Indexable countersinks have a tool body that accepts replaceable cutting inserts to form a cutting edge. They create a taper at the top of an existing hole that lets parts such as flat- or oval-head fasteners sit below or flush with the top of the hole. The inserts 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 tool body from the machine. Indexable countersinks require fewer tool changes than solid tools in high-volume metalworking and fabrication applications with high speeds, high feeds, and difficult-to-machine materials.