The re-inspection of the quality certification documents is mainly to check the certificate of the fasteners, especially the batch number or the date of manufacture of the fasteners to ensure the traceability of the fasteners. In addition, the packaging, marking and quantity of the fasteners should be checked to ensure consistency between the received product and the contract. The appearance and size re-inspection is mainly to check the surface quality of the fastener, the coating layer and the important dimensions, such as the thread precision of the threaded fastener, the diameter of the shear fastener, and the like. Basic performance re-inspection is a mandatory requirement for aerospace systems at specific times. The re-inspection project specified in the mandatory standard QJ3112-1998 is the basic project to ensure the basic function of the fasteners. The project is as small as possible and the method is as simple as possible. But this does not mean that the unchecked items can be unqualified. Users can re-examine the items of interest according to their own experience or purpose of use. Any failure of the item can be a reason for rejection. Re-inspection is the responsibility of the fastener user. The user can re-inspect it himself or commission a re-inspection. Whether it is identification test, quality consistency test, or re-inspection into the factory, it is generally a sampling test, there are risks, and can not guarantee the product's percentage. The basic concept of random sampling of three fasteners The random sampling scheme is a sampling rule designed according to the principle of mathematical statistics. For any given sampling plan, when the quality of the whole batch of fasteners is good, the rate of non-conforming product is small, the probability of receiving L(p) is large, and when the quality of the whole batch of products is poor, the rate of non-conforming products is low. p is relatively large, and the reception probability L(p) is small. Therefore, for the same sampling plan (n, Ac), the probability of reception varies with the rate of defective p of the batch. Mini Screwdriver,Key Chain Screwdriver,Iphone Screw Driver,Mini Pocket Screwdriver Yucheng Weisite Measuring Tools Co., Ltd , https://www.wsttools.com