What Is A Bi-Metal Screw?

Understanding Bi-Metal Screws: Durable Fastening Solutions for Harsh Environments

In construction and metalworking industries, choosing the right fastener can make a big difference in terms of durability, safety, and cost-effectiveness. One high-performance solution is the bi-metal screw, which is engineered to combine the strength of carbon steel with the corrosion resistance of stainless steel. These bi-metal self-drilling screws are ideal for demanding environments and have become an essential component in modern building and assembly applications.

What is a Bi-Metal Screw?

A bi-metal screw (also spelled bimetal screw) is a specialized type of self-drilling screw composed of two different metals:

• The head and body are made of stainless steel (usually A2 or A4 grade) to ensure corrosion resistance.

• The drill point or drill tip is made of hardened carbon steel or alloy steel to allow efficient drilling into hard materials like steel or aluminum.

The bi-metal construction provides both the longevity of stainless steel and the drilling capability of hardened steel—making these screws ideal for metal-to-metal fastening.

Key Features of Bi-Metal Screws

• Corrosion Resistance: The stainless steel body resists rust and corrosion, making bi-metal screws perfect for outdoor applications, marine environments, or industrial use.

• Self-Drilling Tip: Eliminates the need for pre-drilling, reducing installation time and labor costs.

• High Strength: The hardened tip can drill through thick steel, aluminum panels, or even structural steel.

• Thermal Expansion Compatibility: Often used in projects involving dissimilar metals, bi-metal screws help minimize issues caused by thermal expansion and galvanic corrosion.

Common Applications

Bi-metal screws are used across a variety of industries, including:

• Roofing and Cladding Systems

• HVAC Installation

• Metal Framing and Structural Steelwork

• Solar Panel Mounting Systems

• Shipbuilding and Marine Structures

• Automotive and Railway Maintenance

Types of Bi-Metal Screws

There are different types of bi-metal fasteners designed to meet specific needs:

1. Bi-Metal Self-Drilling Screws
   These screws combine drilling, tapping, and fastening in a single operation.

2. Bi-Metal Roofing Screws
   Often equipped with EPDM washers for watertight sealing on metal roofing panels.

3. Hex Head Bi-Metal Screws
   Provide greater torque and grip, ideal for heavy-duty fastening.

4. Bi-Metal Wood-to-Metal Screws
   Designed to fasten wooden elements to steel substrates securely.

Benefits of Using Bi-Metal Screws

• Time-Saving Installation: No pilot hole needed.

• Reduced Equipment Wear: Eliminates the need for separate drill bits or taps.

• Lower Maintenance: Excellent resistance to weathering and chemical exposure.

• Reliable Performance: Secure and vibration-resistant fastening, even in high-load or high-wind conditions.

Choosing the Right Bi-Metal Screw

When selecting a bi-metal screw, consider the following:

• Screw Size and Thread Type – Match the material thickness and load requirements.

• Point Style (Drill Tip Number) – Determines how thick a material it can drill through.

• Head Style (Hex, Pan, Countersunk) – Depends on whether the fastener will be visible or recessed.

• Coatings and Washers – For additional sealing and insulation in outdoor or corrosive environments.

Conclusion

Bi-metal screws offer a superior fastening solution that merges the corrosion resistance of stainless steel screws with the drilling efficiency of hardened tips. Whether you're working in construction, marine engineering, or metal fabrication, these durable fasteners provide long-term reliability and ease of installation. With their versatility and proven performance in harsh conditions, bi-metal self-drilling screws are a smart investment for any serious project.