Simpson #12 x 3" Self-Drilling Hex-Washer Head Screw in 305 Stainless Steel is a purpose-built fastener designed for securing aluminum and fiberglass materials where a reliable, corrosion-resistant connection is essential. The #3 drill point eliminates the need for pre-drilling, saving installation time and reducing labor on the job site. With its indented hex-washer head and tapping screw thread profile, this screw delivers consistent clamping force and a secure hold in non-ferrous substrates - making it a trusted choice for contractors, fabricators, and builders working with aluminum panels, fiberglass sheeting, and similar materials.

Key Features

• 305 Stainless Steel construction - provides strong resistance to corrosion and oxidation, keeping fasteners looking and performing well even in demanding outdoor or moisture-exposed environments
• #3 drill point - self-drilling tip cuts through aluminum and fiberglass without pilot holes, speeding up installation and reducing the need for additional tools
• Indented hex-washer head with 5/16 in. drive - distributes clamping load over a wider surface area for a secure, stable connection that resists pull-through in soft materials
• Tapping screw thread with 14 TPI - thread-forming design creates its own mating thread in the material, resulting in a tight, vibration-resistant fit without the need for a pre-tapped hole
• 3 in. length with #12 screw size - provides sufficient shank depth for fastening through layered or thicker aluminum and fiberglass assemblies

Why This Product

• Engineered specifically for aluminum and fiberglass fastening - the #3 drill point and tapping thread are optimized for these non-ferrous materials, reducing the risk of cracking or splitting that can occur with improper fasteners
• The 305 stainless steel alloy makes this screw well-suited for exterior applications and wet environments where carbon steel fasteners would corrode and stain the surrounding material
• The self-drilling tip eliminates a separate drilling step, which translates directly to faster assembly times when working on large aluminum panel installations or fiberglass projects
• The hex-washer head style allows for easy driving with a standard 5/16 in. hex socket or nut driver, providing good torque transfer and reduced cam-out compared to slotted or Phillips-head alternatives

Specifications

• Brand: Simpson Strong-Tie
• Screw Size: #12
• Length: 3 in.
• Material/Coating: Type 305 Stainless Steel
• Head Type: Hex Washer Head (Indented)
• Drive Type: 5/16 in. Hex
• Thread Type: Tapping Threads
• TPI: 14
• Point Type: #3 Drill Point
• Country of Origin: Taiwan

Available Pack Options

• S12300HDUC: 100 Pk
• S12300HDUM: 1000 Pk

Approved Applications

• Fastening aluminum panels and assemblies
• Securing fiberglass sheets and components
• Non-ferrous substrate connections requiring corrosion-resistant hardware
• Exterior and moisture-exposed installations where stainless steel performance is required

Frequently Asked Questions

Can this screw be used to fasten into steel?

No. This screw is designed for aluminum and fiberglass fastening only and is not recommended for use in steel applications. Using it in steel could result in inadequate holding strength or premature fastener failure.

Do I need to pre-drill a pilot hole before installing this screw?

No pilot hole is required. The #3 drill point is a self-drilling tip that bores through aluminum and fiberglass as the screw is driven, eliminating the pre-drilling step and simplifying installation.

What tool do I need to drive this screw?

This screw uses a 5/16 in. hex drive. A standard hex socket, nut driver bit, or hex-tip power driver in 5/16 in. size will seat properly and deliver the torque needed for secure installation.

Why is 305 stainless steel a good choice for outdoor or exposed fastening applications?

305 stainless steel offers corrosion resistance that helps the fastener maintain its integrity in environments exposed to moisture, humidity, or the elements. This makes it a practical choice when fastening aluminum or fiberglass in exterior settings where rust or staining would be a concern with standard steel hardware.

Note: Product dimensions and/or thread length may differ from picture. Please see the item description above for specifications.