Simpson Strong-Drive SDCF TIMBER-CF Screw (0.315 x 4-3/4 in.) is a heavy-duty structural fastener engineered for cross-laminated timber construction, mass timber applications, and general interior use. Featuring a 0.315-in. body diameter and fully-threaded design with a proprietary point, this screw delivers fast, reliable starts and exceptional withdrawal resistance in demanding structural connections. The yellow-zinc coating provides clean, finished-looking installations, while the flat head with underhead nibs ensures flush, precise countersinking in CLT panels and mass timber assemblies. Designed exclusively for interior and dry environments, this structural wood screw is built to meet the performance standards required in modern timber construction.

Key Features

• 0.315-in. shank diameter with fully-threaded design - maximizes thread engagement along the full 4-1/4-in. thread length, delivering uncompromised withdrawal resistance in structural timber connections.
• Flat head with underhead nibs - the nibs bite into the wood surface during installation, enabling clean, flush countersinking without pre-drilling a countersink pocket, saving time and producing a tidy finished surface.
• Proprietary unique point geometry - allows fast, self-starting penetration into timber without pre-drilling, reducing installation time in cross-laminated timber and mass timber applications.
• T40 6-Lobe drive type - provides high torque transfer and superior bit engagement, reducing cam-out and driver slippage during installation for a more controlled, efficient drive.
• Yellow-zinc coated finish - protects the fastener during installation and provides a consistent, professional appearance suited for interior structural assemblies and dry applications.
• 4-3/4-in. overall length with 4-1/4-in. thread length - designed to achieve deep thread engagement in timber panels and glulam members, optimizing load transfer and connection strength.
• 0.590-in. head diameter - the larger head footprint distributes load over a wider bearing area, reducing the risk of pull-through in structural timber panels.

Why This Product

• Purpose-built for cross-laminated timber (CLT) and mass timber construction - where structural integrity and precision fastening are non-negotiable, this screw is specifically designed for the wood species thicknesses and grain orientations common in modern timber framing.
• Fully-threaded along 4-1/4 in. of its 4-3/4-in. length - this means virtually the entire fastener is working to resist withdrawal forces, making it a stronger choice compared to partial-thread screws in structural timber joints.
• The self-starting proprietary point eliminates the need for pre-drilling in many applications - reducing labor steps, speeding up installation, and lowering the risk of timber splitting near panel edges.
• The large flat head with nibs countersinks cleanly under load - giving installers a flush, finished surface without additional prep work, which is especially valuable in exposed mass timber architectural applications.

Specifications

• Brand: Simpson Strong-Tie
• Coating: Yellow-Zinc Coated
• Finish: Yellow-Zinc Coated
• Drive Type: T40 6-Lobe
• Head Type: Flat Head with Nibs
• Head Diameter (in.): 0.590
• Length (in.): 4 3/4
• Shank Diameter (in.): 0.230
• Thread Length (in.): 4 1/4
• Country of Origin: Austria

Available Pack Options

• SDCF22434-R50: 50 Pk - includes one T40, 6-lobe driver bit (replacement bit: BIT40T-134-R2)
• SDCF22434: 250 Pk - includes two T40, 6-lobe driver bits (replacement bit: BIT40T-134-R2)

Approved Applications

• Cross-laminated timber (CLT) construction
• Mass timber construction
• General interior structural applications
• Interior and dry environment installations only

Frequently Asked Questions

Is this screw suitable for outdoor or wet environments?

No. The Strong-Drive SDCF TIMBER-CF screw is designed for interior and dry applications only. It should not be used in exterior, wet, or high-humidity environments where long-term moisture exposure is expected.

Does this screw require pre-drilling before installation?

The proprietary unique point on this screw is designed to provide fast starts and excellent withdrawal resistance, which reduces or eliminates the need for pre-drilling in many mass timber and cross-laminated timber applications. Always follow the applicable installation guidelines for your specific project conditions.

What drive bit is required for this screw?

This screw uses a T40 6-Lobe drive type. A T40 Torx-compatible driver bit is required for proper installation and to achieve full torque transfer without cam-out.

What is the difference between the shank diameter and the head diameter?

The shank diameter is 0.230 in., which is the body of the screw below the head. The overall structural diameter is 0.315 in. The head diameter is larger at 0.590 in., which provides a wider bearing surface that helps distribute load and resist pull-through in timber panel connections.