Traditional Culture Encyclopedia - Photography and portraiture - The screws on the switch slide rail are white outside.

The screws on the switch slide rail are white outside.

The aperture of the screw column is small. The external whitening of the switch sliding screw is due to the small hole diameter of the screw column and the deformation behind the screw. When the deformation is greater than the elongation, stress shrinkage deformation and whitening will occur. Screw is a tool to tighten instruments and parts step by step by using the physical and mathematical principles of circular rotation and friction of the inclined plane of an object.