Simpson #12 x 3" Self-Drilling Hex-Washer Head Screw in 316 Stainless Steel is a precision-engineered fastener built for demanding applications where corrosion resistance is non-negotiable. Featuring a #3 drill point that eliminates the need for pre-drilling, this screw drives cleanly into aluminum and fiberglass materials, creating a secure, lasting connection. The indented hex-washer head provides broad bearing surface and a reliable 5/16 in. hex drive engagement, making it a dependable choice for marine, coastal, and chemical-exposure environments where standard fasteners fail prematurely.

Key Features

• 316 Stainless Steel construction - delivers superior resistance to saltwater, chlorides, and harsh chemicals, making this screw ideal for coastal, marine, and outdoor installations where corrosion is a constant concern.
• #3 drill point - self-drills through aluminum and fiberglass without requiring a pilot hole, saving installation time and reducing the number of tools needed on the job.
• Indented hex-washer head - the integrated washer spreads clamping load over a wider area, reducing the risk of pull-through and providing a more secure hold in softer substrates like fiberglass panels.
• 5/16 in. hex drive - compatible with standard hex drivers and impact tools, allowing for fast, efficient installation with consistent torque application.
• Tapping screw thread at 14 TPI - cuts its own mating thread during installation, eliminating the need for a separate tapping step and ensuring a tight, vibration-resistant fit.
• 3 in. length with #12 diameter - provides deep thread engagement and strong pull-out resistance in aluminum framing and fiberglass panel assemblies.

Why This Product

• 316 stainless steel is the go-to material for fasteners exposed to saltwater, humidity, and chemical environments - this screw holds up where zinc-plated or even 304 stainless fasteners can corrode and fail over time.
• The self-drilling tip eliminates the pre-drill step entirely when working with aluminum and fiberglass, cutting labor time and reducing the chance of misaligned pilot holes during installation.
• The hex-washer head design combines drive engagement and load distribution in a single head style, reducing the likelihood of cam-out and giving you a flush, professional finish on exposed fastening points.
• From Simpson, a brand recognized in the structural fastener industry, this screw is built to consistent dimensional tolerances - giving installers confidence in repeatable performance across large-volume applications.

Specifications

• Brand: Simpson Strong-Tie
• Screw Size: #12
• Length: 3 in.
• Material/Coating: 316 Stainless Steel
• Head Type: Indented Hex Washer Head
• Drive Type: 5/16 in. Hex
• Thread Type: Tapping Threads
• TPI: 14
• Point Type: #3 Drill Point
• Country of Origin: Taiwan

Available Pack Options

• T12300HDUC: 100 Pk
• T12300HDUM: 1000 Pk

Approved Applications

• Fastening aluminum panels, frames, and extrusions
• Securing fiberglass panels and composite assemblies
• Marine and coastal construction where corrosion resistance is critical
• Outdoor structural and architectural applications exposed to moisture and chemicals

Frequently Asked Questions

Can this screw be used to fasten into steel?

No. This self-drilling hex-washer head screw is specifically designed for fastening aluminum and fiberglass only. It is not approved or recommended for use in steel applications.

Does this screw require a pilot hole before installation?

No pilot hole is required. The #3 drill point allows this screw to self-drill through aluminum and fiberglass, driving directly into the material and cutting its own thread as it goes.

Why choose 316 stainless steel over other stainless grades for this type of fastener?

316 stainless steel contains molybdenum, which significantly improves resistance to chlorides, saltwater, and industrial chemicals compared to 304 stainless steel. This makes it especially well-suited for marine environments, coastal construction, and applications where chemical exposure is a concern.

What tool is needed to drive this screw?

This screw uses a 5/16 in. hex drive, which is compatible with standard hex nut drivers, socket drivers, and most corded or cordless impact drivers equipped with a matching hex bit or socket attachment.

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