Rolling theoretical rotation axis line of the inner ring to the center axis line of bearings, thrust bearings on the shaft circle refers to the axis line.

If a gyro is used to measure the rate of rotation around the aircraft roll axis, it will measure a non-zero value as long as the aircraft is rolling, but measure zero if the roll stops.

The problems in lock nut of roll axis and sleeve of precision rolling mill are analyzed, some measures proposed, good result got.