Stainless Steel Square Weld Nuts

Function – when to use a square weld nut

Use a square weld nut when you want a permanent threaded point on a plate or sheet and:

You only have access from one side (e.g., box sections, hollow sections, closed frames)

You want to save assembly time vs loose nut + bolt

The nut should never rotate or fall off once installed

You want a clean, flush side on the opposite face (no loose nut visible)

They’re ideal for: brackets, frames, enclosures, cabinets, automotive/railway structures, fabricated machinery parts, etc.

Environment & corrosion

Indoors / general outdoor → A2 (304) square weld nut

Marine / coastal / chloride / chemical → A4 (316) square weld nut

A2 for general fabrication, machinery, frames, cabinets, indoor and standard outdoor environments.

A4 wherever there is salt, sea air, chemicals, pools, cooling towers, or strong cleaners.

Always try to match material with the mating bolt:

A2 weld nut with A2 bolts

A4 weld nut with A4 bolts

Weld style & base material thickness

Square weld nuts are available as:

Projection weld nuts (with small weld projections)

Designed for resistance/spot welding to thin sheet

Projections collapse during welding to create consistent weld nuggets

Ideal for automated production and repetitive assemblies

Plain-face weld nuts (flat base)

Can be attached with fillet welds around the nut

Better for thicker plates or where projection welding is not available

Selection thumb rule:

Thin sheet / automated line → Projection weld nut

Thick plate / manual welding → Plain-face weld nut with fillet welds

Thread size, load & engagement

When choosing the size:

Select thread diameter (M6, M8, M10, etc.) based on the clamping load and bolt size required.

Ensure proper thread engagement:

Bolt must engage enough threads inside the weld nut (typically at least 1× bolt diameter in steel designs, or as per your design standard).

Check base plate thickness + weld quality – the joint strength is the combination of:

Bolt strength

Nut thread strength

Weld strength to the plate

Hole & fit (for pilot-type weld nuts)

Some square weld nuts have a pilot / boss to fit into a punched hole:

Helps with self-location and alignment during welding

Improves strength and positioning

Reduces risk of weld spatter entering threads

Make sure your hole size & tolerance match the nut’s pilot dimension if you’re using this style.

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

The nut’s thread strength is similar, but the joint capacity also depends heavily on weld quality and base plate.

A2-70 Square weld nuts

Material: A2 (304) stainless steel

Property class: 70 (matched to A2-70 bolts)

Suitable for:

General indoor/outdoor fabrication

Machinery frames, cabinets, brackets, equipment enclosures

Places where you want a permanent stainless thread in mild environments

A4-70 Square weld nuts

Material: A4 (316) stainless steel

Property class: 70 (matched to A4-70 bolts)

Suitable for:

Marine, coastal, chemical, chloride-rich environments

Structural stainless frames, handrails, plant equipment, exposed outdoor assemblies

Situations where both corrosion resistance and permanent attachment are important

Remember:

The bolt + nut property class gives you the threaded joint strength,

But the weld itself must be sized and executed correctly to carry the load.

Poor welding can reduce the effective joint strength regardless of nut class.