Simpson #12 x 2-1/2" Self-Drilling Hex-Washer Head Screw in 316 Stainless Steel is a heavy-duty fastener engineered for demanding applications where corrosion resistance is non-negotiable. Built by Simpson from Type 316 stainless steel - the grade widely recognized for superior resistance to saltwater, moisture, and harsh chemical environments - this screw drives without a pre-drilled pilot hole, saving time and labor on the job. The hex-washer head accepts a 5/16 in. hex driver for secure, high-torque installation, making it a reliable choice for marine, coastal, and outdoor fastening work in aluminum and fiberglass assemblies.

Key Features

• Type 316 Stainless Steel construction - delivers outstanding corrosion resistance in saltwater, coastal, and chemically aggressive environments where lesser grades would degrade and fail
• Self-drilling #3 drill point - eliminates the need for pre-drilling pilot holes, reducing installation steps and speeding up the fastening process
• Indented hex-washer head with 5/16 in. hex drive - provides a broad bearing surface for improved load distribution while enabling high-torque driving without cam-out
• Tapping screw thread at 14 TPI - cuts its own mating threads upon entry, creating a firm, vibration-resistant hold in the base material
• #12 diameter x 2-1/2 in. length - a robust size suited to structural and semi-structural connections in aluminum and fiberglass assemblies where holding power matters
• Sold individually - allows you to purchase the exact quantity needed for your project without waste

Why This Product

• Type 316 stainless steel is specifically chosen for environments that would corrode standard zinc or 304-grade fasteners - making this screw the right call for marine hardware, boat components, coastal decking, and similar wet or salt-spray applications
• The self-drilling tip means you can fasten aluminum panels or fiberglass assemblies in a single operation, without stopping to switch bits or pre-drill each hole - a meaningful time saver on repetitive installation tasks
• The hex-washer head design combines the clamping area of a washer face with the grip of a hex drive, reducing the risk of stripping and delivering a clean, finished appearance on exposed fastener locations
• Specified for aluminum and fiberglass fastening - this screw is purpose-matched to these materials, avoiding galvanic compatibility issues that can arise when the wrong fastener material is paired with non-ferrous substrates

Specifications

• Brand: Simpson Strong-Tie
• Coating/Material: Type 316 Stainless Steel
• Screw Size: #12
• Length: 2-1/2 in.
• Drive Type: 5/16 in. Hex
• Head Type: Hex Washer Head (Indented)
• Thread Type: Tapping Threads
• TPI: 14
• Point Type: #3 Drill Point
• Country of Origin: Taiwan

Available Pack Options

• T12250HDUC: 100 Pk
• T12250HDUM: 1000 Pk

Approved Applications

• Fastening aluminum components and panels
• Fastening fiberglass assemblies and panels
• Marine and coastal hardware installations
• Outdoor structures exposed to moisture, salt air, or chemical environments
• Note: Not intended for fastening steel.

Frequently Asked Questions

Can this screw be used to fasten steel?

No. This screw is approved for fastening aluminum and fiberglass only. It is not rated or recommended for use with steel, and using it in steel applications could result in inadequate holding strength or material compatibility issues.

What driver size is required to install this screw?

This screw uses a 5/16 in. hex drive. A hex-head driver bit or socket of that size is needed to install it. The indented hex-washer head is designed to accept standard hex-driver tooling for a firm, torque-stable connection.

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

No. This is a self-drilling fastener with a #3 drill point that bores its own hole as it drives. No pilot hole is required when fastening into aluminum or fiberglass, simplifying the installation process.

Why is 316 stainless steel specified instead of a standard stainless grade?

Type 316 stainless steel contains molybdenum, which significantly improves resistance to chloride corrosion - including saltwater and salt spray. This makes it the preferred material for marine, coastal, and chemically exposed environments where Type 304 stainless or zinc-plated fasteners would be prone to premature corrosion and failure.

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