How to Thread an Overlocker

An overlocker, which is otherwise known as a serger, gives garments and other sewn projects a professional finish. With the help of an overlocker, you’ll be able to sew seams, cover raw edges with overlock stitches, and trim any excess fabric from garments.

While overlockers offer a huge dose of versatility in your creative pursuits, the threading process can be quite intimidating because overlockers use 3 to 5 spools of thread all at once. However, learning how to thread will get easier with enough patience and practice.

The instructions provided below assume that you’re using a 3 or 4-thread overlocker. That said, the steps might vary slightly depending on the make and model of your machine, so it’s always prudent to have your manual close by for reference too.

Things You Will Need

Before embarking on the threading process, you’ll need 4 cones of thread, hook-nose tweezers, and a piece of fabric to test the machine once threading is complete.

Once you’ve gathered the necessary supplies, you’ll need to follow the correct threading sequence. To avoid thread jams, always thread your machine in this order:

1. Upper looper
2. Lower looper
3. Right and left needles if you’re using a 4-thread overlocker.

How to Thread an Overlocker

Before you begin threading, make sure to turn off your machine and set tension to zero. Next, pull up the telescopic thread bar at the back before positioning your four thread cones on the spindle holders.

After positioning the cones, the thread will go up into the corresponding loop at the top of the telescopic bar. As the thread comes down, slide it under a hook positioned just where the grooved thread channels begin. The thread will then run along that channel toward the front of your machine.

At the edge of your machine, you’ll need to run the thread between two metal discs of the tension dial. Up until this point, steps for threading the needles as well as upper and lower loopers are exactly the same.

The threading process changes slightly for every spool of thread after going past the tension discs. As such, the steps can be broken down into the following based on the previously mentioned overlocker threading sequence:

Upper and Lower Looper Final Threading Steps

Upper and lower looper threads continue their path along the next part of the grooved channel that runs downward on the front part of your overlocker. The threads will then snap into another thread guide underneath.

From here, things get a little tricky. You have to rotate the hand wheel to access the final hooks of the upper and lower looper. Once the thread goes through those attachment points, it will pass under the presser foot and off to the side. It’s always important to leave at least 10cm of thread tail for each spool.

While the final part of threading the upper and lower looper may sound complex, the steps are easier to follow than you think. Most overlockers also provide a threading guide with diagrams, which can be either on-board or inside the instruction booklet.

What’s more, some brands colour-code the attachment points for the upper and lower looper with dots. That being said, you’ll still need to use a pair of tweezers because some of the hooks inside the hand wheel can be difficult to access.

Right and Left Needle Final Threading Steps

After passing through the tension discs, thread for the right needle goes under two hooks (one small and the other slightly larger), then over an upper thread guide.

This is the same for the left needle thread, except that it only passes under the larger hook and over the lower thread guide (check your manual as steps will vary depending on the brand).

Finally, thread each needle and bring the two tails (at least 10 cm each) under the presser foot then to the left of your machine together with thread tails coming from the loopers.

Test the Machine after Threading

Once threading is done, you can now test your overlocker to evaluate the stitch quality and ensure that there are no snags. First, re-set the tension dials to 3 and plug in the power cord. Next, lower the presser foot and move the thread tails at the back of your machine. Engage the presser foot as you stitch a little chain on a piece of fabric. The machine should create an overlock stitch without jamming.

Threading Tips: The Dos and Don’ts of Threading an Overlocker

When learning how to thread an overlocker, there are a few dos and don’ts you need to know. Knowing what to do and avoid will limit any chances of mistakes. For the best results:

  • Always thread one reel/cone at a time, starting with the lower looper followed by the upper looper and finally the right and left needles.
  • Keep the tension at zero while threading. This sets the tension discs at their most open positions, thus ensuring that thread will pass smoothly without any snags.
  • Read your instruction manual and study any threading diagrams that come with your machine.
  • Apply a little wax at the ends of your thread so that it will be easier to thread the needles and loopers.

Top Threading Pitfalls to Avoid

  • Do not use woolly thread, which is also referred to as “floss” or “flock”. Such thread keeps breaking, jamming, and can even break the needles.
  • Try not to use a larger cone for one looper and a smaller reel for the other looper as this could result in uneven tension.


Keep in mind that this tutorial is just a basic guide on how to thread an overlocker and it should by no means replace the instruction manual provided by your manufacturer. While threading an overlocker may sound complicated, with time, patience, and practice, know that you can learn how to thread an overlocker in as little as five minutes.