Way back in the late 60's I went on an induction course and visited BREL, at Derby? There was a model carriage bogie which was being used to investigate "hunting" and the best profile was not a true cone but a "worn wheel profile" so we were told.
Possibly BR Research not BREL, as they were doing a lot of work on this about that time which is now incorporated in most later vehicle designs.
I think the reason for turning new wheels to a "worn" profile is that as they wear in service the profile doesn't change much. So the suspension only has to cope with one wheel profile, rather than having to deliver a smooth ride with "new", "fully worn" and everything in between.
Hunting is when the centreing of the wheel over-corrects for lateral displacements so the wheel overshoots to the other side and this results in lateral oscillation. For a particular set of circumstances there is always a critical speed above which it will occur - I remember travelling across Spain in a couchette in the 90s when I couldn't get any sleep because the oscillation would start like clockwork soon after starting from every station stop.
One solution is to provide dampers (shock absorbers) that restrict the rotation of the bogie, although this may increase wear on curves as the bogie is less able to align itself with the rails. The difference was very noticeable on the WCML between the Mk3s fitted with dampers and the Mk2s that weren't. I've also experienced hunting on a Karlsruhe tram-train at speed on the railway section, where I suspect damping of bogie rotation isn't possible as it would restrict the turning of the bogies into tight corners on the street.
