Some embroidery threads have a reputation for being difficult to work with. Breakage during stitching is a common problem, and it's tempting to blame the thread. It may be the thread, but a few slight adjustments to your sewing machine can make a big difference. Of course, sewing machines vary, but these handling tips should help you deal with most stitching problems.
First, let's talk about tension. Whenever you try a new thread, check your machine's upper tension by sewing a 3-in.-long row of zigzag stitches on a scrap of the same fabric you plan to embroider, stabilizing and hooping it properly (for details on stabilizing and hooping, see "Machine Embroidery: A Marriage of Fabric and Design" by Lindee Goodall). The correct tension for machine embroidery should be slightly unbalanced, with a tighter bobbin tension, so the needle thread only shows on the surface, pulling slightly to the underside. If the needle thread totally covers the bobbin thread on the wrong side, the needle tension is too loose.
Improperly balanced tensions can also cause "bird-nesting," that pile of looped threads that forms under the fabric. If this happens, check to be sure the thread hasn't slipped out of the take-up lever guide, check for lint between the tension discs, and clean these discs periodically. Sewing at high speeds can sometimes cause loose threads to get caught between the tension discs. Maintain clean upper tension by cutting your thread at the spool, instead of at the needle, when you change colors or complete a stitching sequence, then pull the thread down to remove it. Pulling the thread up can cause frayed ends to catch between the tension discs, possibly producing damage. Since thread continuously passes through the bobbin tension at high speeds, lint can accumulate and cause thread breakage there also, so clean inside and around the bobbin case often.
Next, look at your machine's thread-feeding system. In my experience, there's no other single variable as critical to successful thread handling as the path the thread takes from spool to needle. If the thread is straight and unobstructed in this path, it's less likely to misbehave. If you're having problems, first check the spool pin: Some threads stitch better from a horizontal pin and others from a vertical pin. A horizontal pin may cause thread to spiral as it leaves the end of the spool, causing the thread to twist and possibly snap. With a vertical pin, the thread may slide down the edge of the spool, collect there, and become lodged underneath the end cap. The thread may even backspin, causing loops and uneven tautness. If you can't adjust the position of your spool pin, try a device like CREATIVE FEET Thread Stand, which guides the thread so it unwinds straight and flat to the needle. It is useful when embroidering with metallic threads, but it's also helpful with any sewing and any thread when there's only a small amount left on a spool. This thread is more tightly wound and may kink as it unwinds.
Consider the direction in which the thread winds off the spool as well. For better stitching, cross-wound spools should feed off the top, and straight-wound spools should feed off the side. Also, some threads behave better when they unwind from the back of the spool, others from the front. If you're having difficulty, try removing the thread spool and turn it around, to feed off the other end of the spool.
What about bobbin thread? Bobbin threads especially designed for machine embroidery are strong enough to withstand the stress of high-speed stitching, yet fine enough to keep densely embroidered designs supple. There are several types of bobbin threads, so I suggest keeping a variety of weights on hand because there is no single all-purpose bobbin thread that works equally well with all specialty embroidery threads. Generally speaking, it's best to use a finer bobbin thread than the needle thread for less bulk and smoother finish.
Use the right needle. Fortunately, needle manufacturers have designed needles specifically for embroidery thread, some with specialized eyes that eliminate stripping or splitting of the thread as it passes through them. Machine-embroidery needles have slightly rounded points (light ball points) to avoid damage to rayon threads. Some Embroidery Needles are designed for metallic embroidery thread and have an elongated eye and a special shaft to reduce friction.
Choose the needle size according to the weight of your fabric. An improperly sized needle or an old or nicked needle can cause thread to fray and break. Remember to replace needles often (I change mine after every five hours of sewing time).
You may come across recommendations to use a silicone lubricant, which coats the thread to make it smooth and flexible, reducing friction and fraying and helping the thread glide easily through the needle. These products can work well, but before using any of them, be sure to check your machine manual. Some manufacturers clearly state that lubricants should not be used on the thread with their machines.
The BROTHER, BABY LOCK and SINGER machines have a “pre-tensioner” which requires non-lubricated thread to pass through the tension assembly, to work satisfactorily. Hoop It All has invented a device to lubricate the thread after the tension assembly. It is called LUBE A THREAD. It is about ½ inch” and is applied after the tension discs and has about 1 drop of “LUBE IT ALL” Silicone Lubricant per hour applied to it.