Weld screws are of two types: projection weld and spot weld. Both involve resistance welding principles where the welded joint is achieved by electrical resistance flow through the joint held under electrode pressure. Weld screws are ideal for providing quick, strong and permanent bonds to metal surfaces.
Projection Weld Screws
The two surfaces of the welded joint are held together by pressure from the welding electrodes. Electrical current passing through the electrodes causes the projecting metal of the screw head to melt and fuse with the adjacent metal surface thereby forming the welded joint.
The projections on weld screws are located either under or on top of the head of the screw each being preferable for specific applications. Different types of projections are also available:
- Button type
- Cone type
- Spherical type
The different projection types directly affects the heat generated during the welding process and effects the properties of the final welded joint. This of course influences the type used for different surfaces and materials. For instance, button type projections are ideal for joining thin flat metal sheets; cone type projections are used on thicker materials; and spherical type projections are ideal for thicker metal plates.
Advantages of Projection welding:
- Numerous welded joints can be performed simultaneously
- Surface conditions and finishes (rust, coating, oil etc.) do not affect this welding process
- Electrode life is longer than spot welding
- Improved temperature control for different material composition and thickness
Spot Weld Screws
Spot welding involves placing the spot weld screw and the surface on to which it is to be welded between two welding electrodes. An electric current is passed through the electrode tips producing sufficient heat to fuse the metals together forming the welded joint. In spot welding, the heat generated depends on the size and shape of the electrode tips rather than on the size, shape and the number of projections used.
The size and shape of the welding electrode tip directly influences the size of the weld, and therefore also determines the final strength of the welded joint. For this reason, welding electrode tip diameters must be changed for each thickness of metal to be welded.
Advantages of spot welding
- Free of fumes and splatter
- Easy to use operating equipment
- Simple and Quick process
- Low cost
Another potentially important advantage of spot welding is it can be used to weld fasteners to assemblies also being spot welded. This minimizes setup time and costs and maximizes the use of the spot welding equipment.
Weld Screws In Stock at Aspen Fasteners:
Weld Screws – Projections Over Head
- Three projections on top of the head 120° apart
- For welding to the surface of a steel plate
- Eliminates the need for holes in the surface material
- No screw head protrudes through the surface
- The exterior surface remains virtually unmarred
- Ideal for applications where product appearance or potential leakage is a consideration
- Ideal in blind locations as the screw can be pre-welded in place.
Weld Screws – Projections Under Head
- Three projections under the head 120° apart
- Allows for flush mounting
- For through hole applications
- The through hole allows self alligning
- Eliminates the need for fixturing.
Weld Screws – Spot Weld Type
- Has a flat spade perpendicular to the thread
- Ideal for confined areas such as narrow channels, corners and in applications requiring thread offset from component surfaces
- This screw is easy to position and produces a strong weld
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Aspen Fasteners stocks full lines of steel weld screws screws in addition to most other screws, nuts, bolts and washers. Available for same day shipping from distribution centers across the USA. And remember, it’s always free shipping. Expedited next day delivery is also available for those rush requirements.
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