025D

Self-tapping screws are mainly used for screwing on metal sheets and laminates through simple drilling, without threading or tapping operations. These screws are not particularly suitable for use on die-cast materials and plastic materials. For a safe and stable screwing, particular attention must be paid to the diameter of the hole to be drilled. A small hole in which the screw "forces" to enter is certainly not synonymous with greater guarantee in fixing. It should also be remembered that the existing tables are empirical and only give an indication of perforation, but they are not a certain rule, as the fixing must be checked from time to time according to the technical-mechanical conditions of the particular that will be tighten.

The underhead knurling has two distinct functions. Once the screw has been tightened, the indentation causes the unscrewing torque used to be greater, making the fixing more stable in all those applications which are subjected to movements and / or vibrations during their use. In the electric field, however, the indentation scrapes the surface of the metal, effectively creating connectivity with the material where grounding is required. However, it must be taken into account that the serration can never replace the tightening of a screw with the serrated washer, which is much more performing in itself.

Compared to the cross recess, the hexagonal head guarantees the possibility of applying a higher tightening torque without the risk of the insert coming out. It is particularly suitable for diameters from 4.8 upwards.

The length of the screw is measured from the tip to the underhead.