Hexagon nuts ~0,5d DIN 439B-04 burnished M5

The wrench sizes for hexagon bolts and nuts are specified in ISO 272: 1982-01. The nominal wrench size on the workpiece (e.g. bolt, nut) is the same as that on the tool. However, there is some play between the two to allow the tool to be fitted without difficulty. The relationship between the nominal diameter d of the thread and the wrench size s is standardised in EN ISO 4014 and EN ISO 4017 for hexagon bolts, and in EN ISO 4032 for hexagon nuts (dimensions in mm).

In contrast to screws, the strength class for nuts in steel only describes one key figure. This is the test stress S. It can be equated with the tensile strength Rm of the screw. Nuts with a two-digit number (e.g. 04) describe low nuts. This hexagon nut is used for screw connections with limited load capacity, e.g. as a lock nut

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.