Hex socket set screws with conical head ISO 4026-45H coated zinc flake M20x80 mm

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.

Zinc flake coatings are non-electrolytically applied coatings in accordance with DIN EN ISO 10683. Additional top coats and lubricants may be applied. As this is a non-electrolytic process, no hydrogen is produced which could cause the components to become brittle. This requires correct pre-treatment. The corrosion protection is 10 times greater than that provided by electroplated coatings of the same thickness.

Compared with a Phillips-head screw of the same size, a hex socket screw can withstand around ten times the torque. Hex socket screws are well suited to bolted joints where the screw heads are difficult to access due to the design of the structure. Hex socket screws can be countersunk to save space if protruding screw heads are a problem.

Hardness classes are specified for set screws and similar fasteners that are not subject to tensile stress, which are regulated for stainless austenitic steels in ISO 3506-3 and for carbon steel and alloy steel in ISO 898-5. ISO 3506-3 defines the two hardness classes 12H and 21H, ISO 898-5 defines the four hardness classes 14H, 22H, 33H and 45H. The hardness class designation 45H means 450 HV (Vickers hardness).