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Overlock Choices and Options

The choices among models and options on sergers are complex. The obvious choice would seem to be the one that does the most. Unfortunately, sergers are not that simple.

Each type and each brand has its own set of strong points and problems. A good method for deciding which will be best for you is to make a list of all the possible ways you can foresee utilizing a serger. Then give priority to the options you will need the most.

Here is a list of the most common choices and a few of their attributes:

Three-thread machines. This basic overlock has two looper threads with a single needle thread that holds the looper threads in place ( Fig. 7.1). The width of the stitch can range from the narrowest rolled hem of 1.5 mm to the widest overcast at 5 mm, the stretchiest of all the con figurations.


7-1 3-thread overlock

Three/two-thread machine. This model can do the same stitch as the standard three-thread, but it has the option of creating a fine soft edge of only two threads ( Fig. 7.2). This is recommended for silk and other fine fabrics. Unfortunately, the mechanism for switching off the upper looper can make the ma chine very temperamental.


7-2 2-thread overlock

Three/four-thread machine. This overlock can add an extra needle and thread along the center of the normal overcast stitch ( Fig. 7.3). This thread acts as a stabilizer for extremely ravelly fabrics like hand wovens and mohair. Also use it when you need to decrease stretch. The medium and widest width changes can be made easily by threading the other needle.


7-3 3/4-thread overlock

Four-thread. This serger has the 3-thread edge with the addition of a chain-stitch seam 1/4” to the left of the overcast needle thread ( Fig. 7.4). The biggest drawback on these models is the awkward way they maneuver around corners when the chain is being used. The chain can only be used on the gentlest of in side curves without jamming or sewing off the edge.


7-4 4-thread overlock

Five-thread. Most of these sergers can use two, three, four, or five threads at a time, the widest variety of options. At first glance, this seems like your best choice, but it’s also the most complicated. For many home sewers these overlocks are so intricate that the struggle and time spent to learn and use them makes them inefficient.

Note: When threading the seam needle on a 5-thread machine, the first few stitches must be turned by hand with the needle entering a scrap of fabric to prevent tangles and breaks. If it enters air only, you may have trouble.

Needles

There are almost as many needle types as there are brands of overlocks. Some machines require special serger needles that are round on the top. They have no flat side to hold the needle in alignment. The many varieties of serger needles have their own specification of overall length and the depth of the scarf. They are usually classified by letters such as DC or BL. Check your manual for which one exactly fits your machine.

Note: If your machine uses a round upper-shank serger needle, you may have a difficult time aligning the eye straight to the front. After placing the needles in their approximate location, put a toothpick or bamboo skewer in the eye and you will be able to see if it’s facing forward ( Fig. 7.5).


7-5 Straightening needle to exact front

Some overlocks can use traditional sewing machine needles, but even these needles have their idiosyncrasies. The European needles have a deeper scarf on the back (see needle information in Part I) and cause skips on machines set up for inexpensive Asian needles. If you use a traditional needle without the indentation on a machine set up for a scarf needle, it will co too close to the looper and could nick it.

Even within the same needle brand, changes have occurred over the years. When buying needles, have your date of purchase and serial number of your serger with you to make sure you buy the right needle.

You will be delighted to know I am not going to nag you about changing your needle every time you use it. Because the serger thread doesn’t slide back and forth through the eye of the needle, you can use it for eight to ten garments before changing the needle. Even so, if the overlock begins to skip, first try changing the needle.

The size of the needle is also not as crucial in an overlock as it’s in a traditional machine. The majority of your sewing can be done with a 75/11 or 80/12, a rare 60/8 (remember to use fine thread), and an even rarer 90/14 for heavy fabrics.

On a machine with two or more needles, the needles are set at slightly different heights ( Fig. 7.6). This may look wrong to you, but they are in the correct configuration. Check your manual to be sure that the right needle is supposed to be lower than the left on a 2-thread serger. The height difference is due to the rising arc of the up per looper as it comes up and over the fabric.


7-6 Righthand needle is lower, due to arc

Overlocks handle knit fabric with ease. They rarely skip stitches, no matter how tricky the fabric. This is a good thing because ballpoint needles should not be used on sergers. The full round tip can graze and damage a looper.

Stitch-Length Settings

The stitch length of a standard overcast is usually given in millimeters between stitches, one (1) being the shortest and five (5) being the longest. Three (3) is the average and the setting most often used. The shortest stitch length would create a satin stitch much like a traditional machine. Some sergers don’t have a numbered stitch-length dial, which makes them difficult to ad just accurately.

If you were working on an extremely thick or spongy piece of fabric, you might need a different stitch length. Don’t forget, even though you set a stitch length, you are really only setting the amount of push the feed dogs will exert on the fabric. A thick piece of fabric may have difficulty traveling under the foot. Even though the feed dogs push with the same force as on a thinner piece, they can’t move the thick fabric quite as well. It’s like driving your car. You push the gas pedal down to a certain level to go 35 mph on a flat road, but as you go uphill, you will drop back to 20 mph if you don’t increase the gas. Likewise, overlocks require a longer or shorter length setting to achieve the same measured distance.

Differential Feed

In addition to needles and numbers of threads, you must consider an optional feature called “differential feed.” These sergers have two sets of feed dogs that function independently of each other. One set is toward the front of the foot and one set is near the back. By adjusting the rate of movement, the rear set spits the fabric out the back slower than the front pulls it into the machine ( Fig. 7.7). The differential feed reduces the stretch and distortion of the fabric, which is important on many knits.


7-7 Differential feed, side view

Pressure Regulator

The pressure regulator is on the top left portion of the machine. This screw adjusts the amount of push the foot exerts on the fabric. Unfortunately, most manuals don’t even name this crucial part, let alone give you instructions for its use. This adjuster, when properly used, makes the differential feed almost unnecessary.

When the foot presses hard on certain types of fabric, like sweater knits, the fabric will flatten out of shape. Then the machine stay-stitches the stretched edge in place. The overlocked edge will be wavy and permanently out of shape ( Fig. 7.8).


7-8 Adjust pressure regulator to find proper setting

If you keep turning the presser foot adjuster to the left (counterclockwise), the knob will actually fall off in your hand. Put it back on the serger and give it one full turn to the right. This setting exerts the minimum amount of pres sure on the fabric needed to create a stitch. This is the setting for soft, squishy, and stretchy fabrics. If you were working on a sweater knit, this minimum setting would be the correct pressure setting.

As you turn the knob to the right, the pressure increases on the fabric. The thinner or slicker the fabric, the more push the foot needs to exert on the fabric to keep it from wiggling.

Take the time to practice and experiment with this vital adjustment. Once you master the proper setting for your projects, your overcast edges will be perfect.

Specialized Feet

Several specialized feet come with a serger or are available as options:

1. Rolled Hem Foot—Many sergers require a specific foot to do a tiny rolled hem. These feet hold the fabric firmly to obtain the best stitch.

2. Elastic Application Foot—Several brands make a special foot for the application of elastic on the very edge of the fabric ( Fig. 7.9). These feet have a screw on the top to regulate the degree of pucker. For example, you want more pucker under the seat on a leotard com pared to the front of the leg.


7-9 Elastic foot

3. Stabilizer Guide Foot—This foot has holes through it that act as a guide for sewing cord or twill tape under or into the serger seam ( Fig. 7.10). This foot is a standard feature on some machines. On others it can be purchased separately (see your dealer).


7-10 Stabilizer guide foot

4. Swing-Away Foot—This foot helps make the threading easier. The ability to fit your finger close to the needle really helps.

5. Blind-Hem Foot—The serger does a very good blind hem on knits. The hem of knit tops sewn on a traditional sewing machine or by hand will usually break when stretched. The overlock creates a soft stretchable hem that holds up very well on knit fabrics. The foot made for blind hemming serves the same function as a blind-hem foot on a traditional sewing ma chine ( Fig. 7.11). It has an adjustable guide that slides against the same type of blind-hem fold.


7-11 Blind-hem foot

Unfortunately the serger blind hem isn't acceptable on woven fabric. The stitches are too close together and have too many threads to be invisible. Stick to your traditional methods on wovens.

Optional Attachments

In addition to feet, several other optional attachments are available:

1. Containers for the Trimmings-a— Because of the cutting action of the serger, there seems to be a never-ending trail of fabric, threads, and fuzz. To catch these droppings, baskets, cups, or boxes are available, depending on your brand or model. Some machines come with these containers attached and others can be purchased separately ( Fig. 7.12).


7-12 Trimming container

If you have had your serger for a while, contact your dealer. Several brands now have this feature as an add-on item.

2. Threaders—The lower looper is especially difficult to thread. Several brands come with a threader, but most are not very durable. Check with your dealer or look in a sewing notion catalogue for new, longer, stronger, thinner threaders. These have a fine loop on the end and a very long wire to feed easily through the machine ( Fig. 7.13).


7-13 Looper and needle threaders

3. Thread Guides—When you want to use a special fiber or a stabilizer thread, a separate thread stand is helpful. The stand has a tall pole that holds and guides or a clip that's attached to the standard pole as an extra thread guide ( Fig. 7.14).


7-14 Auxiliary spool and feed

4. Thread Nets—These small flexible plastic nets keep slippery thread feeding evenly off the cone or spool ( Fig. 7.15). The net fits over the entire cone and the thread comes easily out of the top.


7-15 Plastic net allows thread to feed evenly off spool

Set Screws

Many overlocks have set screws for adjusting the cutting-blade position and stitch width. A pair of set screws anchors a shaft that passes throughout the machine to keep it from sliding or rotating by piercing it along the side. You will see them as a set of two identical screws close together. Loosen them both before making any changes.

When inserting the set screws, tighten one side slightly, then the other, alternating until they are both snug. If you completely tighten one side, then the other, it will wedge the shaft in crooked, possibly jamming the whole machine.

Looper Threaders

On most overlock brands, the lower looper is the most difficult to thread. Many of them come with a special looper threader ( Fig. 7.16). Because of the tiny hole they must slide through, the threaders are made of fine wire and break easily. If you find one that works for you, buy several. I get better results by stuffing the thread through the hole in the end of the looper and catching it on the other side with the tweezers.


7-16 Lower looper threading methods

Look for the snap-in thread guides. Insert thread as if you were flossing teeth: hold thread on either side and snap into the snap-in guide. These thread carriers are excellent on fixed and minimally moving areas. When the machine is moving rapidly, the thread can work its way out of the loopers with this type of guide and you may get a jam. If the problem is severe, it can be adjusted. Check with your dealer.

Tools

Screwdrivers

Two screwdrivers are generally included with your attachments. The primary use of the large screwdriver is to change the throat plate. Some brands also use a big screwdriver for adjusting the fixed cutter position, stitch length, and other adjustments.

Screwdrivers are meant to be used with two hands. You push down with one hand and rotate with the other. That way you won’t scab the top of the screws. See Fig. 2.2.

Use the small screwdriver to change the needles. The needle screws should be barely loosened while holding onto the needles. The needles drop out easily and tend to fall inside the machine when not grasped firmly. If there are two needles, don’t loosen the needle clamp screw too far or it will be difficult to feel the groove inside the needle shaft.

Tweezers

Tweezers will rapidly become your best friend when working on an overlock. I use them when threading the needle as well as the looper. I own several tweezers and keep one inside the body of the machine for easy accessibility. Tweezers must come together cleanly at the tips and have no snags. Smooth the tips of your tweezers regularly by rubbing them with crocus cloth.

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Wednesday, 2009-04-29 13:02