If you've been working on automobiles for any time at all, you've probably experienced the letdown of stripped and damaged threads. Go to tighten a bolt and there's the sinking feeling of a bolt that won't twist. It pops and just keeps going round and round. Although thread repair or replacement is intimidating for the novice, it doesn't have to be. Be it iron or aluminum, you have choices on how to repair or restore damaged threads in your home garage without having to resort to a machine shop.
Damaged threads are more common with aluminum castings, which have threaded inserts commonly known as Heli-Coils, though there are other types of threaded inserts out there. First, ascertain what has happened to the threads. Sometimes, damaged or stripped threads can be chased with a tap or a thread chaser using machine oil and returned to service. When threads are stripped completely out, they must be replaced with an insert or drilled out to a larger size and tapped for a larger fastener. You can find Heli-Coil and other types of thread repair inserts at any auto parts store, machine shop supply house, or home improvement store.
When holes are properly tapped for Heli-Coil inserts, inserts provide permanent conventional 60-degree screw/bolt threads that will accommodate any standard screw or bolt as long as it is sized properly. Heli-Coil inserts provide tremendous strength once properly installed and won't wear out during repeated fastener removal.