Microstructure, streamline and Microhardness of different size BTI6 locknuts have been analyzed and compared with 08 mm thread made of BT16. The results show that the microstructure of BT16 fastener is lamellar type with very fine grain size, which may be obtained by deformed starting in beta field. Microstructure of fastener is very similar with that of thread in annealing state, which show that the fastener is used in annealing state without solution and aging treatment. Streamline and hardness analyses show that fastener is deformed in cold condition.