The Simpson Strong-Drive SDHR Combo-Head Screw in 0.470 in. diameter by 6-1/4 in. length is a heavy-duty structural fastener engineered for cross-laminated timber construction, mass timber construction, and general interior applications. Designed by Simpson to pull structural members firmly together, this partially-threaded screw delivers excellent connection strength and reliable performance in demanding timber framing and interior structural assemblies. The blue-zinc coating and knurled shaft make it a dependable choice for professionals who need consistent, low-torque driving and strong clamping force in structural wood connections.

Key Features

• Combination Head (0.669 in. diameter) - accepts either a T40 6-lobe or 17-mm hex-head driver bit, giving installers the flexibility to use whatever driver is on hand and reducing downtime on the job site.
• Partial Threading with 4-3/8 in. thread length - the partially-threaded design clamps structural members tightly together rather than threading through both, maximizing connection strength in mass timber and cross-laminated timber assemblies.
• Type-17 Point - bores into dense timber quickly for fast starts and significantly reduced driving torque, making it easier to drive long structural fasteners without pre-drilling in many applications.
• Knurled shaft (0.315 in. shank diameter) - the robust knurled section resists rotation and improves grip within the wood substrate, contributing to a more secure and stable structural connection.
• Blue-zinc interior-grade coating - provides a corrosion-resistant finish suited for interior structural applications, protecting the fastener during the life of the assembly.
• 0.470 in. outer diameter - the larger-diameter shank carries greater shear and withdrawal loads compared to standard wood screws, meeting the demands of structural timber connections.
• T40 6-lobe driver bit included - eliminates the need to source a separate bit, so you can begin driving immediately upon opening the package.

Why This Product

• Built for mass timber and CLT construction - the SDHR Combo-Head is specifically engineered for cross-laminated timber and mass timber applications where structural integrity and strong member-to-member clamping are critical requirements, not an afterthought.
• Two driver options in one head - the combination head design accommodates both a T40 6-lobe and a 17-mm hex driver bit, eliminating the frustration of mismatched bits and keeping work moving when driver options vary across a crew.
• Fast, low-torque installation without sacrificing strength - the Type-17 point and knurled shaft work together to reduce driving effort in dense structural timber, meaning less fatigue for the installer and faster completion of structural connections.
• Structural fastener with a T40 bit included - because the matching driver bit ships with the product, installers have everything needed to begin structural driving immediately, reducing the risk of job-site delays caused by missing accessories.

Specifications

• Brand: Simpson Strong-Tie
• Coating: Blue-Zinc Coated
• Length: 6-1/4 in.
• Head Type: Combination
• Head Diameter: 0.669 in.
• Shank Diameter: 0.315 in.
• Outer Diameter: 0.470 in.
• Thread Length: 4-3/8 in.
• Drive Type: T40 6-Lobe or Hex-Head
• Point Type: Type-17 Point
• Country of Origin: Taiwan

Available Pack Options

• SDHR31614-R25: 25 Pk - includes T40, 6-lobe driver bit (replacement bit: BIT40T-134-R2)
• SDHR31614: 100 Pk - includes T40, 6-lobe driver bit (replacement bit: BIT40T-134-R2)

Install With

• 6-lobe T40 or 17-mm hex-head driver bit

Frequently Asked Questions

What makes the "combination" head different from a standard screw head?

The combination head on the SDHR Combo-Head screw is engineered to accept either a T40 6-lobe driver bit or a 17-mm hex-head driver bit. This dual-drive compatibility gives installers the freedom to use whichever bit is available, reducing delays when working across different tool setups or crew configurations.

Is this screw suitable for cross-laminated timber and mass timber construction?

Yes. The SDHR Combo-Head screw is specifically designed for cross-laminated timber construction, mass timber construction, and general interior structural applications. Its partially-threaded design pulls structural members firmly together, and the 0.470 in. outer diameter provides the load-carrying capacity needed in these demanding assemblies.

Does the Type-17 point require pre-drilling in structural timber?

The Type-17 point is engineered for fast starts and low-torque driving, allowing the fastener to bore into dense structural timber efficiently. This point style is designed to reduce the need for pre-drilling in many applications while still achieving clean, controlled entry into the wood substrate.

What is the thread length versus the total length of this screw?

This screw has a total length of 6-1/4 in. with a thread length of 4-3/8 in. The partial-thread design is intentional - the unthreaded shank section allows the head-side member to be drawn tight against the threaded member, maximizing clamping force and connection strength in structural timber applications.

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