When this setup is running, a 3-inch Mitsubishi high-feed cutter is opening up an inner cavity in a big A106 block on a Mazak 8800 horizontal mill. The spindle spins fast, small chips and dust spray out of the hole, and the cut keeps eating metal at 700 SFM with a .250 feed. That is a lot of cutter at work in one spot.
The holding method stands out to me. The block is clamped from the top with plates fastened down by long threaded bolts. For cuts this aggressive, that looks like a sensible way to keep a large part from going anywhere, at least in my view.
The detail I keep coming back to is the spindle carrying an extended tool that reaches down into the internal pocket. Running a cutter that size on an extension is where I would expect any chatter or deflection to show up first, and nothing in the run suggests trouble there.
One open item is insert management. Edges get turned to a fresh position about every three hours, which is a hands-on maintenance rhythm to keep up with. There are also no material removal rate figures shared yet, which is the number many people would want before comparing notes. Coolant droplets on the enclosure walls and the machine base give a sense of how wet this cut runs.