What is a serger?
Sergers and overlock machines are a special type of sewing machine that makes an overlock stitch. The overlock stitch is a stitch specifically designed for use in edge finishing, hemming and seaming. Edge finishing is sewing over the edge of the fabric to prevent the fabric from fraying. The overlock stitch can only be made on the edge of the fabric because the stitch actually wraps around the edge of the fabric.
A serger does not replace a sewing machine, it is best used along side a sewing machine. A serger can do a much better job of edge finishing then a sewing machine can, but you will still need a sewing machine to do straight stitches and zigzag stitches.
In contrast to a serger, a regular sewing machine makes a lockstitch or a zigzag stitch.
While a regular sewing machine can be used for edge finishing with a zigzag stitch, a serger does a much better job. Sergers are also faster than sewing machines. Some sewing machines have a modified zigzag stitch that they call an overcasting stitch, but this stitch is not much better than a zigzag stitch for edge finishing and nowhere near as good as a true overlock stitch made by a serger.
The overlock stitch is made using a needle on the top side of the fabric and parts called loopers on the bottom side of the fabric. This is instead of the needle and rotating hook used in a regular sewing machine. The loopers in a serger are mounted below the needle plate in the same area you would find the hook and bobbin in a regular sewing machine.
Sergers can only sew on the edge of the fabric because the upper looper travels around the edge of the fabric on every stitch. If you tried to sew in the center of the fabric with a serger the upper looper would tear through the fabric. Because sergers only sew on the edge of the fabric they don’t need a big harp space (clearance from the body of the machine to the needle), that is why sergers look squat and are very compact. Even though sergers can’t sew in the center of the fabric, sergers can make construction seams by joining the edges of two pieces of fabric
When sewing garments the overlock stitch is usually positioned on the backside of the fabric where it will not be seen. If a decorative appearance is desired similar to a coverstitch, a regular sewing machine can be used to secure the edge of the overlock seam to the front side of the fabric. A four thread overlock stitch is sewn flat to the fabric with a straight stitch from a regular sewing machine. The stitch from the sewing machine is the black stitch directly below the yellow stitch that is part of the overlock stitch.
In addition to making the overlock stitch, sergers have a cutter to trim the edge of the fabric while the fabric is going through the machine. The upper cutter blade to the right side of the presser foot is trimming the edge of the fabric and the trimmed fabric is falling away. The cutter can be disengaged if you do not want to trim the fabric while the overlock stitch is being made.
Technically speaking sergers have a cutter and overlock machines do not have a cutter, but in common usage the term “serger” and “overlock machine” are interchangeable and mean the same thing. Also most sergers are able to disengage the cutter if you have precut fabric and don’t want to trim the edge of the fabric as it is going through the machine.
Types of stitches and sergers
The fabric is folded over so you can see both the front and back sides of the stitch. The front side and back sides of the stitch are similar but not exactly the same.
- 3 thread machines – have one needle and two loopers and can make the three thread overlock stitch. The three thread overlock stitch is good for edge finishing, flatlock, decoration and non-structural seams but not for construction seams, because it lacks the strength needed for construction seams. A structural seam (or construction seam) is a seam that is subjected to stress, in other words any seam that holds something together. A non-structural seam is used for edge finishing or for decoration and does not get stressed, an example would be a hem of a dress or the edge of a blanket.
- 4 thread machines – have two needles and two loopers and can make both the three thread overlock stitch and the four thread overlock stitch. One needle is removed to make the three thread stitch. The four thread overlock stitch can be used for construction seams and for decoration because the fourth thread makes the stitch much stronger than the three thread stitch. The four thread machines are the most popular type of machines.
- 5 thread machines – have two needles and three loopers and make the five thread safety stitch that is actually a combination of the three thread overlock stitch and a two thread chain stitch. The five thread safety stitch is used for construction seams. The five thread safety stitch can be stronger than the four thread overlock stitch and is usually wider. Most five thread machines are designed to make a wider stitch than a four thread machine. Five thread machines are often used for construction seams on heavier fabric like denim.
The two thread overlock stitch is used for flatlocking, edge finishing and decoration. Some three, four and five thread machines can be set up to make the two thread overlock stitch. Although they are rare, there are also two thread machines that have one needle and two loopers and only make the two thread overlock stitch.
When describing machines, a machine that can make a four thread stitch and a three thread stitch is described and a 3/4 thread serger. A machine that can make a five thread stitch, four thread stitch, three thread stitch and a two thread stitch is described as a 2/3/4/5 machine.
For general use a 3/4 thread (2 needle) serger is the best compromise between function, complexity and cost for the following reasons:
- A four thread stitch is strong enough for most applications. A five thread machine is more expensive and complex so unless you really need five threads a four thread machine is the way to go.
- There are very few three thread (1 needle) sergers still being made because most four thread sergers will also make the three thread stitches by removing one of the needles, so it really makes more sense to buy a four thread machine.
- Do you need two thread stitches? – Probably not. For most uses a three thread stitch can be adjusted to have a similar look and function and a two thread stitch is not required.
Home sergers are also called domestic sergers. The reason they are called “home” or “domestic” is because they are designed to be used at home and not in a factory (Industrial overlock machines are designed for use in factories). Home machines are smaller and relatively light weight when compared to industrial machines. Some home machines can weigh as little as 12 pounds. Sometimes home machines are used for small business when small size and portability are needed. They are also used in schools and for sewing classes.
The characteristics of home sergers:
- Flexibility – Home sergers are flexible and can be used for many types of sewing such as making clothing, quilts, blankets, curtains, light upholstery, etc. Home sergers can sew materials from light weight to medium-heavy weight. Several types of presser feet are available for most home machines including general purpose feet, elastic feet, piping (cording) feet and shirring/gathering feet. Some home sergers have free arms for stitching around sleeves, pants cuffs and other cylindrical patterns.
- Needles – Most modern home sergers use 130/705H type needles, this is the same type of needle that is used by modern home sewing machines. Some older home sergers use a different needle type so always consult your owners manual for your specific machine to be sure. Most home sergers are designed for needle sizes 11 to 14
- Portability – Home sergers are small and portable and some come with cases or built-in carrying handles.
- Speed – Typical maximum speeds are from 1300 SPM (stitches per minute) to 1500 SPM depending on the model. This speed range is well suited to home sewing and allows good control of the machine. For most home sewing you would not want a faster machine because it would be hard to control. In contrast most industrial machines run at much higher speeds for repetitive factory sewing.
- Reliability – Home machines can be very reliable and can last for many years, but they are not designed for continuous use (like in a clothing factory). They lack a forced oil lubrication system that most industrial machines have so if you were to use a home machine in a factory it would need to be manually oiled every week.
- Motors – Home machines have built in motors that are controlled by a variable speed foot pedal. They can run at low speeds when needed.
- Thread type – Home machines can use a wide variety of threads from light weight to medium weight.
- Cost – Prices for new home machines start at $180 for inexpensive models and go to more than $3000 for fancy machines. Used machines start at under $100.
Industrial overlock machines
Industrial machines are designed for continuous use in factories. Sometimes they are also used in small business and by home sewers when extra durability or speed is needed. Most industrial machines do not have built-in motors like a home machine, they use large motors that mount under a specially made table. The foot pedals below the table are used to control the operation of the machine leaving the hands of the operator free to guide the fabric.
The characteristics of industrial overlock machines:
- Flexibility – Industrial machines are more specialized than home machines. If you are buying an industrial machine make sure that the model you choose is compatible with the type of tasks you will be doing and that any feet needed are available for the machine. Some industrial machines are set up for light weight fabrics and high speed operation, these models can not be adjusted for use with heavy fabric, so pay close attention to make sure you get a machine that meets your requirements. Industrial machines have larger beds then home machines, this allows for sewing larger items.
- Needles – Industrial machines use special needle systems that are not interchangeable with other machines.
- Portability and Size – Industrial machines are generally not portable. The combination of machine, table and motor usually weigh from 150 to 250 pounds.
- Speed – Most industrial machines are set up for rapid start/stop operation at high speeds of from 4000 SPM (stitches per minute) to 8000 SPM. Stronger precision balanced parts are used to withstand these speeds and run with less vibration. Heavy-duty models (for heavy weight fabrics) are generally slower.
- Reliability – Most industrial machines have a forced oil lubrication system with an oil pump and oil reservoir. The lubrication system allows reliable operation when the machine is used for many hours a day at high speeds.
- Motor – Most industrial machines have large motors that mount under a specially made table and connect to the machine with a drive belt. Some newer industrial machines have direct drive motors built in to the machine (no motor under the table, no belt to adjust). With a standard clutch motor industrial machines are not very controllable at low speeds. For for precision sewing at low speeds a special type of servo motor (computer controlled motor) is needed that has been optimized for low speed control. These motors are now available for under $200.
- Stitch Types – Most industrial machines are set up for one stitch type only, however there are a few models that can sew several stitch types.
- Thread Type – Most (but not all) industrial machines are set up for a limited range of thread sizes and types and must be readjusted to use a different thread sizes or types.
- Cost – Industrial machines are not prohibitively expensive. Prices for new industrial machines start at about $950 for a complete machine (with motor and table) and go to more than $10,000 for automated CNC (computer numerically controlled) machines. Used Industrial machines start at around $300
Specialized machines are truly “one trick ponies” and usually do only one thing, but they do that one thing very well and very fast. Some examples of specialized machines are hemming machines (for hemming) and cover stitch machines (makes a covered seam used in certain types of clothing). Specialized machines are not adaptable or configurable. Most specialized machines are industrial although there are a few specialized home machines such as coverstitch machines and blind hem machines.