Everything You Need to Know About Bimetal Screws: A Practical Buyer’s Guide

Why Not Just Use Stainless or Carbon Steel?

Each standard material covers only part of the job.

• Stainless steel (304/316)
  • Great against rust
  • Soft when drilling thicker steel
  • Often needs pre-drilling
• Carbon steel
  • Hard, drills fast
  • Rusts quickly outdoors unless coated
  • Coatings can get damaged during installation

Bimetal screws borrow the best from both. They drill like carbon steel and resist corrosion like stainless. That’s why they show up wherever you need both.

What Materials Are Used in Bimetal Screws (304 vs 316)?

The choice comes down to the stainless part.

• 304 stainless (A2)
  • Good for general outdoor use
  • Suitable for moderate humidity environments
• 316 stainless (A4)
  • Better resistance to salt and chemicals
  • Preferred for coastal, marine, or industrial environments

The drill tip is hardened carbon steel, designed to stay sharp when penetrating metal sheets or structural steel.

Pick 304 or 316 based on the environment, not just the application.

Can Bimetal Screws Be Used in Steel and Aluminum Structures?

Yes. They are commonly used in both.

Typical applications include:

• Steel structures and metal roofing
• Aluminum profiles and framing systems
• Solar mounting systems (PV installations)

The main advantage is direct drilling into metal without pre-drilling. This speeds up installation and reduces labor time.

Drilling capacity varies by design, but for light to medium steel sections commonly found in construction and solar projects, they perform reliably.

How Do Bimetal Screws Perform in Corrosive Environments?

Outdoors—especially near salt water or in high humidity—corrosion is a key concern.

Bimetal screws outperform coated carbon steel fasteners because:

• The exposed surface is stainless steel, not a coating
• There is no thin protective layer to scratch or wear through
• Corrosion resistance is built into the material itself

In environments rated C3 to C5-M (ISO 12944), the difference becomes more noticeable over time.

For long-life projects such as solar farms or infrastructure, this leads to fewer maintenance interventions.

How Can You Identify a High-Quality Bimetal Screw?

Not all bimetal screws are the same. Manufacturing quality matters.

Key points to check:

• Welding quality
  The joint between the carbon tip and stainless body should be smooth and consistent. Poor welding can lead to failure during installation.
• Concentricity
  The screw should rotate without wobble. Misalignment affects drilling efficiency and torque performance.
• Material traceability
  Reliable suppliers provide batch-level documentation (such as MTRs).
• Surface condition
  Threads should be clean, without visible defects that could affect installation.

These factors are not always visible in photos, which is why supplier consistency matters.

Are Bimetal Screws More Expensive?

Yes, the unit price is higher than coated carbon steel screws.

However, fasteners represent only a small portion of total project cost. The more important factor is long-term expense.

Bimetal screws help reduce:

• Installation time (no pre-drilling required)
• Maintenance frequency in outdoor environments
• Risk of early replacement

For projects designed to last 15–25 years, these savings often outweigh the initial cost difference.

Where Are Bimetal Screws Most Commonly Used?

Bimetal screws are used wherever both drilling performance and corrosion resistance are required.

Typical industries include:

• Solar mounting systems
• Metal roofing and cladding
• Steel structure construction
• Coastal or high-humidity projects

In these environments, standard fasteners tend to fail earlier, making bimetal screws a more reliable long-term option.

Overall

Bimetal screws are not new, but their use is increasing as projects demand longer service life and lower maintenance. They solve a practical problem: how to install quickly while maintaining durability in outdoor conditions.

For buyers, the decision is not about choosing a “better screw,” but about matching the fastener to real working environments.

Fasto supplies bimetal screw solutions for construction and photovoltaic applications, with controlled production and consistent quality. The focus is on stable performance across long-term projects.

We supply high-quality, customizable fasteners to meet a wide range of project needs.

📧 Contact Us for more information.
🌐 You can also explore our Full Product Catalog for detailed specifications.