Home » Hexagonal Stud Connector Nuts (DIN 6334) - Marine Stainless Steel (A4)

Hexagonal Stud Connector Nuts (DIN 6334) - Marine Stainless Steel (A4)

Hexagonal Stud Connector Nuts (DIN 6334) — Marine Stainless Steel A4 (SUS316)

FULLERKREG DIN 6334 hexagonal long coupling nuts in A4 marine-grade stainless steel (SUS316 / 1.4401) are the premium choice for demanding environments where superior corrosion resistance is essential. Conforming to the DIN 6334 standard, the nut length is exactly 3 times the nominal thread diameter (3×d), providing the extended thread engagement required to reliably join two threaded rods, studs, or anchor bolts end-to-end. The passivated (acid-washed) bright surface finish maximises corrosion resistance and ensures a clean, oxide-free appearance. The addition of 2–3% molybdenum in SUS316 delivers significantly enhanced resistance to chloride-induced pitting and crevice corrosion compared to standard A2 (SUS304), making these coupling nuts the correct specification for marine, offshore, coastal architectural, chemical processing, and food-grade applications. Available in thread sizes M3 through M56.

Dimensional Data

All dimensions in mm. Nut length m = 3×d (DIN 6334). Tolerances per ISO 4034 / DIN 6334. Unit weight (g) is theoretical reference value for SUS316 (density 7.98 g/cm³).

Thread
d		 Pitch
(mm)		 Nut Length
m = 3×d (mm)		 Across Flats
s (mm)		 Across Corners
e min (mm)		 Unit Weight
(g/pc)
M3 0.5 9.0 5.50 6.01 ~0.7
M4 0.7 12.0 7.00 7.66 ~1.6
M5 0.8 15.0 8.00 8.79 ~2.9
M6 1.0 18.0 10.00 11.05 ~5.1
M8 1.25 24.0 13.00 14.38 ~10.6
M10 1.5 30.0 16.00 17.77 ~19.7
M12 1.75 36.0 18.00 20.03 ~32.3
M14 2.0 42.0 22.00 24.49 ~55.5
M16 2.0 48.0 24.00 26.75 ~78.8
M18 2.5 54.0 27.00 29.56 ~109
M20 2.5 60.0 30.00 32.95 ~149
M22 2.5 66.0 32.00 35.03 ~187
M24 3.0 72.0 36.00 39.55 ~257
M27 3.0 81.0 41.00 45.20 ~383
M30 3.5 90.0 46.00 50.85 ~524
M33 3.5 99.0 50.00 55.37 ~685
M36 4.0 108.0 55.00 60.79 ~897
M39 4.0 117.0 60.00 66.44 ~1159
M42 4.5 126.0 65.00 71.30 ~1441
M45 4.5 135.0 70.00 76.95 ~1774
M48 5.0 144.0 75.00 82.60 ~2146
M52 5.0 156.0 80.00 88.25 ~2671
M56 5.5 168.0 85.00 93.56 ~3256

* Nut length m = 3×d per DIN 6334. Across Corners (e) calculated from s × 1.155. Unit weights are theoretical reference values for SUS316 (density 7.98 g/cm³); actual weights may vary ±5%. Sizes M39 and above may have longer lead times — please enquire.

Selection Guide

Parameter Specification
Standard DIN 6334
Also Known As Long Hex Nut, Coupling Nut, Extension Nut, Stud Connector Nut, Barrel Nut
Material Marine Stainless Steel A4 (SUS316 / 1.4401)
Surface Treatment Acid-washed (Passivated / Bright Finish)
Nut Length 3×d (three times nominal thread diameter)
Thread Type Metric coarse thread (ISO 68-1)
Thread Tolerance 6H
Property Class A4-70 (per ISO 3506-2)
Thread Size Range M3 – M56
Tensile Strength ≥ 700 MPa
Hardness 147–220 HV
Pitting Resistance (PRE) ≥ 24 (Mo-bearing grade)
Operating Temperature -200°C to +400°C
Magnetic Non-magnetic (annealed condition)
RoHS Compliant Yes
Packaging Bulk bag / box; custom packaging available

Standard Notes

DIN 6334 specifies hexagonal long nuts with a length equal to 3 times the nominal thread diameter (m = 3×d). This extended length provides significantly greater thread engagement than a standard hex nut, making DIN 6334 coupling nuts the correct choice for joining two externally threaded components — such as threaded rods, studs, or anchor bolts — end-to-end. The A4 (SUS316) grade adds 2–3% molybdenum to the A2 composition, significantly improving resistance to chloride-induced pitting and crevice corrosion, making it the preferred specification for marine, offshore, and chemical environments.

  • DIN 6334 — Hexagon long nuts, metric coarse thread, length = 3×d
  • Equivalent / related standards: ISO 4033 (hex high nuts), EN 14399-3 (structural)
  • Material grade: A4 per ISO 3506-2 (SUS316 / 1.4401)
  • Surface: Passivated (acid-washed bright finish) — no additional coating
  • Thread: Right-hand, metric coarse, tolerance class 6H
  • Key advantage vs A2: Molybdenum addition provides superior chloride and pitting corrosion resistance — essential for marine and chemical environments
  • Typical applications: Marine hardware, offshore structures, coastal architecture, chemical plant piping, food processing equipment, swimming pool structures, desalination plant fastening

A4 vs A2 — When to Specify Marine Grade Coupling Nuts

Application Environment Recommended Grade
Indoor / dry / light corrosion A2 (SUS304)
Marine / coastal / saltwater exposure A4 (SUS316) ✓
Chemical processing / acids / chlorides A4 (SUS316) ✓
Food & beverage / pharmaceutical A4 (SUS316) ✓
Offshore / subsea structures A4 (SUS316) ✓
Swimming pools / desalination A4 (SUS316) ✓
Coastal architectural / facade A4 (SUS316) ✓

DIN 6334 vs Standard Hex Nut — Thread Engagement Comparison

Nut Type Standard Nut Length Thread Engagement Typical Use
Standard Hex Nut DIN 934 / ISO 4032 ~0.8×d Short Single bolt/stud fastening
High Hex Nut ISO 4033 ~0.9×d Medium Higher load single fastening
Long Coupling Nut DIN 6334 3×d Full engagement both ends Rod-to-rod / stud-to-stud joining ✓

Product Gallery

DIN 6334 Hexagonal Long Coupling Nuts — Marine Stainless Steel A4 (SUS316) actual product photos:

[ Photo 1 ] [ Photo 2 ] [ Photo 3 ] [ Photo 4 ]

Chemical Composition — A4 Marine Stainless Steel (SUS316 / 1.4401)

Grade C (%) Si (%) Mn (%) P (%) S (%) Cr (%) Ni (%) Mo (%)
SUS316 (A4) ≤ 0.08 ≤ 1.00 ≤ 2.00 ≤ 0.045 ≤ 0.030 16.0–18.0 10.0–14.0 2.0–3.0

* The molybdenum (Mo) content is the key differentiator from A2/SUS304, providing significantly enhanced resistance to pitting and crevice corrosion in chloride-containing environments. PRE (Pitting Resistance Equivalent) = Cr + 3.3×Mo ≥ 24.

Mechanical Properties — A4-70 (ISO 3506-2)

Property Class Proof Load Stress (MPa) Tensile Strength (MPa) Hardness (HV) Min. Elongation
A4-70 ≥ 500 ≥ 700 147–220 ≥ 40%

Why Choose FULLERKREG DIN 6334 Marine Coupling Nuts?

  • 🏭 Factory Direct — Manufactured in-house with full process control from raw material to finished part
  • 🌊 Mo-Bearing Marine Grade — SUS316 with 2–3% Mo delivers superior chloride and pitting corrosion resistance vs standard A2; PRE ≥ 24
  • 🔗 Full Thread Engagement Both Ends — 3×d length ensures maximum load transfer when joining two threaded rods or studs in marine and structural applications
  • 📐 Strict DIN 6334 Compliance — Length precisely 3×d; every dimension and tolerance verified against the standard
  • 🔬 Material Certified — Mill test certificates (MTC) available; SUS316 Mo content verified by spectrometer
  • 📏 Wide Size Range — M3 through M56 in stock; covers precision instruments to heavy offshore structural applications
  • 🌡️ Extended Temperature Range — Reliable performance from -200°C to +400°C; suitable for cryogenic and elevated-temperature applications
  • 📦 Bulk Wholesale Supply — MOQ-friendly pricing tiers; consistent lot quality for production lines
  • 🚢 Global Export Experience — Shipped worldwide with proper export documentation and packaging
  • 💬 Technical Support — Engineering team available for application guidance, custom lengths, and special requirements

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