I think this has run its course 🤫 .The great reveal🎤.
It is for refacing the valve seating face on engine valves .Underside of valve facing the cutter being moved forward by the fine thread, whilst the valve is rotated by a handle clamped on the valve stem.
I am sure it would not work on the modern very hard valves.
Would you like another one ?? as Pompey-x says. I will get my coat😉
