The Simpson Strong-Drive SDCF TIMBER-CF Screw (0.315 in. diameter x 7 in. length) is a heavy-duty structural fastener engineered specifically for cross-laminated timber (CLT) construction, mass timber assemblies, and general interior wood applications. Featuring a yellow-zinc coated, fully-threaded shank and a proprietary point design, this screw delivers fast, clean installation with exceptional withdrawal resistance - making it a trusted choice for demanding structural timber connections. The large flat head with underhead nibs countersinks cleanly and flush, leaving a professional finish in exposed or concealed timber surfaces.

Key Features

• 0.315 in. shank diameter with 6 5/8 in. thread length - deep, full-thread engagement through thick timber layers delivers uncompromised withdrawal strength in structural CLT and mass timber applications
• Flat head with underhead nibs - the nibs bite into the timber surface for clean, consistent countersinking without pre-drilling, creating a flush finish that meets structural and aesthetic requirements
• T40 6-Lobe drive type - the six-lobe torque interface resists cam-out under high-torque installation, giving installers more control and fewer stripped drive recesses in dense structural timber
• Proprietary unique point design - engineered for fast starts and self-drilling entry into timber, reducing pre-drilling needs and speeding up installation in cross-laminated and mass timber construction
• Yellow-zinc coating, fully threaded - consistent corrosion protection for interior and dry service environments, combined with full-length threading for maximum holding power along the entire fastener length
• 0.590 in. head diameter - the wide bearing surface distributes load across the timber face, reducing the risk of head pull-through in structural loading scenarios

Why This Product

• Purpose-built for CLT and mass timber - unlike general-purpose wood screws, the SDCF TIMBER-CF is specifically designed for cross-laminated timber and mass timber construction, where structural integrity and precise fastener geometry are critical to performance
• Withdrawal resistance without compromise - the combination of full threading over 6 5/8 in. of the 7 in. length and a 0.315 in. shank diameter means this fastener holds firmly in thick timber assemblies where load demands are highest
• Clean countersinking in a single step - the flat head with integral underhead nibs seats flush without additional prep work, making it practical for high-volume timber construction where speed and finish quality both matter
• High-torque drive system reduces installation error - the T40 6-Lobe recess handles the elevated torque required to drive a 0.315 in. fastener into dense structural timber, minimizing stripped drives and rework on the job site

Specifications

• Brand: Simpson Strong-Tie
• Length: 7 in.
• Shank Diameter: 0.230 in.
• Head Diameter: 0.590 in.
• Thread Length: 6 5/8 in.
• Head Type: Flat Head with Nibs
• Drive Type: T40 6-Lobe
• Coating: Yellow-Zinc Coated
• Finish: Yellow-Zinc Coated
• Country of Origin: Austria

Available Pack Options

• SDCF22700-R50: 50 Pk - includes one T40, 6-lobe driver bit (replacement bit: BIT40T-134-R2)
• SDCF22700: 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 wood applications
• Interior and dry service environments only

Frequently Asked Questions

Is the SDCF TIMBER-CF screw suitable for outdoor or wet environments?

No. The Strong-Drive SDCF TIMBER-CF screw with yellow-zinc coating is designed for interior and dry applications only. It is not rated for exterior, wet, or pressure-treated lumber environments where a higher-rated corrosion-resistant coating would be required.

What bit do I need to drive this screw?

This screw requires a T40 6-Lobe (star-type) driver bit. The T40 size is matched to the fastener's drive recess and is necessary to handle the torque required for driving a 0.315 in. diameter screw into structural timber without cam-out.

Does this screw require pre-drilling?

The SDCF TIMBER-CF features a proprietary unique point designed for fast starts and self-entry into timber, which helps eliminate the need for pre-drilling in many applications. The underhead nibs also allow the flat head to countersink cleanly without a separate countersink step.

What is the difference between the shank diameter and the listed product diameter?

The product is identified by its 0.315 in. nominal diameter, which reflects the overall fastener sizing used for structural specification purposes. The measured shank (unthreaded) diameter is 0.230 in., while the threaded portion engages over 6 5/8 in. of the 7 in. total length to maximize withdrawal resistance in timber assemblies.