The tools needed to repair a Singer sewing machine include sewing machine oil, a screwdriver, and a brush or a soft cloth, preferably chamois or microfiber. A thorough repair also requires extra thread and scrap fabric to test the machine's tension.
To repair a Singer sewing machine, first unplug the machine, and remove all visible screws with a screwdriver. Take the case off, and inspects the gears. Lint and debris interfere with smooth sewing, and a small brush or cloth can be used to remove it. Most machines come with soft, narrow brushes for this purpose. The moving parts should be cleaned with a cloth soaked in lubricant. Then, the moving parts should be oiled with sewing machine oil.
Reassemble the machine and test it on scrap fabric to remove traces of oil and examine the stitches. The stitches should be equally even on the top and back of the fabric. Loose or overly tight threads are remedied by adjusting the tension knob on the front of the machine.
Common sources of sewing problems include inappropriate thread and misthreaded bobbins. It is important that the bobbin and main threads are of good quality and equal weight.