High Performance Ball Endmills - Inch Sizes - +/-.0002 ...
He's not saying that the machines magically become more capable of grinding an endmill to size & form in Dc 12.0000mm than they are capable of grinding to sise & form in Dc 12.7000mm. He's saying that those companies don't even bother to offer them in the Dc 12.7000 sizes. Back on topic.