1. In terms of product type, the external hexagon screw bears a relatively larger torque, while the inner hexagon screw bears a smaller torque, and the cross groove bears a smaller torque. In the use of supporting products, we generally recommend the choice of screw grade than screw grade a higher, so the most economic benefits.
2, the product material grade, mainly about our common carbon steel exhibition screw, according to the level of carbon content, we are divided into: C1008(corresponding to 4.8 level), C1035(corresponding to 8.8 level), C1045(corresponding to 10.9 level), SCM435(corresponding to 12.9 level and 45H), the higher the carbon content, the harder the material. All screws from 8.8 to above are of high strength.
3. For specifications, such as M4x8, the outer diameter of 4 finger teeth is 4mm, and the effective length of 8 finger teeth is 8mm for embedding the loaded object. Generally, the total length of countersunk head screw is loaded, and the length of half head should be added to the semi-countersunk head screw. The pan head screw cross does not contain head size.
4, the same material when doing heat treatment, the higher the hardness, the worse the toughness. Heat treatment is required for electroplating of grade 8.8 or above. There are two kinds of heat treatment: high strength screws need tempering and tempering heat treatment, that is, the hardness of screws is uniform from inside to outside; Self-tapping nails need carburizing heat treatment, that is, a layer of carbon on the surface of the screw, very hard, but the inside is very soft, if carburizing to the inside of the screw will be burned.