# Fastener # Why does the combination screw slip?

1. The combined screw is used on the iron plate, which is very hard and will slip after repeated use. 2. The hardness of the combined screw itself is not hard enough or even weak. 3. The material of combination screw is not good, that is to say, the spiral used to produce combination screw is not so good. Not hard enough. 4. The combined screw is not hardened, which can not meet the customer's requirements for the hardness of the combined screw. Therefore, generally speaking, if the hardness requirement is high, 8.8 grade combination screws should be used. The hardness of grade 4.8 combined screws can't reach the index. View original post >>