To be honest – using 12mm or 1/2″ tool steel is a waste of money. 1/4″ or 3/8″ tool steel is about the largest i would go because – its cheaper, there is less to grind away and there is no way in hell you will overstretch the rigidity of the tool under even extreme machining on a ML10. If you are using tipped or indexable tools then, to allow for height adjustment through packing, go no larger than 12mm. Can you actually get 14mm tool steel or tip tool holders?