DIYUK DIN 6334 Hex Coupling Nuts, BZP Bright Zinc Plated Steel Threaded Rod Connector, Long Nut, Studding Extension, M5-M24, Packs of 2-100

DIN 6334 hex coupling nuts (also known as long nuts, extension nuts or connecting nuts): an elongated hexagon nut with a body length of three times the nominal thread diameter (3d) from M6 to M24 (25mm on the M5), used to join two lengths of the same metric threaded rod or stud into one continuous connection. The extended body lets two separate rod ends wind in from opposite sides and meet centrally inside the nut, turning two lengths of studding into a single rigid, in-line run.

The extra length compared with a standard hex nut gives significantly more thread engagement than a standard nut of the same diameter, spreading the load over a longer run of thread and increasing the tensile capacity of the joint. The nut body is manufactured from steel in property class 6 and finished in bright zinc plating (BZP), giving general-purpose corrosion resistance.

The hexagon profile allows tightening from either end with a standard open-end or socket spanner, so two rod ends can be wound in from opposite sides and torqued up against one another inside the nut, or a single continuous length of studding can be joined mid-run. In effect, a single coupling nut does the job that would otherwise need a full-length replacement rod, letting a shorter offcut or a second length of the same threaded rod be pressed into service.

Key Features

• DIN 6334 hexagon coupling nut, also known as a long nut, extension nut or connecting nut, for joining threaded rod of the same metric diameter
• Extended body length of three times the nominal thread diameter (3d) from M6 to M24 (25mm on the M5), giving significantly more thread engagement than a standard hex nut of the same size
• Steel construction in property class 6
• Bright zinc plated (BZP) finish for general-purpose corrosion resistance
• Full hexagon profile allows tightening from either end with a standard open-end or socket spanner
• Full-length internal thread lets two rod ends be wound in from opposite sides to meet centrally, or joins a continuous run of studding mid-length
• Nine sizes from M5 up to M24 for metric threaded rod used in construction and engineering, in packs of 2, 5, 10, 25, 50 or 100

Choosing the Right Size

Match the coupling nut to the nominal diameter of the threaded rod being joined: an M10 rod needs an M10 coupling nut, and so on. Use the width across flats figure in the table below to check which spanner or socket size you will need before starting work, and the length figure to confirm the nut will fit the available space if the rod is being joined inside a confined void, duct or ceiling grid.

Specification

Installation Guidance

Select the coupling nut that matches the nominal diameter of the threaded rod or stud being joined; thread size and pitch must match on both pieces of rod for the joint to draw up correctly. The internal thread runs the full length of the nut, so each rod is wound in from its own end until the two meet centrally inside the nut body; because the nut body is three times the thread diameter in length (25mm on the M5), there is enough working length to wind each rod in comfortably before the joint is fully engaged.

• Aim for at least one full diameter of thread engagement on each side of the joint for a secure, load-bearing connection
• Apply a thread-locking compound before assembly if a permanent joint is required
• Tighten using a standard open-end or socket spanner across the hex flats; the nut can be held or turned from either end
• When joining two separate lengths of studding, wind both rods in evenly so the joint sits centrally inside the nut rather than loaded to one end

Typical Applications

• Extending threaded rod (studding) runs in suspended ceiling grids where a single length doesn’t reach the required drop
• Cable tray, containment and basket systems where threaded drop rods need to be lengthened or joined mid-run
• HVAC pipe and duct hangers, joining sections of support rod to reach the required suspension height
• Joining anchor bolts, tie rods and fixings in steel fabrication and racking assemblies
• General engineering, machinery guarding and adjustable furniture assembly wherever a rigid, in-line connection between two lengths of the same threaded rod is required
• Keeping a range of sizes on hand as a general-purpose spare for ad-hoc studding repairs and extensions on site

Common Questions

What is a coupling nut?
A coupling nut, also called a long nut, extension nut or connecting nut, is an elongated hexagon nut threaded along its full length. Two lengths of the same metric threaded rod or stud wind in from opposite ends and meet inside it, joining them into one straight run.

What sizes are available?
Nine sizes (thread diameter x length): M5 x 25mm, M6 x 18mm, M8 x 24mm, M10 x 30mm, M12 x 36mm, M14 x 42mm, M16 x 48mm, M20 x 60mm and M24 x 72mm.

What pack sizes are available?
Packs of 2, 5, 10, 25, 50 or 100 in every size.

What size spanner do I need?
Measured across the flats: 8mm for M5, 10mm for M6, 13mm for M8, 17mm for M10, 19mm for M12, 22mm for M14, 24mm for M16, 30mm for M20 and 36mm for M24.

Are extension nuts and connecting nuts the same as coupling nuts?
Yes, these are different names for the same long hex nut: M16 extension nuts are M16 coupling nuts, and an M20 connecting nut is an M20 coupling nut.

Which coupling nut fits my rod?
Match the thread size: an M20 threaded rod needs an M20 coupling nut, an M16 rod an M16 coupling nut, and so on.

What are they made of?
Steel, property class 6, with a bright zinc plated (BZP) finish.