The humble overlocker, (or serger as it is known in the USA) was invented around 1838 by J. Makens Merrow and his son Joseph Merrow in Connecticut, USA. It was originally designed to produce a crochet stitch but as time went on it developed in the clothing manufacturing hubs of Connecticut and New York, giving the 2, 3, 4 and 5 thread versions we see today.
So how does it work? Well it is a kind of crochet or knit stitch, with a needle thread (or 2) to hold it together. Not only does it stop the edge of fabric fraying, it also cuts the fabric as it stitches so a pattern can be followed to create a garment panel.
How is an overlock stitch formed?
- When the needle enters the fabric, a loop is formed in the thread at the back of the needle.
- As the needle continues its downward motion into the fabric, the lower looper begins its movement from left to right. The tip of the lower looper passes behind the needle and through the loop of thread that has formed behind the needle.
- The lower looper continues along its path moving toward the right of the overlocker. As it moves, the lower thread is carried through the needle thread.
- While the lower looper is moving from left to right, the upper looper advances from right to left. The tip of the upper looper passes behind the lower looper and picks up the lower looper thread and needle thread.
- The lower looper now begins its move back into the far left position. As the upper looper continues to the left, it holds the lower looper thread and needle thread in place.
- The needle again begins its downward path, passing behind the upper looper and securing the upper looper thread (the needle goes between the metal and the thread). This completes the overlock stitch formation and begins the stitch cycle all over again.
It’s worth remembering that this is happening 5,000 times a minute on industrial machines and 1,200 times a minute on domestic versions, so marvel at the engineering that allows that to happen with hardly a thread break! Indeed, they are very reliable pieces of equipment that, if basic maintenance and cleanliness are carried out, will give years of trouble free service.
Types of overlock stitch
Overlock stitches are classified in a number of ways. The most basic classification is by the number of threads used in the stitch. Industrial overlock machines are generally made in 1, 2, 3, 4 or 5 thread formations. Each of these formations has unique uses and benefits:
- 1-thread: End-to-end seaming or “butt-seaming” of piece goods for textile finishing.
- 2-thread: Edging and seaming, especially on knits and wovens, finishing seam edges, stitching flatlock seams, stitching elastic and lace to lingerie, and hemming. This is the most common type of overlock stitch.
- 3-thread: Sewing pintucks, creating narrow rolled hems, finishing fabric edges, decorative edging, and seaming knit or woven fabrics.
- 4-thread: Decorative edging and finishing, seaming high-stress areas, mock safety stitches which create extra strength while retaining flexibility.
- 5-thread: In apparel manufacturing, safety stitches utilizing two needles create a very strong seam.
Additional variables in the types of overlock stitches are the stitch length and the stitch width. The stitch length indicates how many stitches per inch there are, which is adjustable and can vary widely within one machine. Different stitch lengths create more or less dense and solid-looking edges. The stitch width indicates how wide the stitch is from the edge of the fabric. Lightweight fabrics often require a wider stitch to prevent pulling.
Adding extra variation in stitch types is the differential feed feature, which allows feed to be adjusted: extra-fast feed creates a ruffled or “lettuce-leaf” effect. Finally, some machines contain parts to roll the fabric edge into the stitch for added durability.
So, overlockers are reliable and capable of a host of different types of stiches for many applications in garment construction. It can be said that to get a professional garment construction finish, you need both a sewing machine and overlocker.
The fear factor – threading
Yep the dreaded threading! I always look at it this way: if someone has managed to design such a brilliant piece of equipment and all I have to do is thread it to get such professional results, it is worth the learning journey!
Those of us who have threaded early industrial overlockers, such as the Merrow, Wilcox & Gibbs T series or the Singer 246K series, where the threads ran through tunnels and you need a threader wire and the patience of Job to thread them wonder what all the fuss is about.
So how can we make the threading less arduous? It’s about the correct threading order. If you thread the needles before the lower looper, then the lower looper thread will always break, as the needle thread(s) will be on the wrong side of the lower looper thread and break it.
So this is the best threading order if threading from scratch:
- Upper looper (the smaller of the 2 loopers)
- Lower looper ( looks like an upside down ‘L’ or no ‘7’)
- Needle right
- Needle left (if applicable to the machine or stitch technique)
Ensure you thread through every thread guide and that the thread does not double wrap around anything. Also ensure the threads are firmly between the tension discs on each tension unit. It is also important to make sure that the thread does not twist around the needle when threading.
Once threaded, put all the threads under the presser foot (lower it) and turn the hand wheel in the sewing direction for the machine (usually shown by an arrow around the handwheel and most domestic machines turn the handwheel towards you) to establish a few stitches on a chain. Once done, slowly run the machine to increase the chain, then (having closed all the covers first) put under some fabric under the foot and have a go! Remember the stich is a continuous chain so you can run off the fabric. Also, the knives will be cutting so remember to leave a seam allowance for the knives to cut.
One knife moves and the other knife is fixed. If you have a thread running low, or need to change colour, then you can tie the existing thread to the new thread, and pull it through gently, remember to leave a long end to tie the new thread to. If it is a needle thread, the knot won’t go through the needle eye, but hopefully you will just have to thread that.
The looper threads are not seen on the good side of the fabric so you can go for a neutral thread here such as black, cream, grey, white. The needle thread is seen, so you could colour match here. The looper threads use approximately 4 times as much thread as the needle, which uses about the same as a sewing machine. So if you prefer, you can use a budget thread on the looper and a premium thread on the needle(s) for best results.
The needle matters too. Just as with your sewing machine, make sure you have a good sharp needle, of the right class for your machine (check the manual!) and of the right thickness for the fabric being stitched. We recommend a good quality needle such as Schmetz or Inspira for best results.
Some domestic overlockers are capable of being switched to a cover seam, (the seam you see on the bottom of a t-shirt) and a chain stitch. You can even use an overlocker to overlock and blind hem in one go with a bit of patience!
What can go wrong?
- The biggest single issue is a mis-thread. So if the stitch is not right, or a thread continually breaks then check the threading. Check the needle is good, of the correct type, inserted the correct way round and is pushed all the way up the clamp.
- Over time the machine will build up with fluff and lint, which will impair use, so look at the maintenance section in the manual and clean it regularly. When cleaning it out you can also give it a tiny drop of oil at the appropriate points.
- The sharpness of the knives will dull over time and may need replacing. If you have a needle breakage it may damage a looper surface, causing frequent thread shredding.
- Consider having your overlocker professionally serviced once in a while to keep it in tip top condition.
Buying an overlocker
Once you have read this blog, think about what stitches you might want to use. Ideally go for a demonstration and don’t be frightened to ask to see it on different fabrics. Ask how easy it is to thread, though don’t expect to be shown how until you buy it! Talk about the applications you might want, e.g. rolled hem, cover seam etc., and take some fabric to try.
I would be very careful about buying a sub £300 overlocker, you get what you pay for (and “buy cheap pay twice” certainly applies here). Think about the construction and design that had to go into producing the product. The components need to be of quality metals to give longevity and trouble-free service, and it needs to be easy to thread!
Here are some ideas, all of which come complete with free tuition and 2 year warranty.
The HUSKYLOCK™ S15 is a great 2, 3, 4 thread overlocker, with built in rolled hem. Flatlock is possible as it has a moveable upper knife and it has colour-coded threading and open thread guides, so it is easy to thread. It has a free arm, so you can put sleeves or trouser legs straight onto it.
The HUSKYLOCK™ s21 has 2, 3, 4 thread overlock, plus 2 or 3 thread cover seam (narrow or wide). In addition, it has flatlock and rolled hem.
AMBER™ Air S|400
The AMBER™ Air S|400 has 2, 3, 4 thread, plus flatlock and rolled hem. It is very easy to use and thread with its easy jet air threading for the loopers and needle threaders for the needles.
AMBER™ Air S|600
The elite of the elite, the AMBER™ Air S|600 has jet air threading, 2, 3,4 thread overlock and rolled hem. It also has a colour touch screen to help you set up error-free cover seam and chain stitch.
We are happy to take you through a demonstration and advise you better. We have some fantastic offers on at the moment and you can view our range of overlockers on our website here. Why not give us a call on (0115) 9881550 to book your free, no obligation demonstration?
Neil Coles, October 2021