Size picker · Flange nut · DIN 6923
Flange nut sizes.
The nut with the washer built in. Pick a diameter for the spanner size, the flange diameter, the height and the pitch — and check which standard yours is, because the two in circulation disagree on the spanner.
1 Pick a diameter
2 Serrated or plain?
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Drawn to proportion from the standard dimensions. Illustration, not a photograph of the item.
Selected
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| Sym | Dimension | Value |
|---|
Job stopped? Ring 01327 877577 and we'll check the stock while you're on.
Read the full nut size chart
| Size | Pitch | s — across flats | m — height | dc — flange, max | c — flange thickness | ISO 4161 differs |
|---|---|---|---|---|---|---|
| 0.7 | ask us | ask us | ask us | ask us | — | |
| 0.8 | 8 | 5 | 11.8 | 1 | — | |
| 1 | 10 | 6 | 14.2 | 1.1 | — | |
| 1.25 | 13 | 8 | 17.9 | 1.2 | — | |
| 1.5 | 15 | 10 | 21.8 | 1.5 | s 16 (EN 1661) | |
| 1.75 | 18 | 12 | 26 | 1.8 | — | |
| 2 | 21 | 14 | 29.9 | 2.1 | — | |
| 2 | 24 | 16 | 34.5 | 2.4 | — | |
| 2.5 | 30 | 20 | 42.8 | 3 | — |
Figures are the standards' nominal dimensions, each confirmed against two independent published tables — anything we could only source once reads "ask us" rather than printing a number we can't stand behind. Odd diameters like M7 and M9, left-hand threads and the finer pitches are all made, and availability varies by finish and class — ask us for anything you can't see.Figures are the standards' nominal dimensions, each confirmed against two independent published tables. Where only one table prints a figure, where two disagree, or where nobody publishes one at all, the row reads "ask us" rather than a number we can't stand behind. Imperial washers (BS 3410), the other BS 4320 forms, spring and shakeproof patterns and the hardness grades are all real too, and availability varies by finish — ask us for anything you can't see.
Two standards, two spanners
A flange nut spreads the load and usually has a serrated face that resists shaking loose, which saves you a washer. Watch the spanner size: M10 flange nuts are 15mm across flats under DIN 6923, and 16mm under DIN EN 1661 which replaced it. Both are sold, so the table above prints both wherever they differ.
No source publishes an across-corners figure for a flange nut, so that row is absent here rather than filled with a number nobody stands behind.
Which class of nut for which bolt
A nut is not graded like a bolt. It carries a single number — its proof load class — and the rule is simple: the nut class is the digit to the left of the bolt class. A class 8 nut for an 8.8 bolt, class 10 for a 10.9, class 12 for a 12.9. Put a class 6 nut on a 10.9 bolt and the nut strips before the bolt reaches its rating, which is exactly the failure you do not want.
Stainless works differently again. On a stainless bolt the number is a tenth of the tensile strength, so A4-80 means 800 MPa. On a stainless nut it is a tenth of the proof load, and the standard's partner for an A4-80 bolt is an A4-70 nut — A4-80 is not a nut designation at all, however often you hear it asked for.
Not sure which you need?
Bring the old one in, or send us a photo. We are on Baird Close in Daventry with metric and imperial stock across the common classes and finishes.
More size charts
Every size, drawn to scale.
Hex setscrews
DIN 933 · full thread
Hex bolts
DIN 931 · part thread
Socket cap screws
DIN 912
Low head cap screws
DIN 7984
Button head screws
ISO 7380-1
Flanged button heads
ISO 7380-2
Countersunk socket screws
DIN 7991
Grub screws
DIN 913–916 · five points
Nuts
DIN 934 · nyloc · thin · Stover · flange
Washers
ISO 7089 · BS 4320 · penny
Not sure what the markings on the head mean? Bolt grades explained covers 8.8, 10.9, 12.9, stainless A2 and A4, and the imperial SAE grades.
All of it comes off the shelf at Baird Close — see the full fasteners & fixings range, or every size guide.