The sewing machine just wouldn’t work anymore )-:

When I was sewing my blouse jacket over the weekend, I had to rewind the bobbin. I did that, put the bobbin back in, and suddenly the sewing machine wouldn’t work right anymore. I didn’t have the patience to figure out what was wrong at that moment, so I just turned off that little pain in the neck, shut it up, and put it away—then I dug out my old little sewing machine, because it’s never let me down in 31 years. So I finished sewing the blouse jacket with that one.
Today I had the time and inclination, so I took a closer look at my little troublemaker; it was clear to me from the stitch pattern that showed up every time I did a test stitch that the problem was with the bobbin thread tension. I gave the machine a thorough cleaning and blew it out, and I also ran an oil-soaked thread through the tension discs to make sure no lint or small threads were caught in there. I reassembled the sewing machine and did a test stitch—again, that annoying clacking sound while sewing, and the bobbin thread looked like anything but the way it should.
 So I checked the sewing machine’s manual again to see what the problem might be, and there I read that these machines tend to act up when the bobbin thread isn’t wound properly or well. But it was—I took a closer look at the bobbin anyway, and lo and behold, I spotted a tiny crack in it that I hadn’t noticed before. So I rewound it onto a new bobbin, took a closer look at the old one again, and sure enough, you can see that it has a tiny little crack on the inside. I immediately did a test stitch with the new bobbin, and lo and behold, it’s working just as it should again :-))) Apparently, the bobbin had suffered from wear and tear, which caused these cracks. I should also mention that I usually use my bobbins until they fall apart, but I’ve never had this happen before. So don’t panic right away just because the bottom seam isn’t looking the way it should but is showing lots of big loops; first clean the machine and check the bobbin.

Best regards, Inge

Thank you so much, dear Inge, for this post. It’s amazing what an impact a barely visible crack in the bobbin can have. I wouldn’t have thought so at all. Sensitive machines show this; sturdier models might be able to handle it.

In this case, you solved the problem—great! And you went ahead and thoroughly cleaned and oiled the sewing machine right away. Now it shouldn’t act up anymore, and the old machine can take a break again. It’s also nice to see that a 31-year-old sewing machine is still in tip-top working order.

Have a lovely afternoon and treat yourself to something nice.
Warm regards, Ina