The Simpson Strong-Drive SDCP Timber-CP Screw with T40 6-Lobe drive, 0.390 x 7-7/8 inch, Yellow-Zinc Coated is a structural fastener engineered for cross-laminated timber construction, mass timber construction, and general interior applications. Designed by Simpson to pull structural members together with exceptional holding power, this partially-threaded screw delivers the precision and reliability that demanding timber framing connections require. The yellow-zinc coating provides a clean, finished appearance suited to interior structural work, while the flat head design with underhead nibs ensures smooth, professional countersinking every time.

Key Features

• Yellow-Zinc Coating - provides a corrosion-resistant finish appropriate for interior structural applications, keeping connections protected and visually consistent
• 7-7/8 inch length with 3-1/8 inch thread length - the long shank combined with partial threading pulls structural members tightly together, making it ideal for thick mass timber assemblies
• 0.390 inch nominal diameter (0.275 inch shank diameter) - heavy-duty shank size delivers high shear and withdrawal strength in timber-to-timber connections
• T40 6-Lobe drive - the torx-style interface reduces bit cam-out during installation, giving installers better control and faster, more reliable driving in structural timber
• Flat head with underhead nibs (0.7 inch head diameter) - the wide flat head and nibs allow for clean, flush countersinking into timber surfaces without the need for pre-drilling a recess
• Type-17 point - the self-drilling tip bores into wood without splitting, reducing the need for pre-drilling and speeding up installation in mass timber panels and beams
• Partially threaded design - the unthreaded shank zone acts as a clamping mechanism, drawing mating members firmly together for tight, gap-free joints

Why This Product

• Purpose-built for cross-laminated timber (CLT) and mass timber construction, this screw addresses the specific demands of modern engineered wood assemblies - where standard fasteners lack the shank length and holding capacity required
• The T40 6-Lobe drive combined with the Type-17 self-drilling point means fewer installation steps - no pre-drilling in most applications - reducing labor time and the chance of misaligned pilot holes in structural connections
• The large flat head with underhead nibs countersinks cleanly and stays flush with the timber surface, which matters in panel-to-beam and surface spline applications where a proud fastener head would interfere with fit-up
• Partially threaded geometry pulls mating wood members together under load as the screw is driven, producing tight, structurally sound joints in lap connections, ledger connections, and wall-to-floor assemblies without needing additional clamping

Specifications

• Brand: Simpson Strong-Tie
• Finish: Yellow-Zinc Coated
• Length: 7-7/8 in.
• Head Diameter: 0.7 in.
• Shank Diameter: 0.275 in.
• Drive Type: T40 6-Lobe
• Head Type: Flat Head with Nibs
• Thread Length: 3-1/8 in.
• Point Type: Type-17 Point
• Measurement Unit: Pack

Available Pack Options

• SDCP27778-R30: 30 Pk
• SDCP27778: 250 Pk

Approved Applications

• Wall to wall connections
• Floor to floor connections
• Wall to floor connections
• Panel to beam connections
• Panel to wall connections
• Surface splines
• Lap joints
• Ledger connections
• General timber framing
• Cross-laminated timber (CLT) construction
• Mass timber construction
• General interior structural applications

Frequently Asked Questions

Is this screw designed for exterior or interior use?

The Strong-Drive SDCP Timber-CP screw with yellow-zinc coating is designed for general interior applications, including cross-laminated timber and mass timber construction. For exterior or treated-lumber environments, consult Simpson's product lineup for appropriate coating options.

Does the Type-17 point require pre-drilling before installation?

The Type-17 self-drilling point is designed to bore into wood as the screw is driven, eliminating the need for pre-drilling in most timber applications. This speeds up installation and reduces the risk of misaligned pilot holes in structural panel and beam connections.

What is the purpose of the partial threading on this screw?

The partial threading - with 3-1/8 inches of threaded length on a 7-7/8 inch screw - means the unthreaded shank section does not grip the near-side member. As the screw is driven, the threads in the far member pull the two pieces tightly together, creating a firm clamping action without needing external clamps. This is particularly important for panel-to-beam and lap joint connections in mass timber assemblies.

What drive bit is required for this screw?

This screw requires a T40 6-Lobe (Torx-style) driver bit. Using the correct T40 bit ensures full engagement with the drive recess, minimizing cam-out during high-torque installation into structural timber members.

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