Somewhat cleaned up, some of the flaking starting to show through the “patina.” The spur gear engages a rack on the slider which will advance or retract the grinding wheel relative to the work being machined. This is the last stage of a DEEP gear reduction. Every 4 clicks on the feed wheel ratchet at the operator’s station rotates the spur gear enough to advance or retract the wheel slide a distance of .0005” or .012mm This is no ordinary spur gear. Can’t just order one of these...