The first non-standard screw is also the evolution of the national standard screw. It is also necessary to determine the specific inspection items according to the surface defect specification of the national standard screw. For details, please refer to the corresponding national standards. Assuming that the surface coating and coating affect the identification of surface defects, it should be Pick up before examination.

Secondly, check the dimensions and materials of non-standard screws according to the requirements of the design drawings.

This should pay attention to the inspection of the material:

1. The raw material manufacturer should provide a statement of the raw material certificate.

2. High-end products must require SGS material certification, and send to the relevant laboratory for material composition analysis to confirm whether the composition content meets the requirements of the drawing material.

Once again, the function requires non-destructive inspection. During non-destructive inspection of non-standard screws, if there are quenching cracks on any part, wrinkles on the support surface and below, and whether the coating meets the environmental protection requirements of RoSH, etc.

Then there is the destructive inspection. For example, the hardness level of non-standard screws is subjected to corresponding hardness impact inspection; internal hardness, mechanical properties, torsion inspection, etc. will damage non-standard screws, but screw factories with a strong concept of quality are all these. It is necessary to do inspection items.