what is a serger sewing machine

Familiarization with your serger

Familiarize yourself with your machine and its operation as follows:

  • Go through the owners manual for your machine. Learn the controls for your specific model such as stitch length, thread tension, presser foot up/down lever, cutting width control, etc.
  • Learn yourself or get help? – Sergers are more complicated than sewing machines and can be daunting for some people to learn.  Some people have a harder time than others in the beginning, perhaps you should look into a class where you can get hands-on instruction, many local sewing shops or sewing clubs have such classes. Some sewing shops offer free instruction when you buy a machine. There are also serger tutorials available on-line through YouTube and other sites. Seeing a demonstration can make the difference between a frustrating experience and learning quickly.
  • Run the machine with the presser foot up and without fabric and thread to get an idea of how the machine should sound.
  • Practice and test – If this is the first time using your machine, before you do anything serious you should practice. At first it is a good idea to use two layers of light to medium weight cotton or polyester fabric and general purpose serger thread. Set up your machine according to your owners manual. Run some test seams with different stitch lengths and try the different stitches that your machine can make. Keep these test seams, you can use them later to compare with in case you think your machine has a problem.

Parts and controls

Handwheel – The handwheel looks like a large knob on the left hand side of the machine. The handwheel is used to slowly run the machine by hand instead of using the machines motor. This is done to manually position the needle to the up or down position as needed. Most sergers have counterclockwise rotation just like a sewing machine but some older sergers have clockwise rotation. Most machines have an arrow on the hand wheel indicating the direction of rotation, or look in the owners manual.

Tension dials – There is a tension control for each thread. The tension control is used to set the thread tension to achieve a balanced stitch.

Presser foot lever – The presser foot lever raises and lowers the presser foot. Some people leave the presser foot down all of the time and feed the fabric into the machine (under the presser foot) at the start of sewing. Other people prefer to raise the presser foot and position the fabric right at the cutter and then lower the foot before sewing.

Presser foot pressure control – Controls how hard the presser foot is pressing the fabric into contact with the feed dogs. A medium setting is good for most fabric, lighter for thin fabrics and heavier for thicker fabrics or hard to feed fabrics.

Thread tree (Also called a thread stand) – The thread tree extends above the thread cones and the thread goes through the holes in the tree (thread guides) on the way to the machine. Thread cones are used with sergers instead of the small spools of thread that are used on most home sewing machines. The thread comes from the top of the cone and the cone remains stationary (it does not rotate). Some home sergers can also use spools but cones work better.

Needle – The needles are attached to a needle bar that drives them up and down through the fabric. Some home sergers use standard home sewing machine needles, but some use industrial type needles. Always check the owners manual for your model of machine to be sure you are using the correct needle. Using the wrong type of needle can damage your machine.

Needle bar – The needle bar is the part of the machine that moves up and down and holds the needles. A needle lock screw is used to hold the needle into the needle bar. On machines with more than one needle there may be a separate needle locking screw for each needle.

Presser foot – The presser foot is the part of the machine that presses down on the fabric from above and forces the fabric into contact with the feed dogs that are mounted below the needle plate. Most sergers will accept a variety of presser feet such as cording (piping) feet and gathering feet.

Thread guides – The thread guides control the threads on the way to the needles and loopers. Pay close attention to proper threading through the thread guides. Some of the thread guides are stationary (they don’t move), and some thread guides are mounted on the take up levers.

Take up levers – The take up levers pull the thread slightly to tighten each stitch as the machine runs. There are at least two take-up levers, one for the needle threads and another for the looper threads. The looper take up levers have thread guides on them.

Cutter – The cutters are a set of blades that trim the fabric (cut the edge of the fabric) as it goes through the machine. This is done at the same time as the machine is making the overlock stitch. There is an upper cutter and a lower cutter. One of the cutters is softer metal and designed to be more easily replaced, the other cutter is harder metal (carbide) and will last much longer (generally you can go through two or three softer cutters for each harder cutter.

Feed dogs – The feed dogs are moving metal parts with teeth used to pull fabric through the machine. The feed dogs can be the single type like on a sewing machine or on most newer serger models there are two sets of feed dogs, this is called differential feed. With differential feed the front set of feed dogs can run faster or slower than the rear set allowing the machine to cause the fabric to slightly stretch or bunch up for added control.

Needle plate – Most machines have a single needle plate for all stitches but some older machines need to change needle plates to control the width of the stitch and some machines come with several needle plates.

Stitch fingers – The stitch finger (or fingers) are small metal parts that are attached to the needle plate or the presser foot. It is called a stitch finger because it looks like a tiny pointing finger that has its base right beside the needle hole and it points to the back of the machine. The stitch is formed around the stitch finger. When there is fabric running through the machine the stitch is formed around the edge of the fabric and the stitch finger and when the fabric moves through the machine the stitches slide off the stitch finger and remain with the fabric. When there is no fabric running though the machine but the machine is running, the machine will produce stitches (the chain) around the stitch finger. This is quite different from a sewing machine that has no stitch finger and can not produce a stitch unless there is fabric running through the machine. Most four thread / two needle sergers have two stitch fingers, one for each needle.

Wide stitch finger – Some machines have a wide stitch finger that can be removed from the machine for making a narrow rolled hem stitch.

Loopers – The loopers are moving parts of the machine that mount on a shafts that are controlled by a drive mechanism in the machine, they are located below the needle plate and behind the looper cover. The loopers have a tip and an eye for thread like a needle and form the bottom part of the stitch.

Looper threaders – Some machines have a lower looper threading helper that moves into a threading position to aid in threading. Make sure that you return this part to the running position after you thread the machine.

Two thread converter or two thread switch – Some three or four thread machines have a two thread mode. These machines have a built in part that clicks into a two thread setting or an accessory part that must be added for two thread operation.

Stitch width control – This control sets the distance from the cutter to the needle.

Stitch length control – Controls the stitch length.

Differential feed control – On models with differential feed this controls if the front feed dogs are going faster or slower than the rear feed dogs.

Cutter disengagement control – Most machines have a way to disengage the upper cutter if you want to sew fabric with a precut edge. On some machines (like the Brother 1034D ) the upper knife of the cutter acts as a fabric guide when the cutter is disengaged. In this case the stitch width control for the cutter also sets the stitch width when using the cutter as a guide.

Fabric guide – If you are not using the cutter then it is best to use a fabric guide or a presser foot with a built in guide. The fabric guide will help you maintain the desired stitch width. Not all machines come with a guide.

Light – Most machines have a light to illuminate the presser foot area of the machine.

Power switch – This is a simple on-off switch to turn the machine off when not in use.

Foot pedal – This is a speed control pedal that sits on the floor under the sewing table and is connected to the machine by an electric power cord. As you apply pressure on the pedal with your foot the machine will start to run and increase in speed the more pressure that is applied to the pedal.

Knee lifter – Some machines (mostly industrial type machines) have a lever that is controlled by your knee that is used to raise the presser foot. This keeps your hands free to work with the fabric.

How a Serger Works

In this section  we will learn about the loopers, stitch fingers and see how the stitch is formed step by step. You can see the overlock stitch coming from the back of the presser foot, in this case the machine is chaining-off (making the stitch with no fabric).

Needles and Loopers

The loopers have an eye similar to a large needle. To visualize how a serger works think of a machine that braids or chains thread and you will have the general idea.

The needles and loopers are attached to levers that are driven by gears and shafts inside the machine. They are driven in a repeating motion (cyclic motion). As the machine runs the needles and loopers move as follows:

  1. The needles move up and down vertically and take the thread through the fabric on every stitch. When the needles are up they catch the thread from the upper looper. Then the needles go down through the fabric and pass the thread to the lower looper.
  2. The lower looper moves from left to right horizontally and back again, it only moves under the fabric. The tip of the lower looper catches the needle thread when the needles are all the way down and moves to the right to pass the thread to the upper looper.
  3. The upper looper moves diagonally from lower right to upper left and back again, it catches the thread from the lower looper and takes the thread around the edge of the fabric and up to the needles.

Now that we have established how the parts move we can look at the stitch formation in more detail in the next section.

Description of stitch formation

The overlock stitch is a type of chain stitch (looping stitch) made on the edge of the fabric. The stitch is formed in a cycle that repeats itself just like when you braid hair, but the way the braids are made is a little different.

The cycle starts with the needle at its highest position. The upper looper will also be at its highest position and will be positioned right below the needles. The green upper looper thread is going through the eye of the upper looper. You can also see the needle threads are yellow and black.

The stitch is formed in three steps.

  1. As the hand wheel rotates, the needle goes downwards and catches the thread from the upper looper. Then the needle continues downward through the fabric. You see that the needle has already gone between the green upper looper thread and the upper looper (catching the upper looper thread) and is heading down to the fabric.
  1. When the needle gets to its lowest position the tip of the lower looper moves between the needle and the needle threads, catching the needle thread. The lower looper moves from left to right after it has just caught the needle threads.
  1. Next the needle moves up and withdraws from the fabric. At the same time the lower looper moves from left to right. The tip of the upper looper passes between the lower looper and the lower looper thread, catching the lower looper thread.  After catching the lower looper thread the upper looper continues moving upwards and to the left until it is under the needle and in position to start the next cycle.

If there was fabric in the machine one stitch would have now been completed and the handwheel will have made one complete turn. These same three steps are done over and over to form additional stitches.

Chaining off

Due to the chaining action during stitch formation the overlock stitches can be formed with no fabric in the machine. This is different from a regular sewing machine that can’t run without fabric. Forming a chain with no fabric is called “chaining off”. The chain looks like braided thread.

No reverse

Sergers cannot sew in reverse because the overlock stitch cannot be formed in reverse. When operating a serger only turn the handwheel in the forward direction. Since the ends of the seams cannot be secured by backtacking (backtacking would require reverse) other methods are used to secure the ends.