Different from a tap and die set to cut new threads a thread chaser set is designed for cleaning up and restoring existing threads. They remove dirt and corrosion from threads without shaving off metal and aim to eliminate resistance when reinstalling and removing the bolt and avoid cross-threading.
To use a thread chaser, simply fasten it on a threaded hole or bolt as you would with regular bolts or nuts. Then, turn the chaser slowly down the gunky or slightly damaged threads. Be gentle to avoid causing more damage.
A thread chaser set is for anyone who takes things apart and reassembles them. But most importantly, it is a must-have kit for any auto mechanic for chasing threads on rusty fasteners and bolt holes on cylinder heads, engine blocks, and bodies of vehicles.