DIN to ISO to ASME: a fastener cross-reference, and what actually changed

DIN 931, 933, 934 and 912 are withdrawn and replaced by ISO 4014, 4017, 4032 and 4762. The thread is the same, but across flats changed for M10, M12, M14 and M22, and ISO 4032 nuts are taller than DIN 934 nuts. ASME inch standards are a separate system, not an equivalent.

By Prashant Dwivedi, Managing Partner, Transworld Commercial Enterprises · Published 11 Nov 2026 · Updated 11 Nov 2026

Drawings in Europe still call up DIN fastener standards that have been withdrawn for years. The ISO replacements are close, but not identical. Knowing which dimensions changed tells you when a substitute is harmless and when it is not.

The main pairs

  • Hexagon head bolt, part thread: DIN 931 is replaced by ISO 4014 (EN ISO 4014).
  • Hexagon head screw, full thread: DIN 933 is replaced by ISO 4017. The current edition is ISO 4017:2022.
  • Hexagon nut: DIN 934 is replaced by ISO 4032 for coarse thread and ISO 8673 for fine thread. The current coarse-thread edition is ISO 4032:2023.
  • Socket head cap screw: DIN 912 is replaced by ISO 4762.

DIN Media lists each of these DIN standards as withdrawn, with the EN ISO edition as its replacement.

What changed: across flats

The width across flats, the spanner size, changed in four sizes:

  • M10: 17 mm in DIN, 16 mm in ISO
  • M12: 19 mm in DIN, 18 mm in ISO
  • M14: 22 mm in DIN, 21 mm in ISO
  • M22: 32 mm in DIN, 34 mm in ISO

The other sizes in our hexagon table share the same across flats. Fastener distributors describe the move from DIN 931 and 933 to ISO 4014 and 4017 as a change to ISO spanner sizes in these four sizes, otherwise interchangeable.

What changed: nut height

ISO 4032 nuts are taller than DIN 934 nuts in most sizes. From our size table, nominal height m in mm:

  • M10: 8 (DIN 934), 8.4 (ISO 4032)
  • M12: 10 and 10.8
  • M16: 13 and 14.8
  • M20: 16 and 18
  • M24: 19 and 21.5
  • M30: 24 and 25.6

The thread does not change, so the nuts assemble with the same bolts. What matters with nuts is the property class. Under ISO 898-2, a class 8 nut is for bolts up to 8.8 and a class 10 nut for bolts up to 10.9. A higher-class nut may replace a lower one, except for prevailing-torque nuts, where the classes must correspond.

Where ASME fits

ASME B18.2.1 covers inch-series hex bolts and screws. Inch and metric fasteners are different products, not equivalents: a cross-reference to ASME tells you which standard plays the same role, not which part will fit. On the metric side, ASME lists B18.2.3.5M, metric hex bolts, as withdrawn and kept for historical reference only. If a drawing names an ASME metric standard, check its status before ordering.

Write the order line

Name the standard your drawing uses, then the size, length, class and finish, for example Hexagon head screw ISO 4017 – M12 × 50 – 8.8 – zinc plated. If your drawing says DIN 933 and the spanner size matters, say so: in M12 the DIN head is 19 mm and the ISO head is 18 mm.

What to send

  1. The standard exactly as it appears on the drawing, and whether the ISO replacement is acceptable.
  2. Size, length, property class and finish for each line.
  3. The nut class and style, if nuts are part of the order.
  4. Quantities and the inspection document you need with the shipment.

Sources

  1. DIN 933:1987-09 Hexagon head screws threaded up to the head (withdrawn), DIN Media (accessed 11 Nov 2026)
  2. DIN 931-1 Hexagon head bolts with shank (withdrawn), DIN Media (accessed 11 Nov 2026)
  3. DIN 934:1987-10 Hexagon nuts with metric coarse and fine pitch thread (withdrawn), DIN Media (accessed 11 Nov 2026)
  4. DIN 912:1983-12 Hexagon socket head cap screws (withdrawn), DIN Media (accessed 11 Nov 2026)
  5. DIN EN ISO 4017:2022-10 Hexagon head screws, DIN Media (accessed 11 Nov 2026)
  6. ISO 4032:2023 Fasteners — Hexagon regular nuts (style 1), ISO (accessed 11 Nov 2026)
  7. ISO 898-2:2022 Nuts with specified property classes (sample pages), iTeh Standards (accessed 11 Nov 2026)
  8. DIN 933 > DIN EN ISO 4017 standardisation overview, Dresselhaus (accessed 11 Nov 2026)
  9. DIN 931-1 > DIN EN ISO 4014 standardisation overview, Dresselhaus (accessed 11 Nov 2026)
  10. ASME B18.2.1 Square, hex, heavy hex and askew head bolts and hex screws (inch series), ASME (accessed 11 Nov 2026)
  11. ASME B18.2.3.5M Metric hex bolts (withdrawn), ASME (accessed 11 Nov 2026)

Questions buyers ask.

Is DIN 933 the same as ISO 4017?

Almost. Both are hexagon head screws threaded up to the head, and DIN Media lists DIN 933 as withdrawn and replaced by EN ISO 4017. The across-flats dimension changed for M10, M12, M14 and M22, so those sizes need a different spanner. Other sizes match.

Can I use an ISO 4032 nut on a DIN 931 bolt?

Yes, the thread is the same. In M10, M12, M14 and M22 the nut and the bolt head take different spanner sizes, and the ISO nut is taller. Match the nut class to the bolt under ISO 898-2: class 8 nuts for 8.8 bolts, class 10 for 10.9.

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Specification, quantity and destination. PDF, DWG, DXF and STEP welcome.

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