Right, that's the idea I was trying to express. Don't expect anything good to happen if you try to plunge a ball end mill straight down into the material. The

Right, that's the idea I was trying to express. Don't expect anything good to happen if you try to plunge a ball end mill straight down into the material. The thought was only that a large-radius ball would be able to approximate the sphere to within tolerance with larger stepover than a smaller tool. After bulk material removal with a more suitable cylindrical tool of course. With a little bit of googling I discovered a different class of end mill called a circle segment tool, which could potentially make short work of the problem in a 5-axis machine: https://www.moldmakingtechnology.com/videos/circle-segment-tools-and-toolpaths-in-action https://www.moldmakingtechnology.com/videos/circle-segment-t... Would love to see how Apple does it, but it's never happening. I'm not really a machinist either, but let's not allow that to stop us from incorrecting each other on HN!