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Hex Coupling Nut Dimensions (DIN 6334, 3d Long, M6 to M36)
Guide · Updated October 28, 2026
DIN 6334 covers hexagon coupling nuts (long nuts), length m = 3d, from M6 to M36. Pitch, s and m agree across the Dueemme DIN 6334 sheet, fasteners.eu and the Westfield Fasteners datasheet (M6 to M30). Check your supplier for critical work.
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Step by step
- Match the rod: Check the threaded rod size and coarse pitch.
- Pick the wrench: Use the width across flats s from the chart.
- Mark the centre: Mark both rods at m/2 so each one engages half the nut.
- Thread both ends: Run each rod in to the mark.
- Lock if needed: Add jam nuts (ISO 4035) on each side.
DIN 6334 hex coupling nut dimensions (mm)
Columns: thread, pitch P, width across flats s, length m.
- Size | P | s | m
- M6 | 1 | 10 | 18
- M8 | 1.25 | 13 | 24
- M10 | 1.5 | 17 | 30
- M12 | 1.75 | 19 | 36
- M14 | 2 | 22 | 42
- M16 | 2 | 24 | 48
- M18 | 2.5 | 27 | 54
- M20 | 2.5 | 30 | 60
- M22 | 2.5 | 32 | 66
- M24 | 3 | 36 | 72
- M27 | 3 | 41 | 81
- M30 | 3.5 | 46 | 90
- M33 | 3.5 | 50 | 99
- M36 | 4 | 55 | 108
Worked example: M12 rod splice
An M12 DIN 6334 coupling nut is 36 mm long with a 19 mm hex. Mark each rod at 18 mm and thread both ends to the mark, so each rod engages a full 1.5d.
Common problems
- Uneven engagement: mark the centre first.
- Nut loosens: add ISO 4035 jam nuts.
- Wrong wrench: M10 is 17 mm, not 16.
FAQ
What is DIN 6334?
The hexagon coupling nut, or long nut. Its length is 3 times the thread diameter, and it joins two threaded rods.
Why no width across corners e?
Only one table family gives e, and Westfield lists different e values, so the column is skipped.
Is M5 covered?
Westfield lists M5 (s 8, m 15), but no second source confirms it, so it is not charted.
Thread tolerance?
6H internal metric coarse thread.
Strength?
Property class 6, 8 or 10, or stainless A2 or A4.
Related guides and calculators
- Tube turnbuckles (DIN 1478)
- Forged turnbuckles (DIN 1480)
- Turnbuckle nuts (DIN 1479)
- Pipe nuts (DIN 431)
- Slotted round nuts (DIN 546)
- Wing nuts (DIN 315)
- Jam nuts (ISO 4035)
- Hex nuts (ISO 4032)
- High hex nuts (ISO 4033)
- Wrench size chart
- All free machinist calculators
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General shop information only — follow your drawing, tool maker's data and your quality system.