Looping FAQ
Looping and Birdsnesting
Birdsnesting is usually caused by the inability of the top thread to pass
around the bobbin or the lack of control of the top thread. Inability to pass around can be caused by such things as little or no lubrication, or the top thread catches, it can catch on a damaged part, a sensor that is damaged or out of position, it can catch on a positioning finger that is incorrectly set or damaged, a hook that is damaged with either visible damage or damage between the hook and the bobbincase basket, it can catch on a cracked or damaged needle plate too. The thread can also catch on the goods being sewn if the goods are “pinching” the thread, more about this below.
Lack of control can range from too little tension on the top thread to pull up a stitch, not threaded correctly or improper take up spring adjustment.
Looping can be caused by all of the above too. A birdsnest is a form of looping, the first stitch gets caught somewhere in the path below the needle plate, the stitch is not pulled up correctly and the “loop” is caught. The next stitch can’t pass around the bobbincase because the first is still stuck in there, so on and so on, until you have a “nest”.
Looping, when caused by the above problems is a birdnest that didn’t get going completely, the first stitch did get pulled up, though not correctly.
Looping can also be caused by thread stretching. Polyester thread is not as elastic as rayon, when it stretches as the stitch is formed, it may not return to it’s original length. Increased “spring” on the take up spring often helps reduce this problem. A good brand of poly can help too. While the increased spring most likely will work fine if you go from poly to rayon, if your machine was originally set with rayon you might need to adjust the take up spring for poly. Once adjusted you should be able to go from poly to rayon without trouble. Again a good brand of poly is essential.
Thread can be pinched by the goods when the diameter of the needle is not sufficient. The needle comes down into the fabric to it’s lowest point, then it rises back up a certain amount. If you look at your needle you will see a long groove going down the front and a “flat” area on the back above the eye (called the scarf). When the needle comes down to the lowest point the thread lies in the long groove on the front of the needle, the thread is held against the needle on the back by the fabric. the needle rises a bit and a loop of thread is pushed out the back side of the needle, forming a loop from the eye in the scarf area. At this point the hook passes by and enters into the loop. The hook pulls the loop around the bobbincase that is inserted in the hook basket (bobbinbasket). A great deal of thread is pulled off to form the big loop that goes around the bobbincase. The needle rises out of the fabric at the same time as the take up lever and take up spring are doing their parts to pull all that top thread back up into a nice tight stitch (not too tight!). IF the needle did not make a big enough hole in the fabric for the thread to pass freely as the loop is being pulled up, guess what? The loop doesn’t get pulled up all the way! Some fabrics can also grab the thread, cordura (spelled right?), vinyl and other “coated” fabrics are notorious. Wax paper or silicone lubricants often help.
Ball points vs Sharp when looping: remember that a ball separates the fibers and a sharp cuts. If you use a ball on a heavy canvas you may see looping, although I would imagine an 80 to be big enough in most cases, if it is a ball and simply pushing the fibers aside the hole from the needle may not be formed right for the thread to pass freely, maybe a sharp is the answer!
And your design too can cause both looping and birdsnesting. Too many stitches being put into the same area and the machine starts having a hard time pulling up the thread. There are a number of reason we want to avoid tiny stitches in designs, a bit of movement from one stitch to the next is important, not only do you not want to put holes in your goods but when forming a stitch you don’t want to drive the stitch you just completed back into the formation of the next stitch. Too much density or stitches in the same hole must be avoided too!
The bobbin has a little to do with “forming” the stitch. Mostly it just sits there with or without the correct tension, assuming the case is not damaged, it’s threaded right and in properly. The top thread passes around the bobbincase basket, the bobbin thread is being pulled off the bobbin by the top thread forming the stitch and by frame movement (movement of the goods). Erratic bobbin tension can give you birdnesting and looping because the top thread is unable to pull any bobbin thread out as it forms the stitch, leaving the top thread loop caught. Erratic bobbin tension that pulls and releases sporadically can cause you problems with overspin although rare on prewound with sides. I have also seen bobbins that pull and feel fine until you stick them in the case and then in the hook, only then you can feel that it is not pulling right. Erratic bobbin tension can be caused by dirt or lint under the tension spring or a groove worn in the case too. It can also be caused by a poorly wound or overwound bobbin. Or lubrication (get the theme here?) :>)
For birdsnesting/looping I look first at my upper thread path and tension, next bobbin and then needle, on the assumption that I thought I had the correct needle for the job. If I am sewing a fabric that is known to cause problems I may change the order of what I look at. Always assuming I have lubricated my hook as specified by the manufacturer FIRST! Sorry but a lot of looping can be corrected by lubrication. If you don’t lubricate on a
regular schedule you might look there first.
Understanding how a stitch is formed can vastly increase your success when dealing with looping and birdsnesting.