pics to show what youre talking about?
I'm assuming most here understand the basic principles of turbo shaft and wheel alignment. Just like a car wheel has to be balanced correctly, otherwise there will be an off axis wobble when it spins up. With a turbo, to balance the wheel, it is spun very quickly and a computer determines where it is off centered at when it spins. Then either an employee or machine takes material off of the wheel or shaft nut to balance that out.
IHI turbos are put together in mass. When they are aligned, a computer reads the off centered rotation and a robotic arm grinds the material until the comp says it is spinning within tolerance/spec.
If a turbo nut has multiple grind marks (they have to have atleast one) it indicates the shaft was more on the extreme side of balancing before it was shaved. All the blown turbos I've seen, have multiple oem angle grind marks from the factory. This is the only pattern I've been able to find. As I've been trying to find a failure cause for over one year. The car has seen 3 different turbos now. All have 1 , shallow angle grind and all have been rock solid. 5 have blown in SI, all had two very deep grinds to force a balance. In theory it should not influence it, but all blown turbos I've seen have two grinds or one very deep one....