Re: busted studs
Try and extract the broken stud with an easy out. Replace with a good m6 stud. If that fails buy a 1/4" x 20 sae tap. An end tap is preferred. Drill out the old threads with the exact size bit that the 1/4" tap calls for. It is important that you drill the exact size hole that the tap calls for and drill as straight as possible to avoid reaming out the hole too much.