For Hex Flange Nuts, ISO 4161 defines dimensions, tolerances and product grades. The sections below describe its scope, what it does NOT cover, and the equivalents across DIN, ISO and ASME.
ISO 4161 — Scope
ISO 4161 specifies the dimensions and tolerances of hex flange nuts. Material, property class, surface finish and packaging are governed by separate documents in the same standards family (for example ISO 898-1 for the mechanical property classes of bolts and screws).
Tolerance & Product Grades
ISO 4161, alongside the related ISO 4161 / DIN 6923 entries on this site, specifies product grades (typically A or B for fine work and C for general engineering) and tolerance classes for the controlling dimensions. Choose the grade against the precision your application requires.
Dimensions Specified by ISO 4161
| Size | Pitch (mm) | Flange diameter dc (mm) | Nut height m (mm) | Width across flats s (mm) | Reference standard |
|---|---|---|---|---|---|
| M5 | 0.8 | 11.8 | 5.0 | 8.0 | ISO 4161 / DIN 6923 |
| M6 | 1.0 | 14.2 | 6.0 | 10.0 | ISO 4161 / DIN 6923 |
| M8 | 1.25 | 17.9 | 8.0 | 13.0 | ISO 4161 / DIN 6923 |
| M10 | 1.5 | 21.8 | 10.0 | 15.0 | ISO 4161 / DIN 6923 |
| M12 | 1.75 | 26.0 | 12.0 | 18.0 | ISO 4161 / DIN 6923 |
| M14 | 2.0 | 29.9 | 14.0 | 21.0 | ISO 4161 / DIN 6923 |
| M16 | 2.0 | 34.5 | 16.0 | 24.0 | ISO 4161 / DIN 6923 |
| M20 | 2.5 | 42.8 | 20.0 | 30.0 | ISO 4161 / DIN 6923 |
| M24 | 3.0 | 51.1 | 24.0 | 36.0 | ISO 4161 / DIN 6923 |
Equivalent Standards
Where direct equivalents exist (ISO ↔ DIN, ISO ↔ ASME), they are listed on the parent Hex Flange Nuts page. Always confirm against the dimensions on this page, since some "equivalent" standards differ in tolerances and head geometry.
When to Specify ISO 4161
Choose ISO 4161 for international engineering work and OEM supply where ISO standards are the contractual reference. It is the default modern specification for hex flange nuts.