How the Thread goes around the Bobbin Case

How does thread actually go around the bobbin case? It's hard to see all the moving pieces when the hook is installed on the machine, so here's a video with the hook clamped in a vise. (Hook in vise is a vertical axis, rotary hook from a pfaff 545) Vocabulary: hook race gap hook tug hook cast off point Afterwards on a 341 class machine we will show how the cast off point arrives at just the right time to allow the take up lever to pull the thread up and lock the stitch.