Mechanic or machinist?
Thread repair is not typically within the realm of common repairs for an auto mechanic. I mean, obviously we all need to know how to handle it as my mentor stated, but it’s difficult knowledge to acquire. Factory manuals don’t cover it. Most technical schools don’t, either. Nor is thread creation and repair really the focus of most adult education courses like welding or machining.
Threading operations are often the domain of the tool and die maker, a dying trade in this country. It’s related to machining, but it’s focused on creating tooling in a toolroom rather than production. Unfortunately, thread repair, especially on an item that is in situ, can be especially difficult, and most machining texts don’t account for poor tool access.
Many mechanics are not well-versed in threading operations for the same reason they’re not proficient welders—this is more the domain of the fabricator than the repair mechanic. Don’t feel bad if this isn’t your strong suit. I’m not a trained machinist, though I practice making chips fly when I am able. Remember, if you can get the subassembly free from the vehicle, you’ll often be money-up to bring the workpiece to a professional. There’s no shame at all in knowing the limit of your capability.