Weld nuts are part of the category of nuts known as captive nuts, labeled as such because, once successfully installed, they become an integrated part of the assembly. 

Weld nuts are well suited for various applications, including fastening when only one side of the component material is accessible. But how do they work and what are they useful for? 

In this article, we’ll cover the following: 

What Is a Weld Nut? 

A weld nut is a type of fastener designed to weld to another component in an assembly. Weld nuts can replace sheet metal screws in thin sheet metal applications. Once welded, they form a powerful bond. 

How Do Weld Nuts Work? 

There are two methods of installing weld nuts in metalwork: projection welding or capacitive discharge welding. 

Weld nuts are manufactured with pins, or ashlars, in specific areas. These pins will merge after an electrical current is applied, conducted by electrodes positioned at either side of the component. This is the case in both projection welding and capacitive discharge welding.

Types of Weld Nuts and Their Uses 

There are several types of weld nuts available, each suited to specific applications, including: 

Tab Spot Weld Nuts 

Available in various thread sizes and materials, tab spot weld nuts are well-suited for applications where space is limited. Tab spot weld nuts are manufactured with a tab that can accommodate electrodes of various sizes, and their design makes them easy to spot weld on flat surfaces. 

Tab Projection Weld Nuts 

Ideal for use in heavy gauge sheet metals or on curved surfaces, tab projection weld nuts have a single projection to produce a penetrating and robust weld. 

Hex 3 Projection Weld Nuts 

Hex 3 projection weld nuts are well suited to industrial and heavy-duty applications as they can withstand greater torque than other non-welded nuts. This type of weld nut has greater resistance to moving and twisting for high-torque applications. 

Square Projection Weld Nuts 

Most commonly used in automotive applications and the manufacturing of farm equipment, square projection weld nuts have four uniform projections, which ensure strong and reliable welds are formed with the correct seating. 

This type of nut is available in various thread sizes and dimensions and can be configured as either piloted or unpiloted. 

Round Base Weld Nuts 

Round base weld nuts are available in low-carbon steel and stainless steel. They're well suited for applications where restricted space and orientation are limiting factors, as they can be installed with automatic feeding equipment.  

Flange Weld Nuts 

This category covers several types of weld nuts, including stamped flange weld nuts, through-the-hole flange weld nuts and on-the-material flange weld nuts. 

Generally speaking, flange weld nuts can be used to create strong joints. Some types, like the through-the-hole flange weld nut, are perfect for applications that require a heavy weld, whereas others, such as ring projection or square body flange weld nuts, are better for welding thin-gauge metal sheets. 

Alternatives to Weld Nuts: Blind Rivet Nuts 

As an alternative to weld nuts, blind rivet nuts offer a quick and simple installation. While some equipment is needed to install this type of nut, it’s generally less expensive than that required to install a weld nut. 

Unlike weld nuts, blind rivet nuts can be fixed into blind holes, making them suitable for applications where space is limited, as you won’t need access to both sides of the material to install them. 

They’re also available with different plating options, making them less likely to corrode. (Weld nuts aren’t pre-coated for protection against corrosion — paint or plating will need to be applied after the welding process is complete). 

Alternatives to Weld Nuts: Self-Clinching Fasteners 

Self-clinching nuts are available with several different types of plating and can even be heat treated to provide more strength in a joint. 

Usually used in softer sheet metal, the self-clinching fastener provides the strongest threads and with various strength options available, is well suited for a host of sheet metal applications. 

Which Is the Best Fastening Method for Me?

While several approaches can be taken to joining sheet metal, the question of which fastening method is the best depends on numerous factors. 

Ultimately, the best fastening method for you will depend on the materials you’re joining together, the access and space you have for installation, the strength of the bond required, the equipment at your disposal and the budget you’re working towards, among various other factors. 

For a comprehensive overview of the benefits of welding when compared with other viable alternatives, read our article. 

Make the Switch to PEM® Self-Clinching Fastener Technology

In our article, assess the benefits of self-clinching fastener technology vs. traditional welding methods and discover why you should make the switch today. 

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