Sewing machine stitch formation lockstitch

 I wrote this description of how a sewing machine forms the lockstitch, for a response to someone needing help with extra threads, coming out of their bobbin area, when sewing. It received a lot of positive response, so I want to share it here, as well, so it can help other peoplefix the "extra threads" mystery.

Complete the stitch before removing your project. Just like hand sewing, the stitch is not completed, until the takeup lever pulls the stitch tight, which is when the takeup lever, and needle, are at their highest point.

Otherwise, those "extra threads", are actually your needle thread, as it encircles the bobbin case, in order to form the loop under the bobbin thread. The upper thread "lassos" the bobbin thread, by throwing a loop around the bobbin case, then the takeup arm playing the cowboy, pulls the loop closed, creating a lockstitch!