At present, commonly used self-tapping screws are cross-head and the first cross-type head of the two types, are more areas of the national standard, the surface treatment is usually zinc plating, production through quenching, which we usually heat treatment, the hardness Strengthen, but there are a small number of businesses have special requirements without heat treatment. The cost of heat treatment is naturally higher than without heat treatment, but the use of hardness without heat treatment, so it depends on the user what products.