Treadmill cylinder head mill - video

[metric_taper]

Did I miss where he talks about the platen surface material? I saw plywood, but I would think some sort of graphite infused material, I've seen on some existing treadmills would be the wanted material. I also don't recall what grit he used on the head sander, seems it has to be fine to enable crush cylinder head gaskets to seal.
I think you would just call this a power lapping machine.