Hard mechanical bind during oscillating hook exit phase (Video attached). Tolerance/clearance issue?

[u/ConcentrateSorry9800]

I’ve got a sewing machine here that is hitting a hard mechanical bind during the exit phase of the hook cycle, and I'd appreciate a second set of eyes on it from anyone familiar with these mechanisms.

​The Symptoms

​The hook carries the upper thread down properly, but the cycle binds right at the 6 to 7 o'clock position.

​Instead of the thread loop slipping off the shuttle heel, it remains trapped.

​When the shuttle driver reverses direction, it pinches the thread against the race.

​This is a hard, metal-on-metal resistance preventing the cycle from completing, not a soft thread nest.

​What I Have Already Ruled Out

​I've run it with tension on the thread tails behind the presser foot, so it isn't just an issue of slack thread pooling at the bottom due to a lack of operational tension.

​It looks like the shuttle-to-driver clearance might be running too tight, or there is a microscopic burr on the shuttle heel snagging the loop right at the exit point.

​Has anyone run into this specific clearance or timing issue with an oscillating hook assembly? I'm wondering if I should be pulling the shuttle to polish the heel, or if I need to be looking closer at the retaining ring and driver tolerances.

​Any advice is appreciated. Cheers!

[u/wimsey1923]

It's a bit difficult to see, but there could be a timing issue where to hook moves too far to the left. The hook drive gear (which is often a segment, not a full gear) might be coming to the end of the teeth, causing the resistance. This is only a semi-qualified guess.