Koelner construction wood screw 3.5x40 mm, countersunk head, TX drive

Koelner construction wood screw 3.5x40 mm with a countersunk head and TX drive is designed for secure wood-to-wood fastening where a flush finish is required. The screw’s 3.5 mm diameter and 40 mm length make it suitable for typical carpentry and construction tasks such as furniture assembly, framing and decking. The conical countersunk head allows the fastener to sit level with the wood surface after installation using a TX (Torx) driver, reducing the need for additional finishing work.

Advantages

This Koelner screw offers reliable holding power in timber due to its thread geometry and appropriate length for common structural joins. The TX drive provides improved torque transfer and reduced cam-out compared with standard Phillips or slotted drives, enabling faster installation with power drivers and more control with manual drivers. The countersunk head provides a neat, flush appearance and minimizes interference with other components or surfaces.

Suitable for

• Furniture assembly and cabinetry
• Decking boards and substructure connections
• Wall and roof framing
• General wood-to-wood joints in structural and finishing carpentry

Key specifications

• Diameter: 3.5 mm
• Length: 40 mm
• Head type: Countersunk (conical) head for flush finish
• Drive type: TX (Torx) drive for improved torque transfer
• Application: Wood-to-wood fastening for structural and finishing tasks

How to use

Pre-drilling is recommended in hardwoods or close to edges to prevent splitting; choose a pilot hole diameter appropriate for the wood species and screw size. Use a TX driver bit matched to the drive recess to ensure correct engagement. Drive the screw until the head sits flush with the wood surface; avoid over-tightening which can strip the drive recess or sink the head too deep. For repeated installations with a power driver, use controlled torque settings to maintain consistent results.

Usage recommendations

Use corrosion-resistant screws or appropriate surface treatments when fastening exterior timber or when the screw will be exposed to moisture. Select pilot hole size and driving speed according to the wood hardness to reduce splitting and ensure optimal holding strength.