Specification summary of DIN 7991 as applied to countersunk socket screws: the dimensions the standard controls, the tolerance and product grades it defines, the full specified size range, and the equivalent DIN/ISO/ASME designations.
DIN 7991 — Scope
DIN 7991 specifies the dimensions and tolerances of countersunk socket screws. 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 7991, alongside the related ISO 10642 / DIN 7991 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 7991
| Size | Pitch (mm) | Head diameter dk (mm) | Head height k (mm) | Hex key s (mm) | Countersink angle (deg) | Reference standard |
|---|---|---|---|---|---|---|
| M3 | 0.5 | 6.72 | 1.86 | 2.0 | 90 | ISO 10642 / DIN 7991 |
| M4 | 0.7 | 8.96 | 2.48 | 2.5 | 90 | ISO 10642 / DIN 7991 |
| M5 | 0.8 | 11.2 | 3.1 | 3.0 | 90 | ISO 10642 / DIN 7991 |
| M6 | 1.0 | 13.44 | 3.72 | 4.0 | 90 | ISO 10642 / DIN 7991 |
| M8 | 1.25 | 17.92 | 4.96 | 5.0 | 90 | ISO 10642 / DIN 7991 |
| M10 | 1.5 | 22.4 | 6.2 | 6.0 | 90 | ISO 10642 / DIN 7991 |
| M12 | 1.75 | 26.88 | 7.44 | 8.0 | 90 | ISO 10642 / DIN 7991 |
| M14 | 2.0 | 30.0 | 8.4 | 10.0 | 90 | ISO 10642 / DIN 7991 |
| M16 | 2.0 | 33.6 | 9.3 | 10.0 | 90 | ISO 10642 / DIN 7991 |
| M20 | 2.5 | 40.32 | 11.2 | 12.0 | 90 | ISO 10642 / DIN 7991 |
| M24 | 3.0 | 47.04 | 13.0 | 14.0 | 90 | ISO 10642 / DIN 7991 |
Equivalent Standards
Where direct equivalents exist (ISO ↔ DIN, ISO ↔ ASME), they are listed on the parent Countersunk Socket Screws page. Always confirm against the dimensions on this page, since some "equivalent" standards differ in tolerances and head geometry.
Companion Standards
DIN 7991 controls only the geometry of countersunk socket screws. 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).