Funny you should mention that. There are tool marks on stones all over the Giza complex, that could not have been made by anything other than advanced machinery.
Check out some of Brien Foerster's videos on YouTube. He's spent years studying ancient megalithic sites around the world.
Man that would be quite a puzzle to try to unravel.
With enough laborers and patience, I could envision a kind of grind-down process, using crude diamonds or another hard substance like carborundum, embedded in a metal plate that itself had first been finely ground flat.