I operated several lathes that size while working for a Ship Yard. It was the most boring job I ever had. They were setup to turn propeller shafts. We would turn the shafts to clean up the surfaces. Then they were put on an older lathe that was setup to weld a stainless steel surface on them. Then they were returned where we turned the shafts to it's final size, hopefully without hitting any pits or voids in the stainless. A single pass would take many hours. The only time we would be standing at the lathe was threading the end and cutting the tapered section where the propeller was mounted on the shaft. I wish I had taken a picture of the huge horizontal mill that cut the keyways in those shafts.