Skirting board screws T15 with nylon dowel, burnished 3.5x40

TORX (from the English word ‘torque’) is the registered word mark for a screw drive profile, the standard designation for which is ‘internal six-lobe’ (English: ‘six lobe, internal socket’). With the six-lobe internal socket, the screw and tool are subjected to less radial stress than with the traditional internal hexagon, and consequently suffer less damage. Torque is transmitted more directly via the radial parts of the tooth flanks rather than via the faces of the hexagon.

Steel is an iron-carbon alloy with a maximum carbon content of 2% by mass. The steels achieve their intended physical and mechanical properties through various hardening, annealing and tempering processes. It is also possible to harden the edge zone by surface hardening, case hardening or nitriding. Well-known steel grades are structural steels, free-machining steels, case-hardening steels, nitriding steels, tempering steels, tool steels and stainless steels.

Blackening is carried out in accordance with DIN 50938. Due to the thinness of the conversion coating – approximately one micrometre – the workpieces retain their dimensional stability to a large extent. Blackened fasteners offer only very limited protection against corrosion. Consequently, this process involves the constant-climate condensation test in accordance with DIN EN ISO 6270-2-CH, as well as the acetic acid and oxalic acid tests.