DIN Fasteners Guide: Standards, Grades, Finishes and Sourcing
What DIN standards mean, the most common bolts, nuts and screws, strength grades 4.8–12.9, stainless A2/A4, finishes and corrosion, and a sourcing checklist for OEM buyers.
What a DIN standard actually tells you
A DIN number defines the geometry of a fastener: head shape, thread, dimensions and tolerances. DIN 933, for example, is a hex head bolt with full thread; DIN 934 is the matching hex nut; DIN 912 is a socket head cap screw; DIN 985 is a nylon insert lock nut; DIN 965 is a countersunk head machine screw. Knowing the DIN number lets you specify the exact product without ambiguity, regardless of supplier. Many DIN standards now have ISO equivalents (for example DIN 933 ≈ ISO 4017, DIN 912 ≈ ISO 4762), and suppliers normally deliver to both. When you send us a BOM with DIN numbers and sizes, we can quote accurately and cross-reference the ISO equivalent if needed.
Grades, materials and when to use them
Strength grades describe the mechanical properties of steel fasteners: 4.8 (low carbon, general use), 8.8 (structural, the most common high-strength grade), 10.9 and 12.9 (automotive and high-load applications). Stainless grades are different: A2 (304) is the standard corrosion-resistant choice for interiors and general industry; A4 (316) adds molybdenum and is specified for marine, coastal and chemical environments. For high-temperature service — turbines, exhausts, furnaces — special alloys such as A453 Grade 660 are used. Rule of thumb: if you are unsure, 8.8 zinc-plated steel covers most furniture and construction needs; choose stainless where corrosion or hygiene matters; choose 12.9 or alloy grades where loads are high or temperatures extreme.
Finishes and corrosion protection
Zinc plating is the default finish for indoor steel fasteners: affordable, bright, and suitable for most environments. Hot-dip galvanizing gives a thick zinc layer for outdoor and construction use. Nickel provides a smooth, corrosion-resistant finish. Black oxide is a thin conversion coating used where appearance and minimal dimensional change matter. Black phosphating is common for drywall screws. Plain (uncoated) fasteners are used in stainless form. Ask suppliers for the salt spray hours their finish achieves — 48 hours is a reasonable minimum for plated indoor hardware, and higher hours for outdoor. Our fasteners are lot-traceable and salt spray testing is available on request.
OEM sourcing checklist
Before ordering fasteners from a factory, confirm: (1) DIN/ISO numbers and sizes (send a BOM); (2) grade or material — 8.8, 12.9, A2, A4, alloy; (3) finish and required salt spray hours; (4) head marking, packaging and quantities per SKU; (5) certificates (material, salt spray, batch traceability); (6) lead time and Incoterms (FOB/CIF/DDP). A serious supplier will answer all six in writing. Our MOQ is 5,000 pieces per item for custom marking and packaging, with smaller stock quantities available for standard items.
Frequently Asked Questions
It identifies the specific standard — for example DIN 933 hex bolts, DIN 934 hex nuts, DIN 985 lock nuts, DIN 912 socket cap screws.
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