Treadmill cylinder head mill - video

Treadmill cylinder head mill. 10:47 video:

https://www.youtube.com/watch?v=w2yuxe5E8jU

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.

Looks like he used a large plate of about 1/4" glass on top of the plywood.

Looks like a piece of marble @5.15 or some type of stone as a flat base below the glass.

Yes, looking closer I see the marble. Good catch.

Well, I am a skeptic!! First point is, if there is only 0.001" warp in the center of that long head, that is easily pulled out when installing the head and using proper torque sequence. The center of that head could be as much as 0.006" and be assembled with no leaks, IF it is properly torqued.

I did not watch the whole video, but if he did not check and true the block deck, it is pointless to surface the head. If he did not use coolant when "milling" it, the bottom of that head will get hotter than the top, causing it to expand, pushing the ends upward. If it is "milled" flat when hot, when it cools the the ends will drop back down.

What does he do to check the volume of each combustion chamber, then make them equal? It would be very easy to take more off of one end that the other which would change the combustion chamber volume for each cylinder?

He may have milled 1,000 heads on his machine, he will not be doing mine on that. It is easy to sell a service to someone who has no real idea what the guy is talking about.

He said (at 8:15) granite for a solid base with a piece of glass on top