The 01-8400-0-000 KEY from AMF Reece is a small but crucial mechanical part used in industrial sewing machines. It’s a precision-fit key —a metal shaft with a square cross-section—inserted into mating grooves to lock and align moving parts within the sewing machine's internal drive mechanisms. This ensures components stay properly engaged and synchronized under heavy-duty operation. These keys resist rotation between shafts and hubs, maintain timing, and prevent slippage—vital for consistent stitch quality, especially in high-speed or industrial environments.