Hex Flange Bolts manufactured to DIN 6921 follow a specific scope. This page summarizes that scope, lists every dimension the standard fixes, and points to the most common cross-references.
DIN 6921 — Scope
DIN 6921 specifies the dimensions and tolerances of hex flange bolts. 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
DIN 6921, alongside the related ISO 1665 / DIN 6921 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 DIN 6921
| Size | Pitch (mm) | Flange diameter dc (mm) | Head height k (mm) | Width across flats s (mm) | Reference standard |
|---|---|---|---|---|---|
| M5 | 0.8 | 11.8 | 4.7 | 8.0 | ISO 1665 / DIN 6921 |
| M6 | 1.0 | 14.2 | 5.6 | 10.0 | ISO 1665 / DIN 6921 |
| M8 | 1.25 | 17.9 | 7.2 | 13.0 | ISO 1665 / DIN 6921 |
| M10 | 1.5 | 21.8 | 8.9 | 15.0 | ISO 1665 / DIN 6921 |
| M12 | 1.75 | 26.0 | 10.7 | 18.0 | ISO 1665 / DIN 6921 |
| M14 | 2.0 | 29.9 | 12.3 | 21.0 | ISO 1665 / DIN 6921 |
| M16 | 2.0 | 34.5 | 14.1 | 24.0 | ISO 1665 / DIN 6921 |
| M20 | 2.5 | 42.8 | 17.5 | 30.0 | ISO 1665 / DIN 6921 |
| M24 | 3.0 | 51.1 | 21.0 | 36.0 | ISO 1665 / DIN 6921 |
Equivalent Standards
Where direct equivalents exist (ISO ↔ DIN, ISO ↔ ASME), they are listed on the parent Hex Flange Bolts page. Always confirm against the dimensions on this page, since some "equivalent" standards differ in tolerances and head geometry.
Companion Standards
DIN 6921 controls only the geometry of hex flange bolts. The mechanical strength is set by ISO 898-1 (bolts and screws) or ISO 898-2 (nuts); the surface finish is governed by separate finish standards (e.g. ISO 4042 for electroplating). For corrosion testing, the relevant document is ISO 9227 (neutral salt spray).