# How to thread an overlocker

Source: https://stitchandhem.co.uk/blog/how-to-thread-an-overlocker
Published: 2026-10-12
Publisher: Stitch and Hem

**In short:** Thread an overlocker in the order your manual gives, following the colour coded guides for each thread. On many 4 thread machines the order is upper looper, lower looper, then right needle, then left needle, because the loopers must sit beneath the needle threads. To change colours without rethreading from scratch, tie the new threads onto the old ones and pull them through.

Threading is the part of owning an overlocker that puts many people off. With four or more threads, two loopers and two needles, it can look like a puzzle. In practice, once you understand why the order matters and learn the tie-on method, threading becomes routine. This guide explains the usual threading order on a 4 thread overlocker, walks through each step, shows how to swap colours quickly, and explains what an air threader does. Always keep your machine's manual to hand, because the exact thread path differs between models.

## Why threading order matters

An overlock stitch is built from looper threads that wrap the fabric edge and needle threads that lock them in place. The lower looper thread has to pass beneath the upper looper path, and the needle threads have to pass through the loops the loopers form. If you thread the needles first, they can block the looper paths, and if a looper is threaded out of order, the stitch will not form or the thread will snap.

On many 4 thread overlockers the common order is upper looper, lower looper, then right needle, then left needle. Some machines, particularly those with air threading or a different looper design, use a different sequence. Treat the order here as a general guide and follow the colour coded guides on your machine and the threading chart in its manual or inside the front cover for your model.

## Before you start

Good light and a little preparation make threading far easier. Raise the presser foot, which releases the tension discs so the thread can seat between them. Turn the handwheel towards you to bring the needles to their highest position. Open the front looper cover and, if your model has one, the side cover. Have tweezers to hand; most overlockers come with a pair for reaching the looper eyes.

- Pull the telescopic thread stand up fully so the guides sit directly above the cones
- Place the cones on the spool pins with cone holders or spool caps as the manual shows
- Raise the presser foot and bring the needles to their highest point
- Open the looper cover and check the colour code for each thread path

Note: Switch off and unplug the overlocker before opening the looper cover, threading the loopers or changing needles. The knife and loopers move when the handwheel turns. If the machine jams, the knife will not cut or the timing seems wrong, take it to a qualified sewing machine engineer rather than opening the casing.

## Step by step: threading a 4 thread overlocker

The steps below follow the common order on many 4 thread machines. Each path has its own colour, often shown as dots or lines next to every guide, so follow one colour at a time from the cone to its looper or needle. Pull each thread firmly into its tension disc so it clicks between the plates.

1. Upper looper: take the thread through the stand guide, into its tension disc, then follow the coloured guides down to the upper looper and thread its eye. Leave a tail of around 10 cm.
2. Lower looper: thread through the stand guide and tension disc, then follow its guides. Turn the handwheel if needed so the lower looper is in the position the manual shows, and thread its eye with tweezers.
3. Right needle: take the thread through the stand guide, its tension disc and the needle guides, then thread the right needle from front to back.
4. Left needle: repeat for the left needle, keeping the two needle threads separate in their own guides.
5. Pull all four tails under and towards the back of the presser foot, lower the foot and turn the handwheel slowly a few times.
6. Sew a test chain without fabric, then sew on a scrap of the fabric you plan to use and check the stitch.

## The tie-on method for changing colours

If the machine is already threaded and stitching well, you rarely need to rethread from scratch. Instead, cut each old thread near its cone, tie the new thread on with a small, secure knot, and pull the new threads through the whole path. This keeps each thread in exactly the right guides.

Raise the presser foot first so the tension discs open, then pull each thread through gently until the knots reach the loopers. Most knots will pass through looper eyes, but they usually will not pass through a needle eye, so cut the needle threads just above the needle and thread the eyes by hand. Trim the ends of the knots short so they slide through the guides easily.

1. Cut each old thread close to its cone and remove the old cones.
2. Place the new cones and tie each new thread to the matching old thread with a small knot.
3. Raise the presser foot so the tension discs release.
4. Pull the looper threads through one at a time until the new colour comes out of each looper eye.
5. Pull the needle threads until the knot reaches the needle, cut above the knot and thread the needles by hand.
6. Sew a test chain and check the stitch on a scrap.

## What an air threader does

Looper threading is the fiddliest step on a conventional overlocker, because the lower looper path in particular has several guides tucked inside the machine. Air threading overlockers replace that path with small tubes. You feed the thread into the tube entrance, press a lever or button, and a puff of air blows the thread through to the looper.

This makes looper threading much quicker and avoids having to use tweezers inside the machine, which is why air threading is popular with beginners and anyone with less nimble fingers. Air threaders are usually found on higher priced models, and the needles are still threaded in the usual way on most machines. You can compare models with and without this feature in our [best overlockers for beginners](https://stitchandhem.co.uk/best/best-overlockers-for-beginners) guide.

[Find an easy to thread overlocker](https://stitchandhem.co.uk/best/best-overlockers-for-beginners)

## Troubleshooting a newly threaded overlocker

If the stitch does not form, the most likely cause is a thread missed from a guide or tension disc, or threading in the wrong order. Rethread the loopers first, then the needles, and check each thread is seated between its tension discs. Loops hanging off the edge often point to the upper looper tension; threads pulled to the underside usually point to the lower looper. Change one tension dial at a time and test on a scrap.

If threads snap repeatedly, check that the thread is not catching on a cone notch, that the stand is fully extended and that the needles are the correct type and inserted fully. Our [overlocker vs coverstitch](https://stitchandhem.co.uk/blog/overlocker-vs-coverstitch) article explains the parts of the overlock stitch, and the [differential feed explainer](https://stitchandhem.co.uk/blog/overlocker-differential-feed-explained) covers wavy or puckered seams.

## Frequently asked questions

**What order do you thread an overlocker in?** On many 4 thread overlockers the order is upper looper, lower looper, then right needle, then left needle. Some models differ, especially air threading machines, so always follow the colour coded guides and the threading chart for your model.

**How do I thread a Brother overlocker?** Brother overlockers have colour coded paths printed inside the looper cover and a threading chart in the manual. Follow the order shown there for your model, rather than a general sequence, because looper positions and guides vary between machines.

**Why does my overlocker thread keep breaking?** Common causes are a thread missed from a guide, a thread not seated in its tension disc, a bent or wrong needle, or the thread stand not fully raised. Rethread in the correct order with the presser foot up and test again.

**Is an air threading overlocker worth it?** If you find looper threading frustrating or change colours often, air threading saves a lot of time. If you mostly sew with one colour of thread and are comfortable with tweezers, the tie-on method makes a standard overlocker manageable.

## Buying guides on this topic

- https://stitchandhem.co.uk/best/best-overlockers-for-beginners
- https://stitchandhem.co.uk/best/best-coverstitch-and-combination-overlockers
- https://stitchandhem.co.uk/best/best-sewing-machines-for-dressmaking