Originally Posted by Beagle

That deep score mark was caused by the boring bar tool. The idiot machinist did not wind back the tool before lifting out the boring bar. The depth of the score mark is an indication of just how blunt the tool was and how far it was pushing the bar away. A properly sharpened tool would have scarcely left a mark at all even if he hadn't wound back! A score that deep is bad news as it allows hot gasses to escape that can eventually burn a vertical groove in the piston. SUE THEM!