Mary handed me a bobbin with a trouble report: it fit into the bobbin holder either way, but would go into the sewing machine either poorly or not at all.
Based on past experience with this lot of bobbins (*), I expected to find a burr inside the steel hub left behind by the saw cut creating the drive dog slot, so this came as a surprise:
A closer look:
That pebble was jammed in place so firmly I needed a pin punch: a small screwdriver wasn’t enough.
It came new from the factory like that, which makes one wonder just exactly what the factory floor looks like.
More likely, the bobbins spend their last few hours in a vibratory polisher and that little rock just crept with all the walnut shell kibble.
Works fine now, so we’ll call it a win.
(*) I gave her a lot of 100 to ensure she never had to unload a bobbin to keep her new Juki well-fed.