How to check screws

There are two types of screw surface inspections, one is the inspection before the screw is produced and not plated, and the other is the inspection after the screw is plated, that is to say, after the screw is hardened and the surface of the screw is treated. After the screws are produced and before electroplating, we inspect the screws in various aspects such as size and tolerance. See if there are national standards or customer requirements. After the surface treatment of the screws, we will inspect the plated screws, mainly to check the color of the plating and whether there are any broken screws. In this way, when we deliver screw goods to customers, customers can successfully pass the customs when they receive the goods. The following is a detailed description of Zhu Zhu, the manager of Chuanggu Screw, the inspection after the screw processing:
A. Appearance quality requirements
The inspection of the appearance of the screw is to inspect the appearance, electroplating layer and other aspects.
B, Inspection of screw coating thickness
1. Measuring method
The amount used has a micrometer, a vernier caliper, a plug gauge, etc.
2. Magnetic method
The magnetic method to measure the thickness of the coating layer is a non-destructive measurement of the non-magnetic coating layer on the magnetic substrate with a magnetic thickness gauge.
3. Microscopy
Microscopy is called metallographic method, which is to magnify the etched fasteners on a metallographic microscope with a micrometer eyepiece to measure the thickness of the coating on the section.
4. Chronoflow method
The timing liquid flow method is to use a solution that can dissolve the coating to flow on the local surface of the coating, and calculate the thickness of the coating according to the time required for the local coating to dissolve. There are also coating drop method, anodic dissolution Coulomb method, etc.
C. Inspection of the adhesion strength of screw coating
1. Friction polishing test; 2. File method test; 3. Scratch method; 4. Bending test; 5. Thermal shock test; 6. Extrusion method

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