ISO 4161 is the governing dimensional standard for hex flange nuts. This page sets out the scope of the standard, reproduces the full size table it specifies, and lists the DIN/ISO/ASME cross-references commonly cited in datasheets and drawings.
ISO 4161 — Scope
ISO 4161 is "Hexagon nuts with flange — Coarse thread".
Material, property class, surface finish and packaging are governed by separate documents — ISO 898-1 and ISO 898-2 for mechanical property classes, ISO 4042 for electroplated finishes.
Tolerance & Product Grades
ISO 4161 does not divide hex flange nuts into product grades. Tolerances are given as limits on the individual dimensions in the table.
Where a general-tolerance class is cited on the drawing instead, it applies to the dimensions not otherwise toleranced.
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.
Companion Standards
ISO 4161 controls only the geometry of hex flange nuts. The mechanical strength is set by ISO 898-1 (bolts, screws and studs) or ISO 898-2 (nuts); the surface finish is governed by separate finish standards such as ISO 4042 for electroplating. For corrosion testing, the relevant document is ISO 9227 (neutral salt spray).
Custom manufacturing · Made to drawing
Need a nut to this standard in a non-standard size?
Parts built to ISO 4161 are already in the catalog, so a special is usually a variation on existing tooling rather than a new design — which is what keeps the cost down. Made by cold heading or tapping.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
