What are the rejection/acceptance standards for shaft threads? How are threads accepted/rejected?

My problem is as follows. We overhaul Gas Turbines. The shaft threads of a rotor, where it mates with the bearing lock nut are worn out. Can somebody tell me where one can find standards for acceptance/rejection of shaft threads. Lock nut is no issue as new ones are readily available. The worn out threads are not badly damaged, but considering the 'quality control' requirements this question has been posed. Can I get some references so that a decision to accept/reject the rotor can be made. Would appreciate an early reply.