Insert taps cut the oversized special thread needed for thread inserts (e.g. Helicoil wire inserts, key-locking inserts), with a larger pitch diameter to house the insert. Common in aluminum/magnesium or for repairing stripped threads and boosting thread strength and wear resistance—after installing the insert you get a standard, high-strength thread. Used with matching inserts and tools. Mainly HSS. Select by insert brand, thread spec and hole type, and set tap-drill and depth per the standard.