I don't know if I have posted this before but:
To any of you who have lost Bach or Benge or Holton stop rod nuts, the threads is 5-40 which is non-standard. A very good replacement for these nuts is available at your local hardware store. Buy one nylon 4-40 nut and carefully split it along its length with a box cutter or similar. It will now thread onto the stop rod and be so tight that it cannot possibly vibrate off. You only need one.