A couple of weeks ago Iceblossom noted over here
Help Appreciated. Japanese Machine troubleshooting
about believing in replacing needles often, and I didn't think much of it.
The last week or so I'd been cleaning up a barn find 15 clone
Barn Find
And was running into some troubles. I couldn't get the lower main shaft to spin freely and based on the rusty oil dripping out of the oil holes assumed there was significant rust binding things up that I couldn't get to. Finally I looked at the bobbin end of the shaft and found that the part noted by the arrow had been bent and was scraping against the fixed housing during the stitch cycle. Once I bent enough in the other direction things started moving. I put it all back together, using a new needle, and tested. There was a lot of noise and scraping sounds, etc. A little more bending here and there, adjusting the housing for the hook, and I still couldn't get it to sew past 2 stitches as the thread kept breaking below the needle plate. I thought the timing might be off and must have hand turned a couple of hundred stitches watching the hook work properly, and then watching the thread break.
After about 5 hours of this I was ready to consign the completely intact machine to "parts" status, and then Iceblossom's words rang in my ear: I believe in replacing needles often. I did just that, getting a needle from a different container this time, and I sewed stitches until I ran out of thread. Hopefully this is something I won't forget soon.