I am actually a qualified automotive engineer by trade,but
...metallurgical sciences are a different kind of animal. Far be it from me to contest anecdotal experience but I resort to science for the win.
As usual there is a TLDR at the end whenever I produce a wall of text.
The short version of those eight pages is intake vale steels possibly and exhaust steels not so much .
Exhaust steels are better suited to corrosion and high temperature resistance.
Intake valve steels differ in their carbon, nickel and chromium content. (yes , I know "other alloying elements")
So we're not going to be burning through our work so exhaust valves can be largely ignored.
We're not going to make a cutting tool out of any stainless related material because it won't hold and edge or take heat treat to any extent.
That leaves the higher carbon content intake valves.
This leads to time at temperature (heat soak times) and a decision to temper back or leave them as is.
It would then follow that most of the rough machining of the valve should be done in an annealed state.
Next we have the irregular wear on the valve stem. For accuracy a new valve should be used.
Finally we have the question, why? Here follows my anecdotal tale. I haven't always had access to proper tooling because of remote locations, lead times, or simply money. Instead I made what I could from what I had,
The first instance was re-cutting the pocket for a valve seat in an aluminum head after welding.
The next case was an involute gear cutter with the teeth form cut to 24DP 14 1/2PA the material was 12L14.
Later a multi tooth abortion of a fly cutter for surfacing small bits of 6061. This lasted only until the fly cutter arrived.
The list goes on but I think you get the idea. The important point is to experiment without reinventing the carbon atom. Simply put , all it took was a set of hardness testing files to determine if my heat soak and temper process was effective or if I was wasting my time. You have to have some indicator of hardness other than "did it hold an edge in the cut". I lost an identifiable amount of time educating myself in metallurgical properties as a result.
TLDR version
Exhaust valve, no.
Stainless valve, no.
Used valve, not the best idea.
Intake valves with identifiable carbon content.
Understand heat treat processes.
Have some way to test the heat treat.
Don't let anyone tell you it can't be done.
YMMV