stitch neatens the seams of stretch fabrics. The three-thread serged seam is a narrower seam and not as strong as the serger stitched with four threads.
3. Four Thread Serged Seams – The four-thread finishes off a strong seam with a neat finish. It has an extra stitch through the middle of the over-locking threads. This extra stitch is known as a safety or extra-strength stitch.

Overlocker for Denim and Heavy Duty Fabrics

The serger is a really good way to prevent fraying in denim or other heavy-duty fabrics. Try your serger out on your denim fabric sample using two pieces of denim together to check that the fabric is not too thick for your serger.

If your model is reluctant to sew two pieces of fabric together, then neaten each side separately. Use the serger to neaten raw edges before starting to sew the seams. In this way, the seam is neatened, and fraying is prevented before the seam is sewn together. 

1. Pass the fabric through the serger carefully. Do not be tempted to pull the denim through the serger, as this may cause the fabric to stretch or pull out of shape. It may cause the serger to stitch incorrectly and lose tension, causing the threads to tangle or snap. 
2. After the neatening is complete, sew the seams together with your normal machine and press the edges that have been overlocked open.

The serger is ideal for neatening seams of heavy-duty fabrics that fray easily.  The neatened serger edges of heavy-duty fabrics, hidden inside a lining of a jacket, for example, make sure the seam will not fray. 

Common Serged Seam Mistakes and Tips

Common Mistake	Tip for Better Results
Serging over pins damages the blade.	Remove pins before serging.
Fabric stretches while sewing.	Adjust differential feed settings.
Thread chains unravel after sewing.	Secure thread tails properly.
Tension settings create loose loops.	Test settings on scraps first.
Heavy fabrics jam the machine.	Serge layers separately if needed.
Fabric edge curls while serging.	Reduce tension or adjust stitch width.
Knits wave along the seam.	Use differential feed correctly.
Serging trims too much seam allowance.	Guide fabric carefully beside the blade.

Serged Seams FAQs

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Serged Seams – In Conclusion

Serged seams are one of the fastest and most professional seam finishes for both woven and stretch fabrics. Their ability to trim, sew, and overlock in one step makes them ideal for modern garment sewing. Once you learn how to sew serged seams, you can create cleaner, stronger garments with flexible, professional-looking seam finishes.

More Types of Seams

• Plain Seams
• Open Seams
• Closed Seams
• Princess Seams
• Bound Seams
• French Seams
• Grading Seams