On 2/24/2010 16:07, Mark Rand wrote:

My point was more along the lines that a boring head will to a better job of
an 18mm clearance hole than either of the end mills.

To be clear, I was milling pockets that the magnets will fit into that
will pull the scale display unit. These pockets are not thru, just very
close. IIRC, aluminum will not block the magnetic attraction all that
much. I hope...