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DT,
I suspect your right-wrongometer is reading correctly. But it may be influenced by the financial and contractual shenanigans that FMEA has reported, but which are only of interest to Honda and Co. X.
As I understand it, the bolt is just as strong in terms of "snapping off" as it should be. This is because this strength is proportional to its minor diameter, which is correct.
What is missing, is the very top of the mountain of the thread. The forces in a thread are mostly taken by the middle and the bottom of the mountain, so how much the thread is weakened can only be established by careful calculation.
If the thread is seriously weakened, then when you tightened the nut then the thread would fail. This hasn't happened here.
But (and this is FMEA's point) in use on a car, the changing loads can fatigue a part of the thread, causing the thread to stretch a bit. The nut won't come loose, because it is keyed on, but the preload on the bearing could reduce.
If this happens, the bearing will gradually fail. The failure would include a gradual increase in friction, and the most terrible grinding noise from the rear of the car. If you continued like this for many hundreds of miles (shouting over the noise) then ultimately the failed bearing could lead to the spindle failing.
If ever there was a rear bearing failure, then I'm sure Honda would examine the bearing and spindle carefully to see if it was caused by a fatigued thread. But the practical tests on the thread showed that it was so massively over engineered, that fatigue is extremely unlikely.
QA people have the "power" to reject goods. This "power" is often written in to manuals in such a way that not even the MD has the ability to over-rule. In my experience, QA people get very upset indeed when their power is over-ruled, and I see this in FMEA's tone. Normally though, the bad feeling subsides after a rational explanation is shown and life then goes on as normal.
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