This is not high-speed 'Z' level type machining demo, check out how they are using the side of tools for the machining of the cavity from the bottom up. This was a method my old company develope 12+ years ago for Bridgeport UK VMC to enable them to use their 10,000 rpm spindle to complete with high-speed machining center for hard metal machining: http://www.cnczone.com/forums/video....ils&videoid=33