Live in a machine shop - thats sick Deano -although most machine shops need someone to clean and polish the machines
Its imperative that the "hot spots" or surface hardening is completely removed -- the lathe is most efficient at this.
The planetary surface grinder is
not the best for (performance) flywheels,
The process would take ages to grind out 1mm and using a magnetic chuck which stresses the surface out of shape also.