Hex socket cap screw according to ANSI B18.3 standard with UNF (Unified National Fine) thread, strength class 12.9, plain (uncoated) surface. The design corresponds to ISO 4762 but uses a fine inch thread, providing improved tightening control, greater thread engagement, and better vibration resistance. The plain finish is used in dry or controlled environments or when the screw will later be coated, for example with painting, flake coating, or hot-dip galvanizing (HDG). Class 12.9 screws offer very high tensile and clamping strength for machinery, precision assemblies, and imported equipment where UNF threads are standard. Available in multiple lengths and dimensions from SWEBOLT & BOTNIA BOLT.