Hex Weld Nuts with Flange manufactured to ISO 21670 are dimensioned by the size table reproduced on this page. The standard fixes geometry and tolerances only; material and property class are assigned by separate documents, and surface finish by separate finish standards.
ISO 21670 — Scope
ISO 21670 is "Hexagon weld nuts with flange".
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 21670 does not divide hex weld nuts with flange 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 21670
| Size | Pitch P (mm) | b (mm) | c (mm) | d_a (mm) | d_c (mm) | Width across corners e (mm) | f (mm) | g (mm) | m_min (mm) | Nut height m (mm) | Width across flats s (mm) | r_1 (mm) | r_2 (mm) | m1000 (mm) | Reference standard |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| M5 | 0.8 | 2.2 | 0.8 | 6 | 15.5 | 8.2 | 1.7 | 4 | 4.7 | 5 | 8 | 0.6 | 0.3 | 2.9 | ISO 21670 |
| M6 | 1 | 2.7 | 0.8 | 7 | 18.5 | 10.6 | 2 | 5 | 6.64 | 7 | 10 | 0.6 | 0.5 | 5.7 | ISO 21670 |
| M8 | 1.25 | 2.7 | 1 | 9.5 | 22.5 | 13.6 | 2.5 | 6 | 9.64 | 10 | 13 | 0.8 | 0.8 | 12.2 | ISO 21670 |
| M8x1 | 1 | 2.7 | 1 | 9.5 | 22.5 | 13.6 | 2.5 | 6 | 9.64 | 10 | 13 | 0.8 | 0.8 | 12.2 | ISO 21670 |
| M10 | 1.5 | 2.95 | 1.2 | 11.5 | 26.5 | 16.9 | 3 | 7 | 12.57 | 13 | 16 | 1 | 1 | 21.8 | ISO 21670 |
| M10x1.25 | 1.25 | 2.95 | 1.2 | 11.5 | 26.5 | 16.9 | 3 | 7 | 12.57 | 13 | 16 | 1 | 1 | 21.8 | ISO 21670 |
| M10x1 | 1 | 2.95 | 1.2 | 11.5 | 26.5 | 16.9 | 3 | 7 | 12.57 | 13 | 16 | 1 | 1 | 21.8 | ISO 21670 |
| M12 | 1.75 | 3.2 | 1.2 | 14 | 30.5 | 19.4 | 3 | 8 | 14.57 | 15 | 18 | 1 | 1.2 | 29.4 | ISO 21670 |
| M12x1.5 | 1.5 | 3.2 | 1.2 | 14 | 30.5 | 19.4 | 3 | 8 | 14.57 | 15 | 18 | 1 | 1.2 | 29.4 | ISO 21670 |
| M12x1.25 | 1.25 | 3.2 | 1.2 | 14 | 30.5 | 19.4 | 3 | 8 | 14.57 | 15 | 18 | 1 | 1.2 | 29.4 | ISO 21670 |
| M14 | 2 | 3.45 | 1.2 | 16 | 33.5 | 22.4 | 4 | 8 | 16.16 | 17 | 21 | 1 | 1.2 | 45.8 | ISO 21670 |
| M14x1.5 | 1.5 | 3.45 | 1.2 | 16 | 33.5 | 22.4 | 4 | 8 | 16.16 | 17 | 21 | 1 | 1.2 | 45.8 | ISO 21670 |
| M16 | 2 | 3.7 | 1.2 | 18 | 36.5 | 25 | 4 | 8 | 18.66 | 19.5 | 24 | 1 | 1.2 | 63.1 | ISO 21670 |
| M16x1.5 | 1.5 | 3.7 | 1.2 | 18 | 36.5 | 25 | 4 | 8 | 18.66 | 19.5 | 24 | 1 | 1.2 | 63.1 | ISO 21670 |
Equivalent Standards
Where direct equivalents exist (ISO ↔ DIN, ISO ↔ ASME), they are listed on the parent Hex Weld Nuts with Flange page.
Always confirm against the dimensions on this page, since some "equivalent" standards differ in tolerances and head geometry.
When to Specify ISO 21670
Choose ISO 21670 for international engineering work and OEM supply where ISO standards are the contractual reference. It is the default modern specification for hex weld nuts with flange.
Custom manufacturing · Made to drawing
Need a nut to this standard in a non-standard size?
Parts built to ISO 21670 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.
