Specifications
Surface Treatments
Certifications
- ISO 9001 - 2015 Certified
- PED 2014/68/EC
- NACE MR0175/ISO 15156-2
- NORSOK M-650
- DFAR
- MERKBLATT AD 2000 W2/W7/W10
Incoloy 800H Coupling Nuts
Incoloy 800H coupling nuts to DIN 6334 are extended-hex nuts used to join two lengths of Incoloy 800H threaded rod end-to-end or to extend a stud bolt with a continuation rod. TorqBolt machines coupling nuts from ASTM B408 round bar in diameter range M12 to M48 with nut length per DIN 6334 (typically 3d nut length for full thread engagement on both joined rods). The hex across-flats matches the standard DIN 934 hex nut schedule for the same thread diameter, with extended nut length providing 1.5d thread engagement on each joined rod. Internal threads are tapped to class 6H per ISO 965 (metric) or class 2B per ASME B1.1 (inch). Every coupling nut ships with EN 10204 type 3.1 mill test certificate documenting heat number, ASTM B408 chemistry, solution-anneal cycle and ASTM grain size 5 verification. Coupling nuts are the standard solution for field-splicing threaded rod on hot-zone hanger and support construction without welding.
Coupling Nut Dimensions (DIN 6334)
| Size designation | Across flats / OD | Head / nut height | Thread pitch | Standard reference |
|---|---|---|---|---|
| M12 | 12.0 mm thread | A/F 19 mm; Nut length 36 mm (3d) | 1.75 mm | DIN 6334 |
| M16 | 16.0 mm thread | A/F 24 mm; Nut length 48 mm (3d) | 2.0 mm | DIN 6334 |
| M20 | 20.0 mm thread | A/F 30 mm; Nut length 60 mm (3d) | 2.5 mm | DIN 6334 |
| M24 | 24.0 mm thread | A/F 36 mm; Nut length 72 mm (3d) | 3.0 mm | DIN 6334 |
| M30 | 30.0 mm thread | A/F 46 mm; Nut length 90 mm (3d) | 3.5 mm | DIN 6334 |
| M36 | 36.0 mm thread | A/F 55 mm; Nut length 108 mm (3d) | 4.0 mm | DIN 6334 |
| M42 | 42.0 mm thread | A/F 65 mm; Nut length 126 mm (3d) | 4.5 mm | DIN 6334 |
| M48 | 48.0 mm thread | A/F 75 mm; Nut length 144 mm (3d) | 5.0 mm | DIN 6334 |
Manufacturing Route at TorqBolt
Coupling nut manufacture is a CNC turn-mill operation with extended through-hole tapping for the 3d nut length:
- Receive Incoloy 800H bar to ASTM B408; PMI verification.
- Cut bar into 3d-length slugs (M12 = 36 mm, M48 = 144 mm).
- CNC mill the 6-sided hex profile per DIN 6334 (matches DIN 934 across-flats).
- Drill the through-hole to thread-tap minor diameter; controlled straightness over extended length.
- Tap the internal thread to class 6H per ISO 965 (metric) over full nut length; thread plug full-traverse verification.
- Solution anneal at 1149 deg C plateau followed by rapid quench; ASTM grain size 5 verified.
- Hardness band 120-184 HB on first piece and one per batch.
- Visual + dimensional + PMI inspection 100 percent; verify both ends of thread for chamfer integrity.
- Pack matched with threaded rod or stud bolt extensions; CoC + EN 10204 cert.
Coupling Nut Sizes Stocked and Lead Times
| Diameter range | Length range | Stock status | Lead time |
|---|---|---|---|
| M12 - M20 | Per DIN 6334 | Stock + ex-stock | 10 working days |
| M24 - M30 | Per DIN 6334 | Made-to-order from stock bar | 14 to 18 working days |
| M36 - M42 | Per DIN 6334 | Made-to-order from stock bar | 3 to 4 weeks |
| M48 | Per DIN 6334 | Made-to-order, large bar | 4 to 6 weeks |
Inspection and Heat Marking
Coupling nut specific inspections cover through-bore straightness, full-length thread engagement and both-end chamfer integrity:
- Through-bore straightness verified to ensure plug gauge full-traverse.
- Internal thread verified with class 6H plug gauge from both ends.
- Nut length verified to DIN 6334 schedule (3d minimum).
- Across-flats verified per DIN 934 schedule.
- Hardness band 120-184 HB on first piece and one per batch.
- ASTM E112 grain-size etch verification.
- PMI by X-ray fluorescence on first piece and one per batch.
- Both-end chamfer integrity verified for thread start.
Typical Service Conditions
Coupling nuts are specified for field-splicing threaded rod and extending stud bolts on hot-zone support and hanger construction:
- Threaded rod splicing on long-span hanger construction.
- Anchor bolt extension where field length exceeds shop one-piece capability.
- Stud bolt extension on heat-exchanger tubesheet bolting.
- Heat exchanger tube-bundle support hanger construction.
- Furnace component retort hanger and support rod splicing.
- Reformer pigtail support hanger construction with field-spliced rods.
Incoloy 800H Alloy Considerations on This Fastener Form
Companion Fasteners and Related Pages
- Threaded Rod: matched threaded rod for coupling nut joints.
- Hex Nuts: standard nut for terminating spliced assemblies.
- Heavy Hex Nuts: heavy-pattern alternative for high-load splices.
- Lock Nuts: prevailing-torque jam-nut alternative.
- All-Thread Bar: continuous all-thread alternative for long-span construction.
Frequently Asked Questions
Q. What is the standard nut length for coupling nuts?
DIN 6334 specifies 3d nut length (M12 = 36 mm, M24 = 72 mm). This provides 1.5d thread engagement on each joined rod for full load transfer. Shorter coupling nuts (2d) are supplied on PO call-out for restricted-clearance applications.
Q. Are coupling nuts available in inch sizes?
Yes. ASME B18.2.4 hex coupling nuts 1/4 inch through 1-1/2 inch are machined on PO call-out from B408 bar with class 2B UNC internal threads.
Q. Can coupling nuts be used to join two different bolt diameters?
No. Standard coupling nuts have one internal thread size from end to end. Adapter / reducer couplings (different thread each end) are machined to print on special order.
Q. Is the coupling-nut joint as strong as the rod itself?
Yes when 1.5d minimum thread engagement is achieved on each joined rod. DIN 6334 3d nut length provides this margin. The joint strength is governed by the rod material; thread shear is not the limiting failure mode.
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