This is why you can't trust anyone to work on your car.

well, as a mechanic, I actually see People that should not have wrenched on they own cars as well! Im not defending shortcuts here..
Its not just the mechanics that destroy Things... :-) another thing is that at home you may have time to wait for that spare to show up, at work, everything takes time, and Labour is something the customer doesnt want to pay...

that said, we had a Young gun at Our shop that used the impact wrenc on a aluminum oil sump bold....I must say he was shocked when the Complete sump cracked in several pieces..LOL not so happy customer