The term "bobbin threader" is used to describe devices that help load thread on an electric sewing machine. Although a traditional bobbin threader was a hand tool made a folded wire loop with a closed end, modern bobbin threaders are more often electric-driven bobbin winders. Such winders feature two opposing posts, one for a full spool of thread and the other for an empty bobbin. By starting the winder mechanism, the posts turn, pulling thread from the main spool and wrapping it around the bobbin. Users control the spinning posts via a push button or foot pedal, depending on the specific mechanism.
A bobbin is a metal or plastic spool resembling a small wheel, around which thread is wrapped for use in electric sewing machines. After it is loaded into a special compartment below the sewing needle, the thread around the bobbin feeds up to the needle to become the underside stitching. Bobbin threader or winder mechanisms serve to load bobbins with thread by spinning from a main spool to the bobbin. Evenly balanced and wound bobbins ensure fewer snags or knots during stitching.
Most modern electric sewing machines feature bobbin threaders, which are also called bobbin winders. Separate machines designed solely to wind bobbins also are available. Whether appearing as part of a sewing machine or as a standalone bobbin winder, each type of bobbin threader serves the same purpose: to wind the thread evenly around the bobbin.
Craftsmen of handmade fly-fishing lures are some of the few people to still use traditional wire-loop bobbin threaders. A fly maker uses a bobbin threader to feed fishing line, string or wire through plastic tubing. Thread is wrapped around the closed wire loop, and then the loop is pushed through the plastic tubing. Hooks are attached to the string, wire or thread and stably secured to the fly via the plastic tubing.