Question

Technician a says that when measuring a rotor's thickness variation, you should measure the rotor in a minimum of five to eight places around the face of the rotor. technician b says that as long as the rotor faces look smooth after machining them, you don't have to measure them again. who is correct?

Answer 1

Technician A is right. If you follow what he is saying you should eliminate the rotor's thickness variation, or at least it should be cut down to a minimum value.
If you have thickness variations that are this can lead to the force that acts on the axle around which the rotor is spinning. Even if the variation is very small at very high angular frequency this forces can become really huge and destroy the axle.