We have had good results with plasma spray to build up worn surfaces but usually only do it on very expensive or rare parts. If common it's cheaper to buy new. Bought the set up after hearing hype on repairing "lacey" rusted areas in floor pans and other areas. It ended up not being better in time or cost than just replacing the panels but it does work good for worn shaft repair and doesn't heat shaft to extreme temps like welding. If you google "plasma spray welding" there is a you tube video showing the process. I'd fire the guy running the lathe because if you hear the cutting tool making that sound it's leaving chatter marks on the surface. Maybe he's roughing it in and follows up with a tool post grinder (I hope).
