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Pipe Nut Dimensions (DIN 431, G1/8 to G4)
Guide · Updated October 28, 2026
DIN 431 covers hexagon pipe nuts with G thread (ISO 228-1), from G1/8 to G4. The values agree across Fuller Fasteners, Ferrobend, fasteners.eu and Swiss Fittings (cast). Check your supplier for critical work.
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Step by step
- Identify the thread: DIN 431 uses parallel G pipe thread (ISO 228-1), not metric thread.
- Check the SW: G1/8, G1/4, G1/2 and G5/8 come in two wrench sizes, so the designation names the SW.
- Pick the wrench: Use s from the chart.
- Seal separately: G thread does not seal on the thread, so use a washer or O-ring.
- Tighten: Pipe nuts are thin, so do not overload them.
DIN 431 pipe nut dimensions (mm)
Columns: G thread size, width across flats s, alternate s, height m (nominal), width across corners e min.
- Size | s | alt s | m | e min
- G1/8 | 18 | 19 | 6 | 19.85
- G1/4 | 21 | 22 | 6 | 22.78
- G3/8 | 27 | n/a | 7 | 29.56
- G1/2 | 34 | 32 | 8 | 37.29
- (G5/8) | 34 | 32 | 8 | 37.29
- G3/4 | 36 | n/a | 9 | 39.55
- (G7/8) | 41 | n/a | 9 | 45.2
- G1 | 46 | n/a | 10 | 50.85
- (G1 1/8) | 50 | n/a | 10 | 55.37
- G1 1/4 | 55 | n/a | 11 | 60.79
- G1 1/2 | 60 | n/a | 12 | 66.44
- G2 | 75 | n/a | 13 | 82.6
- G2 1/2 | 95 | n/a | 16 | —
- G3 | 105 | n/a | 19 | —
- G4 | 135 | n/a | 22 | —
Worked example: G1/2 pipe nut
A G1/2 DIN 431 nut is 8 mm thick with a 34 mm hex, or 32 mm on the SW32 version. Order it as "DIN 431 A G1/2 SW34" so you get the right wrench size.
Common problems
- Will not thread on: the fitting is metric or NPT, not G.
- Wrong wrench: check SW 32 vs 34.
- Leaks: G thread needs a sealing washer.
FAQ
What is DIN 431?
The thin hexagon pipe nut with G (BSPP) parallel thread, used as a locknut on pipe and conduit.
Why two wrench sizes?
DIN 431 allows two SW sizes for G1/8, G1/4, G1/2 and G5/8, and the designation must state which one (for example SW34).
Why is e dashed above G2?
Only one table gives e for those sizes.
What about G5 and G6?
Those are octagon type B nuts, and only one table lists them, so they are not charted.
Note on sources
One web table has a shifted m min column. m here is the nominal value agreed by Fuller, Ferrobend, Swiss Fittings and the m max values in that table.
Related guides and calculators
- Hex head screw plugs (DIN 910)
- Socket screw plugs (DIN 908)
- Turnbuckle nuts (DIN 1479)
- Hex nuts (ISO 4032)
- Hex coupling nuts (DIN 6334)
- Knurled thumb nuts, thin (DIN 467)
- Wrench size chart
- All free machinist calculators
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