Top Thread Frequently Breaks – Kenmore 158.19412
Please help me diagnose and fix my thread breaking problem with my Kenmore 158.19412 sewing machine. I’m trying to sew a face mask with thin cotton fabric. Running a straight stitch at 10-12 stitches/inch over two plies of material. I might be able to sew 1-4 inches before the top thread breaks.
Three observations: 1) sometimes there seems to be too much slack between the thread tension adjustment assembly and the needle which results in thread wrapping around parts of the thread guides 2) sometimes there is extreme resistance going through the tread tension plates in the assembly where there was “proper/expected” tension before starting to stitch. 3) sometimes it seems to be stitching/not breaking but I find that there are gaps where the top thread has not caught the bobbin thread to make a stitch every time.
What I’ve done: 1) gone through adjusting thread tension using two plies of thin/shirt cotton fabric and, separately, two plies of flannel shirt fabric. Tested several settings and at times things look good. 2) cleaned and lightly oiled the moving parts inside the front end 3) disassembled, cleaned and reassembled the tension adjustment assembly per the Stagecoach sewing video on YouTube. 4) replaced the needle in the machine 5) tried several stitching lengths: 8 to 12+ stitches/inch.
Insight as to what’s wrong with a machine that has worked well in the past.