RE: ringed engine break in?
proptop:
Back in the stone age we used what was referred to as an "Air Mike" for the really precise measurements, and centerless grinders for the finish sizing. The air mike could read to a millionth inch, and since it read the flow restriction on a column of air it automatically blew all the dust away, and the oil film as well. Now that we have laser interferometers we can measure to a billionth of an inch.
CNC machining is convenient, and gives part after part with almost no variation in any dimension. But anything you can do with CNC can be done by a skilled operator, provided he has machine tools of similar quality. But the unit production cost will be much higher - a lot more labor time by a high priced worker. Doesn't take a lot of skill to clamp a work piece in the chuck and push the button, then go to the next machine and do it again. This is the biggest selling point of CNC.
This is not to say you aren’t a good machinist, but you do have to admit the skill requirement for loading a transfer machine is minimal.
Bill.