An employee was operating a large dial machine that presses valve seats into an aluminum head when the hydraulic ram did not properly feed a valve seat. He opened the door, activating the interlock, and went to the control panel to place the station in manual mode so he could jog the feeder arm and displace the valve seat to reload another seat. The down side of the selector switch was activated, pinching and amputating his fingertip between the small ram and the valve seat.