The use of Torx allows to transmit a higher tightening torque than other impressions. It is a universal type of impression, unlike the specific ones that are used in the various countries of the world (cross, philips, pozi, slotted, square impressions and so on). Torx is particularly suitable for diameters from 4 upwards; applying it on smaller diameters is not particularly recommended as the reduced depth of the impression with respect to a cross can create problems during assembly. Precisely for this reason, if they are not perfectly mounted in axis with the holes and with the screwdriver, the insert could escape from the screw seat.
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, on the other hand, the indentation scrapes the metal surface, 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 in itself is much more performing.
VITI M 6X20 TBL TX TESTA 14+0 10.9 Z.NERE Cr.3 + FRENAFIL 360°