Ever have this happen - just after you have threaded your sewing machine and bobbin in preparation for a new sewing project, you begin to sew on your fabric and for some as yet unexplained reason, the machine thread balls up and jams in a tangled unsightly mess on the underside of the fabric? It can happen with brand new machines as well as long used machines. There can be several reasons for this to happen and yet there may be some simple solutions.
Many sewing machines today have a horizontal thread delivery for the needle thread. Be sure and place the thread spool with its tiny notch on one end (the notch is used to secure the loose thread end when not in use) facing toward the far right side of the spool holder and not facing toward the left side where the thread will be guided off the thread spool into the vertical tension discs and toward the needle. Sometimes this tiny notch will catch the thread causing undue thread tension on the needle thread as it passes through the tension discs. Placing the thread spool with its notch facing toward the right on the horizontal spool pin seems to help the thread guide off the spool without catching in the tiny notch. Place the notched thread spool facing up if a vertical spool pin is used. No defined notch visible? Newer and better quality spool threads no longer have the troublesome notch at one end, instead the beginning thread end is wound into a barely discernible groove around one spool end. Find this small groove and face the spool thread with the groove toward the right when placed on the horizontal spool pin holder or facing up on a vertical spool pin.
Hold onto both the needle thread and the bobbin thread together, giving slight hand tension to gently pull both after the first stitch the machine makes in your fabric and before allowing the machine to stitch further. With the first uptake of the needle, the needle’s thread tail and bobbin tail are drawn down somewhat loosely into the bobbin case and can become tangled and jam if not held onto briefly. Be sure the bobbin thread comes out of the needle plate in the area it is intended to. After winding a new bobbin, it may help to put the bobbin in its bobbin case or mechanism and just raise the machine needle by hand just enough to allow the needle to bring up the bobbin thread to the top of the throat plate. Give the bobbin thread and needle thread together a slight tug so that they both lay out behind of or to the side of the needle. If you have left off the needle throat plate for last (for those machines that allow or require the throat plate to be removed) when placing the throat plate back on the machine, be careful to guide the bobbin thread through the hole or space in the needle throat plate so the bobbin thread along with the needle thread lie on top the plate.
Using the right type and size of sewing machine needle for the chosen fabric helps as well as using a new needle too. Generally, ball-point needles work great for knits and sharp-pointed needles for woven fabrics. Using the smallest size needle that accommodates the thread size that will be used often produces the best stitches that lie equally spaced and evenly on top and bottom of the sewn fabric.
Using the best quality thread is a plus. The bargain-priced threads found piled in sale bins at the fabric store work great for occasional hand sewing but not as well for machine sewing. Lesser quality thread has a tendency to make thread fuzz as it passes through the needle and can accumulate and jam the thread as the machine makes the stitches. Many sewing machine repair folks hate the thought of us using a can of compressed air to blow out fuzz from the tiny spaces of the machine, particularly the newest digital electronic machines, but a spritz or two of compressed air in the vertical thread slots that hold the tension discs and in the bobbin case itself usually can dislodge bits of fuzz from these spaces. Although compressed air is not recommended for the latest machine models the thought is offered for you to consider for older, mechanical machines. Use sparingly and at your discretion.
Some fabrics produce some of their own copious amounts of fuzzy thread lint. Think high-loft fleeces, some synthetic textiles with short fibers or loopy terry cloth like fabrics. It may help to keep a small, soft artist's brush handy to occasionally wipe away some of this type of fabric fuzz from the needle’s throat plate, feed dogs, tension discs and bobbin area.
Any of the above suggestions often help to keep thread jams from occurring. Give some or all a try!
Sew happy, sew well.