Spark plugs that haven't been changed for a long time can become one with the cylinder head. Fortunately, it's possible to repair damaged threads instead of scrapping the head. (Photograph by Chris ...

We have all done it, overtightened a bolt and blown out the threads. When a bolt starts to tighten up and then go suddenly loose, you know that the threads are toast and now you have a problem.

1) Start by drilling out the damaged threads. If possible, use a drill press to make sure you get a straight hole. Otherwise, do everything you can to ensure the hole drills straight. If the hole is ...