Guys,
As you have noted, that old movie from Colonial Williamsburg does show an early 20th century cast iron valve wheel on the boring machine. However, the current boring machine uses a much larger wagon wheel complete with wood spokes and an iron rim. It appears to me that the current one may result in too high a level of momentum which may result in damage or breakage of the boring bit when the cutter gets jammed. The current tool looks really nice, a work of art by itself. They were correct in replacing the cast iron valve wheel machine with a more period correct machine.
Jim