Why is my thread breaking?

May 25, 2014

Few things can be more frustrating than thread that constantly breaks. APQS machines can sew with nearly every type of thread, from 100-weight silk to 12-weight heavy cotton. Successful thread use requires being willing to make adjustments to the tension, both on the top as well as to the bobbin. Don’t worry, we’ll help you figure it out! Here are different causes for thread breakage, along with solutions:

Improper threading

Double check the thread path and ensure the thread isn’t catching on the spool, laser cord, or other obstruction. Re-thread the machine by completely removing the thread from the machine, and then starting over with the cone and first thread guide. Click here for information on threading your machine.

Incorrect or damaged needle

APQS times each machine to an MR 4.0 industrial needle (equivalent to a size 18). This needle has a large eye and can withstand the flexing that happens when you move the machine (over-flexing can cause directional tension changes.) If you use a needle that does not have a large enough eye for the thread thickness or type, the eye will fray or slice the thread. Match the needle size to the thread. For very thin thread, you may switch to an MR 3.5 (size 16), and you can increase the size to an MR 4.5 (20) for heavy, thick thread. Try a new needle if you have trouble with thread breakage and are using the correct size for your project. APQS carries the correct type of needle for your machine in each of these sizes. (We don’t recommend titanium-coated needles.) Call our toll free number at 800.426.7233 to order.

Bad thread

Even if you have completed 1-2 quilts or more with this thread, you can have a bad spot in the cone of thread! Dark thread tends to break more easily than light. The thread’s composition can cause the breakage; cotton, rayon, some trilobal polyester and other weaker fiber threads tend to break or fray more frequently. To eliminate the thread as the culprit, put a new cone of thread on the machine. if the thread doesn’t break, then there was something wrong with your first cone.

Old Thread

Yes, thread can have a shelf life (especially natural fiber thread). It loses its moisture content over time and becomes weak and brittle. You may be able to sew with it by “re-hydrating” it with mists of water or by treating it with a thread lubricant called “Sewer’s Aid” (liquid silicone), available in the notionsdepartment at many sewing centers. However, the best solution may be to start with a fresh spool. To increase your thread’s shelf life, store it in a closed container away from direct light, where sunlight and UV rays can not accelerate the damage.

Upper tension is too tight

If your top thread is already at its peak stress level as it passes through the tension assembly, it is bound to break. Try loosening the top tension knob a LOT, even if it means that your tension disks don’t touch each other. Remove all the top thread pressure to eliminate tension as the problem and “start over”. If the machine sews with no tension on the thread, start turning the tension knob tighter (clockwise) while testing your stitches. Continue to adjust until the stitches appear normal again. NOTE: You may need to loosen the bobbin tension at the same time so that the bobbin thread doesn’t pull the top thread to the back of the quilt.

Bobbin tension is too tight

If the top thread breaks, it doesn’t seem logical that you would consider the bobbin tension as a possible reason. However, the bobbin thread content as well as the tension setting can cause the top thread to break. For example, most pre-wound bobbins are made from polyester thread. If you are trying to use cotton thread in the top with that pre-wound bobbin, the bobbin’s strength may cause the top thread to snap. Loosen the bobbin tension (don’t be afraid to loosen it considerably–even if it makes you uncomfortable) and test your stitches until you get a balanced stitch with no thread breakage.

Burrs on the hook assembly

Burrs on the hook assembly are caused by needle strikes. You don’t have to break a needle to develop a burr on the hook. Just hitting a bulky seam can deflect the needle enough to strike the hook as it rotates, putting a scratch or burr on the metal. Since the top thread travels completely around the hook to form the stitch, it will find those burrs and break. Use the appendix in your User Manual (located on the companion CD that accompanied your machine) titled “Hook Maintenance” to help locate the common areas for burrs, or click here to view the document. If you find one, rotate the assembly by turning the fly wheel by hand until the burr faces the floor. Then use fine, 400-grit emery cloth (found in the hardware or automotive store) to smooth out the rough spot.

Burrs on the needle plate

Just as your hook assembly can suffer from broken needles or “near misses”, so can the needle plate hole. Your top thread travels all around the inside of that hole as you sew. If a needle has scratched the hole, the scar will cut your thread. Remove the front screw on the needle plate (and the thick and thin washer underneath if you have a thread cutter). Loosen the back screw and rotate the needle plate away from the machine. Tighten the back needle plate screw; this will temporarily hold the plate firmly while you check the needle hole. Drop a length of thread into the needle hole, and “floss” all around the hole to see if the thread catches on a notch or scratch. If you find one, cut a narrow strip of emery cloth (see answer above) and carefully polish out the burr or scratch. Be careful that you don’t enlarge the hole or change its shape by sanding too aggressively.

Notches or burrs in the “pig tail” thread guides

These can develop over time, especially when using coarse threads like metallics and invisible nylon or heavy polyester thread. Replace the pig tails, or for a temporary fix, loosen the screws holding each one in place and rotate the pig tail guide 180 degrees so that a different spot on the guide is being used.

Incorrect thread path for thread type or twist

Most longarm quilters use thread that comes in cones. However, you may find a specialty thread that you’d like to try that comes on a normal small spool. If the thread wraps around the spool in “stacking circles” instead of criss-crossing itself as it wraps around the spool, it will work best mounted horizontally on the machine. This allows the spool to turn to release the thread instead of causing snarls.

APQS offers lifetime customer support! Education Director Dawn Cavanaugh shares lots of tips and information on the APQS blog that may also help you with your thread and tension questions. You can also reach Dawn at  800.426.7233, or email her. We’re here to help!