Stainless Steel Long Nuts

Function – when to use a long nut

A long nut (also called coupling nut / extension nut) is a long hex nut used mainly to:

Join two threaded rods/studs end-to-end (extend length).

Allow length adjustment on tie rods, hangers, and bracing members.

Provide extra thread engagement where a normal hex nut is too short.

Typical applications:

Threaded rod assemblies for supports, pipe hangers, cable trays, ducts.

Tie rods / bracing in structures and machinery.

Alignment/adjustment joints where you need to fine-tune length.

Think of a long nut as a connector + adjuster between two threaded pieces, not just a “big nut”.

Environment & corrosion – material selection

For stainless long nuts:

Indoors / general outdoor → A2 (304) long nut

Marine / coastal / chloride / chemical → A4 (316) long nut

Match nut material with the rods/bolts:

A2 long nut with A2 threaded rods/studs

A4 long nut with A4 threaded rods/studs

This avoids galvanic corrosion and gives consistent corrosion resistance across the whole assembly.

Length & thread engagement – the critical choice

The length of the long nut decides how much thread engagement you get on each rod/stud. That directly affects the load capacity.

Common thumb rules:

For normal duty joints:

Aim for at least 1× rod diameter of thread engagement on each side.

For higher loads / safety-critical joints:

Aim for 1.5× rod diameter or follow your design standard.

Examples (simplified rule of thumb):

M10 rod → want at least 10–15 mm full thread engagement per side.

M16 rod → want at least 16–24 mm per side.

Most long nuts are designed with a length of ~2d to 3d (2–3 times the thread diameter) to give adequate engagement for both ends combined.

Key point:

Always ensure the rods are fully engaged inside the long nut – they should not just “catch” a few threads at the ends.

Application type – adjustment vs fixed connection

Adjustment / tensioning joints

Long nuts are often used where you can rotate the nut to lengthen/shorten a tie rod.

Marking the centre of the nut and rod ends can help visually confirm engagement.

Permanent extensions

When used simply to extend two rods, once the correct length is set, you can lock each side with jam nuts if needed for extra security.

If significant tension, compression, or vibration is involved, treat the design like a proper tie-rod system, not just a casual extension.

Long nuts follow the same property classes as standard stainless hex nuts (e.g., A2-70, A4-70).

Their length increases available thread engagement, but basic material strength is the same as the corresponding nut class.

A2-70 Long Nuts

Material: A2 (304) stainless steel

Property class: 70 (compatible with A2-70 rods/bolts).

Suitable for:

General indoor/outdoor structures and supports.

Threaded rod systems in fabrication, HVAC, cable tray, and machinery support.

A4-70 Long Nuts

Material: A4 (316) stainless steel

Property class: 70 (compatible with A4-70 rods/bolts).

Suitable for:

Marine, coastal, chemical, and chloride-rich environments.

Stainless threaded rod systems in plants, offshore structures, water treatment, and food/pharma areas.

Key mechanical points:

For a given size (e.g., M12 A2-70 long nut):

Thread yield and tensile capacity are similar to an M12 A2-70 hex nut.

Additional length allows more thread engagement, which improves:

Resistance to thread stripping

Load distribution between the two rods

The overall joint strength is governed by:

Rod tensile strength

Thread stripping capacity of the nut and rods

Bending or buckling if the rods are used as compression members

Any additional locking elements (jam nuts, etc.)

Long nuts are not a substitute for engineered turnbuckles in highly critical tensioning systems unless specifically designed and rated as such.