Thread Restorer

A thread restorer is a tool used to repair the damaged screw threads on a nut or bolt rather than replace the fastener outright. One common form is a thread restoring file, a hand file shaped to re-cut a worn or corroded thread by hand. Other forms include a chaser tap or chaser die, which is run over an existing thread to clean it out rather than cut a fresh one. Machinists and mechanics use thread restorers on general fasteners, and auto mechanics use chasers specifically on spark plug threads to clear away corrosion and carbon buildup before reinstalling a plug. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/