Machining with an engine lathe I wouldn't consider cobble work. However, you are correct when it comes to labor cost. We usually only do them when it's something special that the typical automotive machine shop can't or won't do. Also, sometimes the guys in the shop would rather do their own instead of buying new after-market ones, as not very many places turn them anymore. Not to mention, here we can skim off the minimal amount of material needed compared to the typical automotive machine shop that will most likely try and take as much as possible to obtain full clean up as quickly as they can.
There are no rules that say you have to machine both sides of a rotor (straddle facing) at the same time to guarantee zero runout or true parallelism (at least within .0005). The trick is to not remove the rotor from the chuck or mandrel until both sides are machined. Both left- and right-hand tool holders are utilized, just one at a time.
Carbide? Yes, we spend thousands of dollars on carbide tooling (inserts, tool bits, end mills etc.) every year. Pretty much all we use these days.
Back in the 80's and early 90's we used to manufacture tens of thousands of mainframe computer hubs for Control Data, Seagate and many others. Radial runout had to be held at .00015 max and parallel within .0001. We used diamond tipped inserts for them.
Getting back to the lathe. I think it's more of a cool conversation piece than a useful item to have taking up floor space.
Once again, this is just my opinion and no disrespect intended. I still wouldn't be concerned to try and turn a drum or rotor on that lathe.
John
