I would like to create an array of 6 mm dia round posts, 6 mm tall, on a 1 x 1" square array, Aluminum 6061 or better yet, 7075. The diameter of posts needs to be to within 0.001" tolerance, as they would slide-fit onto a reciprocal array of 6 mm holes. Is there a specialty endmill with blades facing inwards, to create the posts in one cut, and 'fill in' the unmilled surfce with a regular mill? Googling did not produce a result. Or is CNC the only method to achieve this?