Indexable thread-turning inserts are used with lathes or CNC turning machines as part of a modular thread-turning tool system to cut threads on a workpiece. Each threading insert is designed to cut either internal or external threads to a specific thread standard. These replaceable on-edge or laydown inserts mount to a compatible thread-cutting head, which connects to a quick-change toolholder. The inserts typically have multiple cutting edges so they can be rotated (indexed) to expose a fresh cutting edge when the old one dulls. They can be replaced with new inserts of the same type or different types without removing the toolholder or tool body from the machine. Indexable threading tools require fewer tool changes than solid tools in high-volume metalworking and fabrication applications with high speeds, high feeds, and difficult-to-machine materials.