If you love to sew and have invested in a good sewing machine, it should last for many years without any problems. However, if you're not using it properly or have neglected its maintenance, it can soon start to act up. This is true of a machine you use at home or a commercial machine used to sew garments, to stitch shipping bags, and the like. Note a few quick troubleshooting tips for very common sewing machine problems.
Thread looping under the fabric
This is often the cause of not enough top tension in the stitch; when you don't have enough tension, the needle won't pull the thread through enough as it comes up from under the fabric. In turn, the thread will form a loop. Check the bobbin tension and the top tension of the machine and be sure they're both set to a medium setting; you might even increase the tension if a medium setting doesn't correct the problem.
Fabric won't feed
First be sure you're not trying to push the fabric through faster than the machine allows, given the type of stitch you're using. It may be feeding but simply not fast enough to suit you, but is the speed needed for the needle to work.
If the fabric won't feed at all, note if lint has built up in the feed dogs. These are like a set of teeth that are in the plate of the sewing face on the sewing machine. They need to be up and free of debris for them to feed the fabric through. Some machines allow these feed dogs to be set down so you can guide the fabric by hand, so note if your machine has this setting and if the feed dogs are down; if so, the fabric won't feed automatically.
Machine suddenly stops
Many sewing machines, whether they're for commercial or private use, have an automatic shutoff feature for when the motor gets too hot. If you've been running your machine continuously for some time, note if the motor casing feels warm to the touch. If so, the machine may have simply shut itself off. Let it cool down for several minutes, even half an hour, and try starting it again. If this corrects the problem, you may need to see about keeping the motor cooler during constant use; set up a fan that directs air away from the machine to vent it or stop using it after a certain amount of time so the motor can cool down as needed.