Prevailing torque nut with metal insert is designed in accordance with engineering basic principal. A spring ring is inserted onto a nut, so two pieces are to be formed an integral unit as a safety nut. When the unt is tighten on the bolt or screw, tensional force on the spring ring ensures the nut to be locked securely. Within the designed torque limit, this typical nut provides good mechanical feature and wear characteristics so that nut can be used repeatedly for a reasonable period. Under severe vibrated or thermal (-30℃ to 300℃ ) operation environment , the nut still maintains its good mechanical performance.