A high-quality sewing machine should last for many years before it needs repairs of any sort, but even the best machine can fail to work properly on occasion. Very often it's user error that causes such problems, and a few quick fixes on your part can get the machine working again. Note a few troubleshooting tips you'll want to consider for your sewing machine when it starts giving you issues so you can get sewing again in no time.
One very common reason for thread to break while you're sewing with a machine is that you're using thread that is actually meant for hand sewing. Thread meant for machines is thick and tough, and better able to withstand the stress of the machine's increased speed and pull. Along with ensuring you're using thread for a machine, be sure you're using thread thick enough for the material you're sewing; thin thread is meant for thin fabrics, so it may break even if the thread is meant for use in a machine.
Fabric doesn't feed
A sewing machine may not feed fabric if the foot is not lowered, as this is a safety mechanism against getting your fingers too close to the needle, so check the foot's lever and ensure it's in the engaged position if your fabric doesn't feed. Also, a machine may sense if a stitch doesn't go all the way through the fabric and will stop feeding that fabric. Check the stitch length you're using and adjust it as needed. You might also be trying to force the fabric through the machine too quickly, and this can cause the stitch to jam, and the fabric won't feed. Let the machine feed the fabric as needed and it won't jam as easily.
Uneven or skipped stitches
If stitches are coming out uneven, or being skipped altogether, this is often due to a broken or bent needle. If the needle is broken, it won't catch the fabric with each stitch. If the needle is bent, the stitches will be sewn haphazardly. The needle may also not be sitting in the machine properly, so that it doesn't catch the fabric with each stitch as it should. If this happens often, even after changing needles, consider if you're trying to sew fabric that is too thick for the machine, or for the size of needle you're using. You may need to get a piece sewn by a professional if it's too thick for your own machine and keeps damaging the needles you're using.
For more tips, contact a company that does sewing machine repairs.