Inspecting a fastener delivery

Twelve checks, in the order a QC inspector does them at the gate. Most take a minute; together they catch nearly every substitution, mis-supply and counterfeit before it reaches the structure.

1. Paperwork against order. Delivery note, packing list and purchase order agree on standard, size, length, grade, finish and quantity. A "DIN 931" order delivered as "DIN 933" is a different product, not a typo.
2. Certificate present and of the right type. EN 10204 3.1 (or the ASTM mill test report) is issued by the manufacturer's inspection department independent of production, for this heat and lot, showing the tested yield, tensile, hardness and chemistry. A 2.1 or 2.2 is a declaration, not a test.
3. Heat / lot number matches. The number on the certificate appears on the carton label and, for structural and pressure fasteners, on the product itself. No match, no traceability.
4. Head marking. Metric bolts: property class and manufacturer's mark on the head. A325M: three radial lines. A490M: "A490M". Studs: "B7". F1554 anchor bolts: blue / yellow / red end colour. Unmarked "high tensile" bolts are not high tensile.
5. Nut marking. Class 8, 10 or 12 marked on the face or chamfer; A194 2H marked "2H". Check the nut class against the bolt class — this is where most quiet downgrades sit.
6. Across-flats with a vernier. Confirms the standard (DIN vs ISO differ at M10, M12, M14, M22) and catches undersize heads on cheap product.
7. Thread with a gauge. A go/no-go gauge in the tolerance class on the drawing (6g bolt, 6H nut). Galvanized nuts are oversize-tapped and gauge differently — expect and record it.
8. Length and thread length. Length under the head; thread length against the standard (2d+6 up to 125 mm on ISO 4014). Short thread on a partial-thread bolt means the nut may not reach.
9. Coating thickness. Magnetic gauge on five pieces: hot-dip galvanized to ISO 1461 (50 μm mean on threads ≥ 6 mm), zinc plating to ISO 4042 (5–12 μm typical). Bare patches, drips in the thread and flaking chamfers are rejects.
10. Hardness spot check. A portable hardness tester on a sample confirms the class is plausible: 8.8 sits at 250–320 HV, 10.9 at 320–380 HV. A "10.9" that reads 260 HV is not 10.9.
11. Visual: cracks, laps, burrs, rust. Quench cracks at the head-to-shank radius and thread laps are rejection criteria under ISO 6157. Surface rust on plain product is cosmetic; on plated product it means the coating failed.
12. Sample and retain. Keep five pieces per lot with the certificate for the project file. If a question arises after installation, that sample is the evidence.