DIN 6923 Hexagon Flange Nut
German designation for the flange nut, superseded on new drawings by the harmonised EN 1661. Dimensions track ISO 4161 to within a few tenths of a millimetre across M5–M20, so the two are treated as interchangeable in practice — but the flange replaces a washer, so check the bearing surface is wide enough before dropping a plain nut in its place.
Where it is used
The flange nut replaces a nut and washer with a single part: a hex nut with a wide circular flange formed into the base. It is used where the bearing area matters — thin sheet, aluminium, composites and slotted holes — and where the assembly time saved by dropping a separate washer has value.
How to choose it
Common property classes are 8 and 10, matched to the bolt grade in the usual way. The flange is available with or without serrations: the serrated face bites into the workpiece and resists loosening better, but it marks the surface and is usually specified only where the joint is not taken apart. On sheet under about 3 mm the plain nut being replaced concentrates load on roughly 60% of the area, which is often enough to dimple the panel and lose preload after the first thermal cycle.
Dimensions8 sizes · millimetres
| Thread d | Pitch P (mm) | Width across flats s (mm) | Flange diameter dc (mm) | Nut height m (mm) |
|---|---|---|---|---|
| M5 | 0.8 | 8 | 11.8 | 5 |
| M6 | 1 | 10 | 14.2 | 6 |
| M8 | 1.25 | 13 | 17.9 | 8 |
| M10 | 1.5 | 15 | 21.8 | 10 |
| M12 | 1.75 | 16 | 26 | 12 |
| M14 | 2 | 18 | 29.6 | 14 |
| M16 | 2 | 24 | 31.9 | 16 |
| M20 | 2.5 | 30 | 42.8 | 20 |
Nominal dimensions in millimetres as published in DIN 6923. Tolerances, material requirements and marking are defined separately by the issuing body.
Available sizeslinked to individual specification pages
Thread referencesused by the sizes above
Fitting and interchange notes
Dimensionally interchangeable with ISO 4161 to within a few tenths of a millimetre across M5–M20, and superseded on new drawings by the harmonised EN 1661. Do not stack a flat washer under a flange nut: the flange is the washer, and adding one changes the effective friction radius the tightening torque was calculated for. When replacing a flange nut with a plain nut, add a washer of at least the flange diameter or the bearing pressure rises well above what the joint was designed for.