What is the requirement standard for bolt re-tightening in the sky railway?

50—70%。 According to the official inquiry of the railway chaotian, the required standard for re-tightening the railway chaotian bolts is 50-70%. Bolt is a mechanical part, a cylindrical threaded fastener with nut, which is a kind of fastener composed of head and screw. It needs to cooperate with nut to firmly connect two parts with through holes. This connection form is called bolt connection. If the nut is unscrewed from the bolt, the two parts can be separated, so the bolt connection is detachable.