Identification of real pitch difference in bolt-nut connection to improve anti-loosening performance and fatigue strength

In a wide industrial field, the bolt-nut joint is unitized as an important machine element and widely used. To ensure the safety of the structure and reduce cost, low-cost bolt-nut connections with good anti-loosening performance and high fatigue strength are always required. In our previous papers, the effect of pitch difference between a bolt and nut was studied. Under a small pitch difference, anti-loosening performance is not enough. Under a large pitch difference, fatigue strength is not good. Therefore, in order to improve both anti-fatigue and anti-loose performance, the choice of suitable pitch difference is very important although the manufacturing errors always appear in bolt-nut connection. Until now, the result of experiment and analysis without manufacturing error but is not match. Since even small manufacturing errors may affect anti-fatigue and anti-loose performance, in this paper how identification of real pitch difference is discussed after the pitch difference nut is produced. Also, the accuracy of the identified pitch difference is confirmed. By using the confirmed error, the machining accuracy may be improved to ensure the nut has good performance.