I have a piece of 6061-T6 aluminum (4" by 12" by 1/2") that I want to cut to a uniform arbitrary thickness but a close tolerance to flat (+ or - .001"). The surface finish should look "professional". I have a small horizontal mill, a small vertical mill, a surface grinder and a belt sander available. All are big enough to handle the piece without a second setup.
Which machine would you use and why?
Gary