Coupling Nut
Nuts · extension nut · long nut · rod coupling nut
Definition: A coupling nut is an extra-long hex nut used to join two threaded rods or bolts end to end, or to extend a stud.
Anatomy & Schematic
■ Body■ Internal thread
Governing standards: ASME B18.2.2
Common Sizes
| Inch | Metric | Head width | Head height |
|---|---|---|---|
| 1/4-20 | M6 | 7/16 | 3/4–2 long |
| 3/8-16 | M10 | 9/16 | 1–3 long |
| 1/2-13 | M12 | 3/4 | 1–4 long |
Representative sizes. Full dimensional data lives in the standards listed below.
Grades & Strength
| Grade | Material | Tensile (psi) | Marking |
|---|---|---|---|
| Zinc steel | carbon steel, zinc-plated | — | None |
| Stainless | 304 stainless | — | None |
Materials
- Zinc-plated steel
- Stainless steel
- Brass
Pros & Cons
Pros
- Joins rods without welding
- Strong, wrench-friendly body
- Readily available
Cons
- Adds a bulky joint
- Not for high-vibration unless locked
- Thread alignment matters on both ends
Typical Uses
- Joining threaded rods end to end
- Extending hanger rods
- Furniture leg leveling
- Custom-length fasteners
Alternatives & Related
- Hex Nut — Short nut for a single fastening
- Threaded Rod — The rod a coupling nut joins
Where to Buy
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FAQ
What is a coupling nut used for?
Joining two threaded rods end to end, extending a rod, or leveling — common in hanging systems and furniture feet.
How much rod should thread into a coupling nut?
At least one full nut diameter of engagement on each end for full strength.