Keywords: Fasteners; Steels; Mechanical properties of materials; Unalloyed steels; Alloy steels; Threaded fasteners; Threaded components; Screws (bolts); Set screws; Hexagonal-head fasteners; Temperature; Designations; Classification systems ; Conformity; Hardness; Hardness testing; Rockwell hardness measurement; Brinell hardness measurement ; Vickers hardness measurement; Strength of materials ; Length; Height; Torque; Surface properties ; Sampling methods; Testing conditions; Test specimens; Decarburization