Stainless Steel Coupling - Grade 202, 304, 316 - A2, A2-70

A coupling nut, otherwise referred to as a coupler or extension nut, is a fastening device that connects two threaded rods or studs. Essentially, it is an elongated nut with internal threads that enable the joining of two male threads. These nuts are frequently utilized to prolong the length of threaded rods or establish lengthier connections in various applications.

Coupling Technical Specification

Attribute	Details
Shape	Hexagonal (most common), round, knurled
Thread Type	Right-hand (standard), left-hand, or both
Thread Standards	Metric (M6–M24), UNC, UNF, BSW, etc.
Materials	Carbon steel, stainless steel (304/316), brass, alloy steel, aluminum
Finishes	Zinc plated, hot-dip galvanized, plain, black oxide
Lengths	Varies by diameter (usually 1.5–3× the outer diameter of the rod)

Simple and quick extension solution
Available in multiple thread types and finishes
Strong, secure connections
Allows for easy alignment and adjustment
Extending threaded rods in structural assemblies
Joining anchor bolts or threaded studs
Mechanical maintenance and repairs
HVAC and pipe supports
Solar racking systems and construction frameworks

Coupling Nuts – Materials & Grades

Material	Grade	Key Composition / Standards	Properties	Common Applications
Carbon Steel	Grade 2, 5, 8	ASTM A563 / SAE J995	Cost-effective, strong; available with zinc or black oxide coating	Construction, general- purpose fastenings
Stainless Steel	SS 304	18% Cr, 8% Ni – A2-70 (metric)	Good corrosion resistance, non- magnetic, food-safe	Outdoor use, food industry, general stainless applications
Stainless Steel	SS 316	16–18% Cr, 10–14% Ni, 2–3% Mo – A4-70	Superior corrosion resistance, especially in marine/chloride environments	Marine, chemical, coastal infrastructure
Stainless Steel	SS 316L	Low carbon version of SS 316	Better weldability, reduced risk of carbide precipitation	Welded joints, medical, pharmaceutical industries
Brass	CDA 360 or equivalent	Copper-zinc alloy	Good corrosion resistance, non- sparking, decorative look	Plumbing, electrical, decorative hardware
Alloy Steel	ASTM A194 Grade 7/12	Chromium-molybdenum steel	High strength, used in high- pressure/high-temp conditions	Heavy machinery, power plants, pressure vessels
Aluminum	6061-T6	Magnesium & silicon alloy	Lightweight, corrosion-resistant, non-magnetic	Aerospace, electronics, light structures
Hot-Dip Galvanized Steel	ASTM A563	Low carbon steel + zinc coating	Excellent for outdoor & structural use, highly corrosion-resistant	Structural joints, pole mounts, outdoor applications

Mechanical Properties of Coupling Nut Materials

Material / Grade	Tensile Strength (MPa)	Yield Strength (MPa)	Hardness (HB / HRC)	Notes
Carbon Steel – Grade 2	420	250	~120 HB	Economical, low strength; general use
Carbon Steel – Grade 5	830	600	~200 HB / 22 HRC	Medium strength; automotive, machinery
Carbon Steel – Grade 8	1040	860	~250 HB / 28 HRC	High strength; heavy-duty, structural
Stainless Steel – SS 304	515	205	~150 HB	Corrosion-resistant, non-magnetic, general-purpose
Stainless Steel – SS 316	520	215	~150 HB	Better corrosion resistance, especially in marine/chemical environments
Stainless Steel – SS 316L	485	170	~140 HB	Low carbon version; better for welding
Brass (C36000)	350	100	~80 HB	Soft, non-sparking, corrosion-resistant
Aluminum 6061-T6	310	275	~95 HB	Lightweight, moderate strength
Alloy Steel – Grade 12	1200	1000	~300 HB / 32–35 HRC	Very high strength; high-temp and pressure applications

A coupling nut (also called an extension nut) is a long hexagonal or cylindrical nut used to connect two male threaded fasteners, typically threaded rods or studs. It allows for the extension of threaded components in structural, mechanical, and plumbing applications.

Material

Stainless Steel

Composition

18% Cr, 8% Ni – A2-70 (metric)

Yield Strength (MPa)

1000 Max

Hardness (HB / HRC)

~300 HB / 32–35 HRC

Joining Threaded Rods

A coupling nut serves to join two threaded rods, extending their length.

Extending Connections

These tools have the capability to increase the length of a bolt or stud, making it possible to create longer assemblies or connections.

Joining Components

In addition, these nuts are suitable for connecting a variety of internally threaded parts, including pipes.

Hexagonal Shape

Coupling nuts typically feature a hexagonal design on their exterior, enabling easy use of a wrench or socket for tightening and loosening.

Internal Threads

The internal threads of these connectors perfectly match the external threads of the components they are joining together.

Material and Finish

These materials come in a variety of options such as steel, stainless steel, zinc plating, and galvanizing.

Reducing Coupling Nuts

Certain coupling nuts enable the joining of rods with varying diameters, resulting in a decrease in thread size.

Left-Handed Thread

Left-handed threaded coupling nuts may be utilized in certain applications.

Sight Hole

Certain coupling nuts feature a sight hole that enables the inspection of thread engagement.

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