Koelner/Rawlplug construction screws 4.0x40 mm are self-tapping fasteners with a partial thread and a countersunk (conical) head designed for flush mounting. Supplied in a pack of 24 pieces, these screws combine an unthreaded shank portion for clamping with a threaded tip for secure engagement in wood and other soft substrates. They are intended for structural joinery, furniture assembly and general woodworking tasks where a recessed head and a shank that allows tight clamping are required.
Advantages
These construction screws feature a partial thread that permits the unthreaded shank to act as a clamp, pulling joined parts tightly together while the threaded section secures into the substrate. The countersunk head allows the screw to sit flush with or below the material surface for a neat finish and easier finishing. Being self-tapping, they reduce the need for pre-drilling in many wood and composite applications, speeding up assembly and reducing labour time.
Suitable for
- Joining wooden elements in structural and non-structural assemblies
- Furniture assembly where recessed screw heads are needed
- Fixing components that require a clamping shank for alignment
When it may not be suitable
These screws are designed primarily for wood and similar soft materials; they may not be appropriate for use in hard metals, masonry or concrete without the correct plug or anchor. For applications requiring corrosion resistance in outdoor or marine environments, a screw with a dedicated corrosion-resistant coating or stainless steel material should be considered instead.
Key specifications
- Diameter: 4.0 mm
- Length: 40 mm
- Thread type: partial/incomplete thread with a threaded tip
- Head style: countersunk (conical) head for flush mounting
- Drive type: (compatible with standard screwdriver/drill drives typical for construction screws)
- Quantity: 24 pieces per pack
How to use
Position the screw so the unthreaded shank spans the gap between the two components to be clamped, then start driving the screw so the threaded tip engages the receiving material. Apply steady torque until the countersunk head sits flush with the surface; avoid over-torquing which can damage the material or strip the thread. For harder materials or thicker sections, pilot holes may be drilled to ensure accurate alignment and prevent splitting. Use an appropriate driver bit and a controlled-speed drill or screwdriver for best results.
What to consider before purchase
- Verify material compatibility — designed primarily for wood and wood-based composites
- Confirm the required length and diameter match the thickness of joined materials
- Assess whether additional corrosion resistance is needed for outdoor use
Usage recommendations
For consistent results, clamp or support workpieces before driving screws, use the correct driver bit, and check screw seating frequently to prevent over-penetration. When installing into edge zones, consider pre-drilling to avoid splitting; in exterior applications choose fasteners with appropriate corrosion protection.
