Looking to mill some pockets in 4140PH and have some corner radius of 0.200 to depth of 0.500 which means a small diameter cutter. Plate is actually 0.500 and holes clear through so not actually pockets I suppose. If needed I could fixture and mill some from both sides but I need smooth walls. Saw some on using boring cuts rather than side milling - seems like a good plan using either an end mill or a drill (undersize) doing the corners first to avoid flex. Might be able to increase the radius min to 0.250. Planning to use carbide 4 flute end mills. I know one option is to go to higher flute count but hoping to avoid that unless really needed. Is 2x diameter reasonable in this material and what sort of chip load and techniques?