Standards in plain language

Defines the property classes 4.6 to 12.9: minimum tensile, yield, proof load, hardness range, elongation, and the tests that prove them. The class is a promise about strength, not about dimensions — a 8.8 bolt can be any shape.

Nut property classes 4 to 12 and the rule that the nut must develop the bolt's strength. Pairs nut class with bolt class. The standard also behind the "nut strips before bolt breaks" failure discussed in the guides.

Dimensions of hexagon head bolts: 4014 and 931 with a plain shank and partial thread, 4017 and 933 threaded to the head. ISO superseded DIN; across-flats differ at M10, M12, M14 and M22. Product grade A (finer tolerances) up to M24 and length 10d, grade B above.

Dimensions of hexagon nuts. ISO 4032 nuts are slightly taller than DIN 934 (M16: 14.8 vs 13 mm) — a reason the bolt-length calculator asks which one you are using.

Grades A1–A5 (austenitic), C (martensitic), F (ferritic), and property classes 50, 70, 80 by tensile strength in tens of MPa. A2 ≈ 304, A4 ≈ 316. The class is achieved by cold work, so large sizes are usually only class 50 or 70.

Coating requirements for galvanized bolts and nuts, including oversize tapping of the nut (or undersize rolling of the bolt) so the assembly still fits, and the strength limits: above class 8.8 the process must be qualified against embrittlement.

Coating thickness by steel thickness: for centrifuged articles such as fasteners, ≥ 6 mm requires 40 μm local / 50 μm mean minimum; below 6 mm, 20 / 25 μm. Appearance, adhesion and repair rules.

Consolidated in 2015 from A325, A325M, A490, A490M, F1852 and F2280. Grades A325M (830 MPa) and A490M (1040 MPa), Types 1 (plain carbon/alloy) and 3 (weathering). Requires rotational-capacity testing for galvanized assemblies.

A193 covers stud material (B7 alloy, B8 stainless, B16 for higher temperatures); A194 the matching nuts (2H, 8, 4). The pressure-flange pair. Marked on the end of the stud and the face of the nut.

Grades 36, 55 and 105 (yield in ksi), straight, bent or headed, with supplementary requirements for weldability (S1) and for permanent grade marking. End colour codes blue, yellow, red. The standard our own anchor bolts are made to.

Type 2.1 and 2.2: declarations by the manufacturer without specific test results. Type 3.1: test results for the specific lot, certified by the manufacturer's authorised inspection representative independent of production. Type 3.2: as 3.1, also countersigned by a third party. For traceability, 3.1 is the minimum worth having.

Which cracks, laps, seams, folds and voids are acceptable on bolts and nuts, and which are rejects. The reference when a visual inspection raises a question.