Since I'm making gears for Metric threading, I did some work on the lead screw reverse. The Monarch toolroom lathes had had the LSR on the apron and it was a good deal. Their engine lathes had a lever on the headstock. There is a spring loaded ball inside the casting so you push the end in and then move the lever up or down until it hits a detent on the headstock. Works but not very handy. I didn't want to muck up the original so drilled and tapped a 5/16 hole and added an extension. While you can reverse the screw at lower rpm, I intend to use the clutch to stop the spindle when threading, hit the lever and reverse the feed and leave the half nut engaged. The clutch stops very quickly so it will work.